The Ti6Al4V parts produced by the existing selective laser melting (SLM) are mainly confronted with poor surface finish and inevitable interior defects, which substantially deteriorates the mechanical properties and performances of the parts. In this regard, ultrasonically-assisted machining (UAM) technique is commonly introduced to improve the machining quality due to its merits in increasing tool life and reducing cutting force. However, most of the previous studies focus on the performance of UAM with ultrasonic vibrations applied in the tangential and feed directions, whereas few of them on the impact of ultrasonic vibration along the vertical direction. In this study, the effects of feed rate on surface integrity in ultrasonically-assisted vertical milling (UAVM) of the Ti6Al4V alloy manufactured by SLM were systemically investigated compared with the conventional machining (CM) method. The results revealed that the milling forces in UAVM showed a lower amplitude than that in CM due to the intermittent cutting style. The surface roughness values of the parts produced by UAVM were generally greater than that by CM owing to the extra sinusoidal vibration textures induced by the milling cutter. Moreover, the extra vertical ultrasonic vibration in UAVM was beneficial to suppressing machining chatter. As feed rate increased, surface microhardness and thickness of the plastic deformation zone in CM raised due to more intensive plastic deformation, while these two material properties in UAVM were reduced owing to the mitigated impact effect by the high-frequency vibration of the milling cutter. Therefore, the improved surface microhardness and reduced thickness of the subsurface deformation layer in UAVM were ascribed to the vertical high-frequency impact of the milling cutter in UAVM. In general, the results of this study provided an in-depth understanding in UAVM of Ti6Al4V parts manufactured by SLM.
[1] K S Al-Rubaie, S Melotti, A Rabelo, et al. Machinability of SLM-produced Ti6Al4V titanium alloy parts. Journal of Manufacturing Processes, 2020(57): 768-786.
[2] C Ni, L Zhu, Z Yang. Comparative investigation of tool wear mechanism and corresponding machined surface characterization in feed-direction ultrasonic vibration assisted milling of Ti–6Al–4V from dynamic view. Wear, 2019, 436-437: 203006.
[3] M K Thompson, G Moroni, T Vaneker, et al. Design for additive manufacturing: Trends, opportunities, considerations, and constraints. CIRP Annals, 2016, 65(2): 737-760.
[4] T D Ngo, A Kashani, G Imbalzano, et al. Additive manufacturing (3D printing): A review of materials, methods, applications and challenges. Composites Part B: Engineering, 2018, 143: 172-196.
[5] S A M Tofail, E P Koumoulos, A Bandyopadhyay, et al. Additive manufacturing: scientific and technological challenges, market uptake and opportunities. Materials Today, 2018, 21(1): 22-37.
[6] R Singh, J S Khamba. Investigation for ultrasonic machining of titanium and its alloys. Journal of Materials Processing Technology, 2007, 183(2): 363-367.
[7] C Ni, L Zhu, C Liu, et al. Analytical modeling of tool-workpiece contact rate and experimental study in ultrasonic vibration-assisted milling of Ti–6Al–4V. International Journal of Mechanical Sciences, 2018, 142-143: 97-111.
[8] X Liu, D Wu, J Zhang, et al. Analysis of surface texturing in radial ultrasonic vibration-assisted turning. Journal of Materials Processing Technology, 2019, 267: 186-195.
[9] E Shamoto, T Moriwaki. Study on elliptical vibration cutting. CIRP Annals, 1994, 43(1): 35-38.
[10] C Zhang, Y Song. Design and kinematic analysis of a novel decoupled 3D ultrasonic elliptical vibration assisted cutting mechanism. Ultrasonics, 2019, 95: 79-94.
[11] F Ning, W Cong, Ultrasonic vibration-assisted (UV-A) manufacturing processes: State of the art and future perspectives. Journal of Manufacturing Processes, 2020, 51: 174-190.
[12] L Xu, H Na, G Han. Machinablity improvement with ultrasonic vibration–assisted micro-milling. Advances in Mechanical Engineering, 2018, 10(12): 1–12.
[13] H Sui, X Zhang, D Zhang, et al. Feasibility study of high-speed ultrasonic vibration cutting titanium alloy. Journal of Materials Processing Technology, 2017, 247: 111-120.
[14] F H Cakir, S Gurgen, M A Sofuoglu, et al. Finite element modeling of ultrasonic assisted turning of Ti6Al4V alloy. Procedia - Social and Behavioral Sciences, 2015, 195: 2839-2848.
[15] C Nath, M Rahman. Effect of machining parameters in ultrasonic vibration cutting. International Journal of Machine Tools and Manufacture, 2008, 48(9): 965-974.
[16] M Zhang, D Zhang, D Geng, et al. Effects of tool vibration on surface integrity in rotary ultrasonic elliