To obtain the aluminum alloy with high thermal and mechanical properties, the effects of alloying elements and the second phases on the thermal conductivity of Al alloys were investigated by CALPHAD and first-principles calculation, respectively. The properties of the second phases, including Young's modulus, Poisson's ratio and minimum thermal conductivity, were systematically studied. Results show that the ranking order of the effects of the alloying elements on the thermal conductivity is Mg>Cu>Fe>Si, and for Al-12Si alloys, the mathematical model of the relationship between the alloying elements and the thermal conductivity can be expressed as λ=ax²-bx+c when the second phase precipitates in the matrix. All kinds of ternary phases of Al-Fe-Si have higher deformation resistance, rigidity, theoretical hardness, Debye temperature and thermal conductivity than the other phases which possibly exist in the Al-12Si alloys. Based on the guidance of CALPHAD and first-principles calculation, the optimized chemical composition of Al alloy with high conductivity is Al-11.5Si-0.4Fe-0.2Mg (wt.%) with a thermal conductivity of 137.50 Wm^-1·K^-1 and a hardness of 81.3 HBW.

为满足电动汽车动力电池组耐撞性设计的要求，对不同机械滥用工况下锂离子电池单体的失效机理进行了试验研究。通过对三种不同容量的NCR18650圆柱形锂离子电池进行局部压痕和平面压缩加载试验，研究了锂离子电池样本的力-电-热响应，给出了失效电池样本的横截面破坏形式，具体讨论了加载形式和电池容量对锂离子电池失效的影响。研究结果表明，局部压痕和平面压缩将导致电池分别出现内短路和外短路两种触发失效模式。随着额定容量的提高，电池的承载能力降低，从而导致失效位移减小。机械加载形式和额定容量亦对电池表面温度变化有重要影响，局部压痕失效后电池达到的最高表面温度较高，中等容量电池的表面温度变化相对平稳。

To refine the microstructure and improve the mechanical properties of AZ91D alloy by expendable pattern shell casting (EPSC), the mechanical vibration method was applied in the solidification process of the alloy. The effects of amplitude and pouring temperature on microstructure and mechanical properties of AZ91D magnesium alloy were studied. The results indicated that the mechanical vibration remarkably improved the sizes, morphologies and distributions of the primary α-Mg phase and β-Mg₁₇Al₁₂ phase, and the densification and tensile properties of the AZ91D alloy. With an increase in amplitude, the microstructures were gradually refined, resulting in a continuous increase in mechanical properties of the AZ91D alloy. While, with the increase of pouring temperature, the microstructures were continuously coarsened, leading to an obvious decrease of the mechanical properties. The tensile strength and yield strength of the AZ91D alloy with a vibration amplitude of 1.0 mm and a pouring temperature of 730℃ were 60% and 38% higher than those of the alloy without vibration, respectively.

为了提高表贴式永磁同步电机的电流环频率响应能力和转速响应性能，针对其无源控制器设计过程中因d轴、q轴电流存在耦合而造成期望互联矩阵未知参数过多的问题，结合电压前馈解耦控制，提出了一种基于电流解耦的无源控制器新型设计方法。首先，根据能量平衡原理和电压前馈解耦控制，构建基于电流解耦的表贴式永磁同步电机端口受控耗散哈密顿系统（port control Hamilton system with dissipation, PCHD）模型。然后，通过互联和阻尼配置的无源控制（interconnection and damping assignment passivity-based control, IDA-PBC）方法，完成表贴式永磁同步电机无源控制器的设计，并在设计过程中引入了电压前馈解耦控制，消除了d轴、q轴电流的耦合关系，使期望互联矩阵的未知参数由3个减少为1个。最后，搭建表贴式永磁同步电机测试平台进行实验验证。实验结果表明，当表贴式永磁同步电机的电流环采用基于电流解耦的无源控制器时，q轴电流响应频率由小于250 Hz增大为大于333 Hz；额定转速下的转速响应时间由0.16 s减小为0.11 s，超调量由2.0%减小为0.6%，稳态误差由5.98 r/min减小为1.15 r/min。研究结果可为永磁同步电机的无源控制器设计提供新思路。

Based on STL (stereo lithography) format file and with Microsoft Visual C⁺⁺ 6.0 programming language,a 3D printing slicing software appropriate for the surface strengthening of the parts has been developed,which includes three functions:3D model import,model slicing and data export.Through the grouping of STL model triangle facets before slicing,the judgment times of the relationship between the triangle facets and the cutting planes are reduced,and the slicing efficiency is improved.Aiming at the fact that the surface should be strengthened when the part is formed by using of 3D printing process,the function of identifying and marking the surface of the geometric entity is accomplished in the slicing software,which can strengthen the surface of the part according to the user’s requirements.The developed slicing software can provide an entity slicing file for 3D printing equipment.The related functions can be adjusted and improved according to user’s needs,which makes the software convenient and flexible to use.

In the process of hot-dip Zn-Al-Mg alloy coating, the plating solution dissipates heat in the direction perpendicular to the steel plate, which is considered to be a process of directional solidification. To understand the relationship between microstructure and cooling rate of Zn-Al-Mg alloys, both the phase constitution and microstructure characteristic length scales of Zn-9.5Al-3Mg-0.01Ce (wt.%) alloy were investigated by the directional solidification experiments at different growth velocities (V=40, 80, 160, 250 μm·s^-1). The experimental results show that the microstructure of directionally solidified Zn-9.5Al-3Mg-0.01Ce alloy is composed of primary Al dendrites and (Zn-Al-Mg₂Zn₁₁) ternary eutectics at the growth velocities ranging from 40 to 250 μm·s^-1. The primary Al dendrites are aligned regularly along the growth direction, accompanied with obvious secondary dendrites. The relationship between the microstructure length scale and the thermal parameters of solidification is obtained: λ₁=374.66V^-0.383, and λ₂=167.5V^-0.563 (λ₁ is the primary dendrite arm spacing, and λ₂ is the secondary dendrit arm spacing). In addition, through the interface response function (IRF) and the nucleation and constitutional undercooling (NCU), the phase selection of Zn-9.5Al-3Mg-0.01Ce is obtained: (Zn+Al+Mg₂Zn₁₁) ternary eutectics in the Zn-9.5Al-3Mg-0.01Ce alloy will be replaced by ternary eutectics (Zn+Al+MgZn₂) when the growth rate is lower than 7.53 μm·s^-1.

目前智能技术自身在通用性、稳健性、安全性等方面并不成熟，智能交互产品极易因在意图表达、信息处理、决策逻辑、交互时序、动作强度等方面与用户行为模式的不匹配而产生“行为冲突”，人机环境系统多领域行为过程的统一建模与优化是实现智能交互产品行为特性调控和正向设计的关键。从如何表征、用什么表征、如何校验、如何优化四个维度系统地梳理了人机环境系统多领域行为过程表征模型、建模语言/工具、模型验证和行为过程优化等方面的研究进展，分析了目前该领域存在的问题和局限性，展望了未来的研究重点和发展趋势。

AZ91D and 8.5vol.% SiC_p/AZ91D magnesium matrix composites were fabricated by a semi-solid extruded processing method,and treated with solution and aging heat treatment.The effects of SiC_p on the microstructures of the semi-solid extruded AZ91D magnesium alloy during recrystallization were studied by observing and analyzing the microstructure evolution during extrusions and heat treatments.The results show that the addition of SiC_p inhibits the dynamic recrystallization of AZ91D during the semi-solid extrusion with only 26% of the volume fraction of recrystallization.Furthermore,the addition of SiC_p refines the sizes of grains and second phases,and upgrades the volume fraction of second phase.After solution and aging treatment,the recrystallization continues,and the addition of SiC_p promotes the recrystallization and the recrystallized microstructure is much more stable.Meanwhile,the sizes of grains and second phases continue to be refined,and the volume fraction of second phases continues to increase.

A novel Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy was designed using the cluster formula approach (cluster-plus-glue-atom model) and prepared by laser melting deposition (LMD). Its composition formula 12[Al-Ti₁₂](AlTi₂)+5[Al_0.8Si_0.2-Ti₁₂Zr₂](V_0.8Mo_0.2Nb₁Ti) features an enhanced β-Ti via co-alloying of Zr, V, Mo, Nb and Si. The experimental results show that the cluster formula of α and β phases in the novel alloy are respectively α-[Al-Ti_11.5Zr_0.5](Al₁Ti₂) and β-[Al_0.8Si_0.2-Ti_13.2Zr_0.8](V₁Mo_0.4Nb_1.6), both containing Zr elements. The fitted composition via the α and β phase cluster formulas has little difference with the actual alloy composition, suggesting that the validity of cluster-plus-glue-atom model in the alloy composition design. After hot isostatic pressing (HIP), both the Ti-6Al-4V and the novel alloy by LMD are characterized by prior-β columnar grains, while the typical <100> texture disappears. Compared with Ti-6Al-4V, Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy exhibits a combination of higher strength (1,056 MPa) and higher ductility (14%) at room temperature and higher strength (580 MPa) at 550 ℃ after HIP, and can potentially serves as LMD materials.

为满足下肢运动功能障碍患者在不同阶段的康复训练需求，针对现有下肢康复机器人训练方式单一的问题，提出了一种可实现卧姿、坐姿训练模式的牵引式下肢康复机器人。首先，根据人体下肢运动机理和仿生原理，设计了一种五自由度混联机构构型。然后，建立了机器人的运动学模型，分别计算了其运动学正、逆解。接着，以人体下肢末端与机器人末端的工作空间重合度为目标函数，采用遗传算法对机器人的机构参数进行了优化，并求得人机系统矢状面内人体下肢的有效工作空间比为0.71。最后，规划了CPM（continuous passive motion，连续被动运动）、圆周运动和螺旋运动等3种康复训练运动轨迹，并根据优化后的机构参数搭建了机器人样机，通过运动捕捉实验验证了机器人结构设计与优化结果的合理性以及轨迹规划的正确性，表明该机器人能够满足下肢运动功能障碍患者的康复需求。

Hot tearing is one of the most serious defects during the casting solidification process. In this study, a new type of multichannel "cross" hot tearing device was designed. The hot cracks initiation and propagation were predicted by the relationship between temperature, shrinkage force and solidification time during the casting solidification process. The reliability and practicability of the multichannel "cross" hot tearing device were verified by casting experiments and numerical simulations. The theoretical calculation based on Clyne-Davies model and numerical simulation results show that the hot tearing tendency decreases in the order:2024 Al alloy>Al-Cu alloy>Al-Si alloy at a pouring temperature of 670℃ and a mold temperature of 25℃. Feeding of liquid films at the end of solidification plays an important role in the propagation process of hot tearing. The decrease of hot tearing tendency is attributed to the feeding of liquid film and intergranular bridging.

The present study designed two kinds of Fe-18Mn-1.3C-2Cr-(4, 11)Al (wt.%) low-density steels. Tensile and impact tests were carried out to evaluate the work hardening and impact toughness properties via aluminum (Al) alloying control. Meanwhile, microstructure evolution and fracture morphology were investigated by X-ray diffraction (XRD), a scanning electron microscope (SEM) equipped with electron backscatter diffraction (EBSD), a transmission electron microscope (TEM), and a stereo-optical microscope (OM). It is found that the Al addition obviously promotes the dislocation planar slipping, resulting in cleavage and brittle impact fracture in 11wt.% Al steel. Besides, the microband-induced plasticity (MBIP) mechanism is found in 4wt.% Al containing steel, introducing considerable work hardening capacity and impact toughness of 156.8±17.4 J. The present study provides a direct illustration of the relationship between work hardening and impact toughness behaviors of these two low-density steels for potential application as impact-resistant components.

Two important factors affecting the performance of sand mold/core generated by 3D printing (3DP) are strength and dimensional accuracy,which are not only closely related to the reactivity of furan resin and the phase transition of silica sand,but also the curing agent system of furan resin.This paper studies the influence of gel time on the strength and dimensional accuracy of a 3DP sand mold/core,taking the furan resin system as an example and using a sand specimen generated by a 3DP inkjet molding machine.The experiment demonstrates that the gel time of 3 to 6 min for the sand mixture suits 3DP core-making most under the experimental condition.However,it should be noted that under the same resin condition,the strength of a no-bake sand mold/core is higher than that of a 3DP sand mold/core.The dimensional accuracy of the sand mold/core does not change significantly when the gel time is less than 15 min.Improving the activity of binder and developing ultra-strong acid with low corrosion shall be an effective way to improve the quality of the mold/core by 3D printing.

The laser powder bed fusion (L-PBF) method of additive manufacturing (AM) is increasingly used in various industrial manufacturing fields due to its high material utilization and design freedom of parts. However, the parts produced by L-PBF usually contain such defects as crack and porosity because of the technological characteristics of L-PBF, which affect the quality of the product. Laser ultrasonic testing (LUT) is a potential technology for on-line testing of the L-PBF process. It is a non-contact and non-destructive approach based on signals from abundant waveforms with a wide frequency-band. In this study, a method of LUT for on-line inspection of L-PBF process was proposed, and a system of LUT was established approaching the actual environment of on-line detection to evaluate the method applicability for defects detection of L-PBF parts. The detection results of near-surface defects in L-PBF 316L stainless steel parts show that the crack-type defects with a sub-millimeter level within 0.5 mm depth can be identified, and accordingly, the positions and dimensions information can be acquired. The results were verified by X-ray computed tomography, which indicates that the present method exhibits great potential for on-line inspection of AM processes.

Aero-engine hollow turbine blades are work under prolonged high temperature, requiring high dimensional accuracy. Blade profile and wall thickness are important parameters to ensure the comprehensive performance of blades, which need to be measured accurately during manufacturing process. In this study, a high accuracy industrial computed tomography (ICT) measuring method was developed based on standard cylindrical pin and ring workpieces of different sizes. Combining ICT with cubic spline interpolation, a sub-pixel accuracy was achieved in measuring the dimension of component. Compared with the traditional and whole-pixel level image measurement method, the cubic spline interpolation algorithm has the advantages of high accuracy in image edge detection and thus high accuracy of dimensional measurement. Further, the technique was employed to measure the profile and wall thickness of a typical aerospace engine turbine blade, and an accuracy higher than 0.015 mm was obtained.

针对单柱塞泵系统中配流单向阀参数不合理所导致的吸油不充分、系统响应慢等问题，提出了一种基于线性回归的多参数优化方法。首先，通过AMESim软件进行单柱塞泵系统仿真分析，并利用MATLAB拟合工具箱分别探讨了不同单向阀参数（弹簧预紧力、弹簧刚度和阀芯质量）与进油口流量的关系。然后，在利用主成分分析法消除各参数之间相关性的基础上，以进油口流量为因变量，弹簧预紧力、弹簧刚度和阀芯质量为自变量，各参数的取值范围为约束条件，建立了基于线性回归的单向阀参数优化模型，并采用遗传算法进行优化求解。最后，根据优化前后的单向阀参数，对单柱塞泵系统进行仿真分析和实验验证。仿真结果表明，优化后进油口流量提高了21.3%；实验结果表明，优化后进油口的实际流量提高了16.8%。研究表明，所提出的多参数优化方法是一种有效的方法，可为单柱塞泵系统中配流单向阀的参数优化提供参考。

Effect of solution treatment on microstructure and mechanical properties of Al-12Si-4Cu-2Ni-0.8Mg-0.2Gd alloy was investigated. Results show the Si particles become stable and more intermetallic compounds dissolve in the matrix after solution treatment at 500℃ for 2 h followed by 540℃ for 3 h (T4). The skeleton-like Al₃CuNi develops into two parts in the T4 alloy:one is Al₃CuNi which has the framework shape; the other is intermetallics including the Al₃CuNi (size:5-10 μm) and AlSiCuNiGd phases (size: ≤ 5 μm) with complex structure. Adding 0.2% Gd can improve the mechanical properties of the alloys after two-step solution treatment (500℃/2 h followed by 540℃/3 h), the hardness of the alloy increases from 130.9 HV to 135.8 HV compared with the alloy with one-step solution treatment (500℃/2 h), the engineering strength increases from 335.45 MPa to 352.03 MPa and the fracture engineering strain increases from 1.44% to 1.67%.

为满足角盒类零件型腔特征识别需求，提出了一种基于改进图匹配的型腔特征自动识别方法。分析了角盒类零件型腔特征，提取了特征简化模型的共性模板属性。获取了模型栅格高度点云数据，以高度中值作为阈值并将其转换为0-1特征值矩阵，提取了型腔面投影特征值以分离识别型腔壁边面。采用共性模板面邻接属性判定搜索型腔侧壁面，最终识别出了包含底板面集、壁边面集和侧壁面集的完整型腔加工特征。实例验证结果表明，相较于固定模板匹配的特征识别方式，采用所提方法识别角盒类零件型腔加工特征时具有更高的效率和更好的鲁棒性。

随着3D打印零件复杂性和多样性的日益增加，单一材质的零件已无法满足各类特殊性能要求，功能梯度材料零件逐渐成为快速成型制造行业的研究热点。为满足功能梯度材料的制造要求，提出了一种基于坐标变换的功能梯度材料空间映射建模方法，该方法的关键是将几何信息与材料信息有效结合。首先，采用单梯度源法、多梯度源法构建功能梯度材料模型的材料空间，在遇到交叉梯度源模型时利用特定的相交算子以一定的权重比进行材料分布计算。然后，在几何空间与材料空间结合的过程中，巧妙地通过坐标变换将材料空间与几何空间的坐标系重合，实现将材料空间映射至几何空间，从而得到带有材料信息的功能梯度材料模型。通过修改梯度源、材料分布函数以及坐标变换方法即可获得所需的功能梯度材料模型。利用Visual Studio 2019软件和OpenGL编程语言对实例模型进行可视化分析的结果表明，所提出的建模方法相比于大部分估值建模、非估值建模方法可大大缩短建模时间，从根本上解决了某些算法所造成的储存空间不足和建模过程繁琐等问题。基于坐标变换的功能梯度材料空间映射建模方法为增材制造行业提供了一种新的建模方法，具有良好的应用价值。

Zr-based metallic glasses (MGs) possess a wide supercooled liquid region, which gives a wide processing window for superplastic forming to make microdevices with demanding size accuracy and surface finishing. The existence of oxygen may have an influence on the thermoplastic deformation process. Therefore, the effect of oxidation on the mechanical behavior of the MGs in the vicinity of glass transition temperature is of great significance for practical forming of MG components. In the present study, the effect of oxidation on tensile properties of Zr₅₀Cu₄₀Al₁₀ metallic glass was investigated. The tested samples were characterized by XRD and SEM analysis. For the samples tested in air, the strength decreases 187 MPa, 61 MPa and 59 MPa and the ductility increases 0.31, 0.36, and 0.77 at 420 ℃, 430 ℃, and 440 ℃, respectively, compared with those tested in flowing argon. ZrO₂ preferentially formed during the tensile testing at 420 ℃, and both ZrO₂ and Al₂O₃ oxides formed at 430 ℃. The dilution of Zr elements in the remaining amorphous matrix caused by preferential oxidation on the surface layer attributes to the decrease in strength and enhancement in ductility of the Zr₅₀Cu₄₀Al₁₀ metallic glasses.

Numerical simulation technology has been widely used in the foundry industry to analyze and improve casting processes. During the casting filling process, many filling-related defects form easily at the confluences of liquid metal streams. The main filling-related defects are cold shut defects. To calculate the positions of casting defects, the characteristics of liquid metal confluences were analyzed. The flow front of liquid metal was captured by the volume-of-fluid algorithm to obtain a time field, which was used to calculate the time derivatives of the liquid front position and the confluences of liquid metal streams. To distinguish small confluences from the main confluences, the concept of confluent scale was developed, which was used to filter the small confluences based on a threshold. The calculation process was demonstrated through the post-processing of numerical simulation. A "W" shaped casting and a steering wheel casting were calculated to validate the accuracy of the method developed in this study. The positions of cold shut defects were predicted by calculating the confluences of liquid metal streams. The method was proved to be practical by comparing the calculation results with the positions of cold shut defects in an end cover casting. The computation of confluences and cold shut defects can improve the analysis efficiency and provide assurance for the optimization of a casting process plan.

K439B nickel-based superalloy is a new type of high-temperature material. There is insufficient research on its constitutive equations and numerical modeling of thermal stress. Isothermal tensile experiments of K439B superalloy at different temperatures (20 ℃-1,000 ℃) and strain rates (1.33×10^-3 s^-1-5.33×10^-3 s^-1) were performed by using a Gleeble-3800 simulator. The elastic moduli at different temperatures (20 ℃-650 ℃) were measured by resonance method. Subsequently, stress-strain curves were measured for K439B superalloy under different conditions. The elastic-viscoplastic constitutive equations were established and the correspongding parameters were solved by employing the Perzyna model. The verification results indicate that the calculated values of the constitutive equations are in good agreement with the experimental values. On this basis, the influence of process parameters on thermal stress was investigated by numerical simulation and orthogonal experimental design. The results of orthogonal experimental design reveal that the cooling mode of casting has a significant influence on the thermal stress, while pouring temperature and preheating temperature of shell mold have minimal impact. The distribution of physical fields under optimal process parameters, determined based on the orthogonal experimental design results, was simulated. The simulation results determine separately the specific positions with maximum values for effective stress, plastic strain, and displacement within the casting. The maximum stress is about 1,000.0 MPa, the plastic strain is about 0.135, and the displacement is about 1.47 mm. Moreover, the distribution states of thermal stress, strain, and displacement are closely related to the distribution of the temperature gradient and cooling rate in the casting. The research would provide a theoretical reference for exploring the stress-strain behavior and numerical modeling of the effective stress of the alloy during the casting process.

The total content of Al and Ti in advanced Ni-based wrought superalloys is up to 7.5wt.%, which makes it easier to form harmful nonequilibrium eutectic (γ+γ') and η phase. It has been reported that the addition of certain amount of Zr can modify precipitation of the nonequilibrium phases obviously, but the mechanism is still controversial. The effect of Zr ranging from <0.0006wt.% to 0.150wt.% on solidification behavior, segregation and microstructure of a Ni-based superalloy with high Al and Ti contents was investigated, eliminating the interferences of C and B. Results show that increase in Zr content significantly promotes the formation of eutectic (γ+γ'), η and Zr-rich phase in the interdendritic region. Besides the Zr-rich phase, Zr dissolves slightly in the eutectic γ' and obviously in the η phase. An interesting phenomenon is discovered that the Zr addition significantly increases the area fraction of liquid pools and enlarges the forming range of γ dendrites, which suggests that Zr markedly retards the solidification. Zr affects the eutectic (γ+γ') and η formation mainly due to the retard of solidification and dissolution of Zr in them. The retard of solidification obviously increases the residual liquid fraction and undercooling. Zr can serve as a forming element for the eutectic (γ+γ') and η phase, and the obvious dissolution of Zr in η phase significantly decreases the critical concentration of Ti for its precipitation.

Boron and carbon contents are the main factors influencing the properties of high-boron steel. In this study, experimental samples with different boron-to-carbon ratios (%B/%C) were prepared. The microstructures of the different samples were observed, and their hardness, bending strength, and impact toughness were investigated. Results show that the main microstructures in the investigated high-boron steel samples are the eutectic Fe₂B structure with a fishbone shape and the ternary peritectic Fe₃(C, B) structure with a chrysanthemum shape. When the boron content is 2.5wt.% and the carbon content is 0.43wt.% (i.e., %B/%C=5.82), the overall mechanical properties of the alloy are the best. The alloy’s hardness, bending strength and impact toughness reach their maximums, which are 67.3 HRC, 1,267.36 MPa and 6.19 J·cm^-2, respectively. The optimized alloy is compared with conventional materials exhibiting excellent wear resistance (namely, high-manganese steel and high-chromium cast iron) through two-body and three-body abrasion tests. The wear resistance of this high-boron steelinvestigated in this work is found to be superior to those of the more common materials.

Microstructure, mechanical properties and phase transformation of a heat-resistant rare-earth (RE) Mg-16.1Gd-3.5Nd-0.38Zn-0.26Zr-0.15Y (wt.%) alloy were investigated. The as-cast alloy is composed of equiaxed α-Mg matrix, net-shaped Mg₅RE and Zr-rich phases. According to aging hardening curves and tensile properties variation, the optimized condition of solution treatment at 520 ℃ for 8 h and subsequent aging at 204 ℃ for 12 h was selected. The continuous secondary Mg₅RE phase predominantly formed at grain boundaries during solidification transforms to residual discontinuous β-Mg₅RE phase and fine cuboid REH₂ particles after heat treatment. The annealed alloy exhibits good comprehensive tensile property at 350 ℃, with ultimate tensile strength of 153 MPa and elongation to fracture of 6.9%. Segregation of RE elements and eventually RE-rich precipitation at grain boundaries are responsible for the high strength at elevated temperature.

Ti-Ni composite sub-micron powders with different compositions were prepared by vacuum melting and atomization technology. These powders, after being mixed with a solution of phenolic resin and alcohol, were applied on the mold cavity wall, by which a casting-infiltration layer was introduced on the surface of ZG45 steel via reactions between the powders and molten steel under the heat released by solidification. The effects of the powders’ composition and pouring temperature on the corrosion resistance of the casting-infiltration layer were studied. An optimal casting-infiltration layer with a thickness of ～7 mm was obtained by infiltrating the Ti-Ni composite powders containing 35wt.% Ti to ZG45 steel pouring at 1,650 ℃. The casting-infiltration layer has a good metallurgic bonding with the matrix, and is mainly composed of Fe₂Ti phase and continuous γ-(Fe, Ni) solid solution. In the corrosive H₂SO₄ solution, the corrosion potential of the casting-infiltration layer is lower than the matrix, tending to form a passivation film, which lowers the dissolution rate especially when the potential rises to 0.50 V. After dipping in the 10wt.% NaCl solution for 480 h, a lot of corrosion holes appear in the ZG45 steel matrix, while there are no obvious traces of corrosion on the casting-infiltration layer.

针对空间站舱体水平旋转装备负载30 t后在长度方向上易产生变形的问题，提出了六点调平算法及同步控制方法。在原有空间站舱体水平旋转装备的4个边角处各安装1条螺旋升降支腿的基础上，在2条长边的中心位置处各增加1条螺旋升降支腿，通过协同控制各螺旋升降支腿的高度，使得水平旋转装备上平面的水平度达到0.001°以内，以确保空间站舱体的质心稳定以及结构不发生变形。同时，利用理论仿真验证了六点调平算法及同步控制方法的可行性。经实验测试，所提出方法的调平效果良好，6条螺旋升降支腿的同步控制误差小于8 ms；调平后水平旋转装备上平面水平度的最大误差为0.000 8°，最大变形量为0.074 mm，可忽略不计，符合预期目标。结果表明，六点调平算法及同步控制方法的应用有效避免了空间站舱体水平旋转装备负载30 t后在长度方向上产生变形的问题，提高了水平旋转装备的水平度并延长了其使用寿命，同时确保了空间站舱体放置在水平旋转装备上后质心稳定，这可为后续的空间站总装过程提供技术保障。

The application of additive manufacturing technology is one of the main approaches to achieving the rapid casting. Additive manufacturing technology can directly prepare casting molds (cores) with no need of patterns, and quickly cast complex castings. The combination of additive manufacturing and traditional casting technology can break the constraint of traditional casting technology, improve casting flexibility, and ameliorate the working environment. Besides, additive manufacturing promotes the realization of "free casting", greatly simplifying the processing procedures and shortening the manufacturing cycle. This paper summarizes the basic principle of additive manufacturing technology and its development situation domestically and overseas, mainly focusing on the development status of several main additive manufacturing technologies applicable to the foundry field, including three-dimensional printing, selective laser sintering, stereolithography, layered extrusion forming, etc. Finally, the future development trend of additive manufacturing technology in the foundry field is prospected.

Fused corundum is a rather promising raw material for preparing an alumina-based ceramic core due to its excellent high temperature resistance and chemical inertness.In this study,alumina-based ceramic cores were prepared using fused corundum as the matrix material,and the effect of varying silica powder contents on the properties of the alumina-based ceramic cores,including the sintering shrinkage,the flexural strength,and the high temperature deformation was investigated.The mineralization mechanisms of the silica on the alumina-based ceramic core were also analyzed.The optimum addition amount of silica in this experiment is 8% in weight.At that moment,the aluminum-based core has both a low sintering shrinkage coefficient of 0.66% and better properties:the room temperature flexural strength is 22.19 MPa,the high temperature flexural strength is 21.54 MPa,the high temperature deformation is 0.93 mm,and the residual flexural strength is 47.41 MPa.

The infiltration casting fabrication process based on spherical CaCl₂ space-holders and the compressive behavior including the mechanical performance and energy absorption capacity of open-cell aluminum foams were investigated. Open-cell aluminum foams with different porosities in the range of 63.1% to 87.3% can be fabricated by adjusting compression ratios of CaCl₂ preforms prepared by precision hot-pressing. The compression tests show that a strain-hardening phenomenon always occurs especially for open-cell aluminum foam with low porosity, resulting in the inclining stress-strain curve in the plateau region. The energy absorption capacity of open-cell aluminum foam decreases with increasing porosity when compared at the same strain. However, when compared at a given stress, each foam can absorb the maximal energy among the five foams in a special stress range. Additionally, open-cell aluminum foam possesses the maximum energy absorption efficiency at its optimum operating stress. At this stress condition, the foam can absorb the highest energy compared with other foams at the same stress point. The optimum operating stress and the corresponding maximal energy absorption decrease with increasing the porosity. The optimum operating stress for energy absorption can also be determined similarly when taking into consideration of the lightweight extent of foams.

Al-5Ti-B and Al-5Ti-B-Gd master alloy refiners were fabricated by fluorine salt casting method. The microstructure and phase constitution of the master alloys were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that Al-Ti-B alloy refiner consists of Al₃Ti phase and TiB₂ phase. After Gd is introduced into the intermediate alloy, Ti₂Al₂₀Gd phase appears in the alloy, the size of Al₃Ti is significantly reduced, and Ti-Al-Gd phase is found in the edge of Al₃Ti phase. At the same time, some independent Ti-Al-Gd phases appear in local areas, which are Ti₂Al₂₀Gd phase determined by micro-area electron diffraction analysis. Analysis and calculation results of the high-resolution images of the Ti₂Al₂₀Gd/Al structure show that there is no other compound at the junction between the Ti₂Al₂₀Gd phase and Al, and Ti₂Al₂₀Gd phase has a great difference in atomic space with the α-Al, which cannot be directly used as heterogeneous nucleus. But, after being decomposed in the aluminum melt, the Ti₂Al₂₀Gd phase can promote the refinement effect of the refiner. In the Al-Ti-B-Gd master alloy, there are many dispersed Al₃Ti particles with a size of less than 1 μm, which can promote the Al-5Ti-B refining effect.

The initiation and propagation of thermal fatigue cracks in gray cast iron and vemicular graphite cast iron were investigated by Uddeholm method to reveal the complex thermal fatigue behaviors of cast iron. Differences of thermal fatigue behaviors of gray cast iron and vemicular graphite cast iron were observed and analyzed. It is found that the observed differences are related to the combination of graphite morphology and the oxidization of matrix. More oxidized matrix is observed in gray cast iron due to its large specific surface area. The brittle oxidized matrix facilitates the propagation of microcracks along the oxidization layer. By contrast, the radial microcracks are formed in vermicular graphite at the edge of graphite due to fewer oxidization layers. It indicates that the thermal fatigue resistance of gray cast iron is dominated by graphite content and morphology while that of vermicular graphite cast iron strongly relates to the strength of the matrix.

The two-phase zone continuous casting (TZCC) technique was used to continuously cast high-strength aluminum alloy hollow billets, and a verified 3D model of TZCC was used to simulate the flow and temperature fields at casting speeds of 2-6 mm·min^-1. Hollow billets under the same conditions were prepared, and their macro/microstructures were analyzed by an optical microscope and a scanning electron microscope. During the TZCC process, a circular fluid flow appears in front of the mushy zone, and the induction heated stepped mold and convective heat transfer result in a curved solidification front with depressed region near the inner wall and a vertical temperature gradient. The deflection of the solidification front decreases and the average cooling rate in the mushy zone increases with increasing casting speed. Experimental results for a 2D12 alloy show that hot tearing periodically appears in the hollow billet accompanied by macrosegregation near the inner wall at casting speeds of 2 and 4 mm·min^-1, while macroscopic defects of hot tearing and macrosegregation weaken and the average size of columnar crystals in the hollow billets decreases with further increasing casting speed. 2D12 aluminum alloy hollow billets with no macroscopic defects, the finest columnar crystals, and excellent mechanical properties were prepared by TZCC at a casting speed of 6 mm·min^-1, which is beneficial for the further plastic forming process.

Progressive solidification is usually considered an effective strategy to reduce the hot tearing susceptibility of a cast component. In this study, special constrained plate castings with progressive changes in cross-section were designed, which enabled progressive solidification. The hot tearing behavior of a newly developed NZ30K Mg alloy (Mg-3.0Nd-0.2Zn-Zr, wt.%) was studied under progressive solidification using various mold temperature distributions and constraint lengths. Of these, a homogeneous mold temperature distribution is found to be the best option to avoid hot tearing, followed by a local low mold temperature distribution (with a chiller), then a gradient mold temperature distribution. Unexpectedly, compared with the homogeneous mold temperature distribution, adding a chiller does not provide any further reduction in the hot tearing susceptibility of the NZ30K Mg alloy. A high mold temperature and a short constraint length increase the hot tearing resistance of cast Mg alloys. Progressive solidification is not a sufficient and necessary condition to avoid the formation of hot tearing. The two key factors that determine the occurrence of hot tearing under progressive solidification are the maximum cooling rate and the constraint length. Decreasing these values can reduce the incidence of hot tearing.

No-bake resin-bonded sand is commonly used in casting production. However, its air pollution is relatively serious, especially in the molding and pouring process. For this reason, it is necessary to study the gas evolution characteristics of no-bake resin-bonded sand from room temperature to high temperatures, and not only the amount of gaseous products, but also the composition of the gaseous products. No-bake furan resin-bonded sand (#1), phenolic urethane no-bake resin-bonded sand (#2), and alkaline phenolic no-bake resin-bonded sand (#3) are the three most common no-bake resin-bonded sands in casting. The gas evolution volume and rate of these three no-bake resin-bonded sands were studied. Thermogravimetry-mass spectrometer (TG-MS), headspace-gas chromatography/mass spectrometer (HS-GC/MS), and pyrolysis-gas chromatography/mass spectrometer (PY-GC/MS) were used to measure the composition of the gaseous products emitted from binders at room temperature and high temperatures. The differences between formaldehyde, heterocyclic aromatic compounds (HAC), monocyclic aromatic hydrocarbons (MAH), and polycyclic aromatic hydrocarbons (PAHs) gaseous products from the three types of no-bake resin-bonded sands during the molding and casting process were compared. From the perspective of environmental protection, alkaline phenolic no-bake resin-bonded sand and no-bake furan resin-bonded sand are better than phenolic urethane no-bake resin-bonded sand.

Central region coarse grains and centerline segregation are common defects in aluminum ingots fabricated by direct chill (DC) casting. A double cooling field was introduced into the DC casting process to reduce these defects, whereby the external cooling was supplied by the mold and water jets, and intercooling was achieved by inserting a rod of the same alloy into the molten pool along the central axis of the ingot. Rather than forming a good metallurgical interface during solid-liquid compound casting, in the present work, the purpose of inserting the rod is to enforce internal cooling and consequently decrease the sump depth. Moreover, the insertion provides more nucleation sites with the unmolten á-Al particles. The structure and the macrosegregation of 2024 Al alloy ingots prepared by DC casting with and without the inserts were investigated. Results show that when the inserting position is 50 mm above the upper edge of the graphite ring, significant grain refinement in the central region of the ingot and a reduced centerline segregation are achieved.

针对RV（rotate vector）减速器在工作过程中存在的零件磨损导致传动精度下降的问题，建立了考虑摆线轮磨损的RV减速器传动精度动态可靠性模型，进行传动精度可靠性分析，并对关键零件的公差以及摆线轮的修形参数进行优化设计。以某重载RV减速器为研究对象，利用Archard磨损公式对摆线轮的磨损深度进行计算，分析轮齿齿廓磨损的分布情况，并基于数值仿真数据利用高斯过程回归模型预测磨损量；建立了含动态磨损的RV减速器传动精度可靠性模型，用蒙特卡洛法求解其动态可靠度；建立了以传动精度动态可靠度为约束条件，以加工成本最低、额定寿命周期内最大磨损量最小为优化目标的优化模型，采用多目标遗传算法求得最优解。结果表明；优化后摆线轮的磨损量略微增大，而减速器的加工成本明显降低；优化后减速器传动精度可靠度得到明显提高，在额定寿命6 000 h内的可靠度满足预期要求。研究结果可以为高精度RV减速器的设计提供参考。

Based on wire arc additive manufacturing (WAAM) technology, AZ31 magnesium alloy in bulk was successfully fabricated, and its microstructure as well as mechanical properties in different planes were observed and analyzed. The AZ31 magnesium alloy has a similar microstructure in the building direction (Z) and travel direction (X), both of which are equiaxed grains. There are heat-affected zones (HAZs) with coarse grains below the fusion line. The second phase is primarily composed of the Mg₁₇Al₁₂ phase, which is evenly distributed in different directions. In addition, the residual stress varies in different directions. There is no significant difference in the hardness of the AZ31 alloy along the Z and X directions, with the average hardness being 68.4 HV and 67.9 HV, respectively. Even though the specimens' ultimate tensile strength along the travel direction is higher in comparison to that along the building direction, their differences in elongation and yield strength are smaller, indicating that the anisotropy of the mechanical properties of the material is small.

Laser directed energy deposition (DED) is a multi-physics process that accompanies mass flow, energy transfer, and complex phase transitions. The printing characteristics of small size parts are significantly affected by the progressive variations of the temperature fields and the fluid flow within the molten pool. In this work, the deposition characteristics during multi-layer and multi-track laser DED were explored through a well-tested phenomenological model and corresponding experimental results. The variations of the build profiles and the decoupled track and layer profiles were systematically examined. Moreover, the printing characteristics of the builds with different scanning lengths were compared. Results showed that the multi-layer and multi-track transient deposition processes generated a significantly wavy surface profile. Compared with the long scanning length part, the beginning region of the short build produced an obvious bulge followed by sharply decreased height along the scanning direction. The transverse section of the short build varied significantly at different positions. Two adjacent columns of tracks were extracted from the overall build, demonstrating that the tracks tilted outwards and the angle increases along the scanning direction. The 3D numerical model was validated with corresponding experiments for builds with various layers. The scientific findings from this work can provide useful insights for the understanding of the additive mechanisms during laser DED for the precise shape control of small size parts.

A novel α+β titanium alloy with multi-alloying addition was designed based on the cluster formula 12[Al-Ti₁₂](AlTi₂)+5[Al-Ti₁₄](AlV_1.2Mo_0.6Nb_0.2) which was derived from Ti-6Al-4V.The nominal composition of this novel alloy was determined as Ti-6.83Al-2.28V-2.14Mo-0.69Nb-6.79Zr.In this study,the novel alloy and Ti-6Al-4V alloy samples were prepared by laser additive manufacturing.The microstructure,micro-hardness,room/high temperature tensile properties of the as-deposited samples were investigated.Compared to Ti-6Al-4V,the novel alloy has much higher room and high temperature (600℃) tensile strengths,which are 1,427.5 MPa and 642.2 MPa,respectively;however,it has a much lower elongation (3.2%) at room temperature because of the finer microstructure.To improve the elongation of the novel alloy,heat treatment was used.After solution at 960℃ or 970℃ for 1 h followed by air cooling and aging at 550℃ for 4 h followed by air cooling,a unique bi-modal microstructure which contains crab-like primary α and residual β phase is obtained,improving the compression elongation by 80.9% compared to the as-deposited samples.The novel alloy can be used as a high-temperature and high-strength candidate for laser additive manufacturing.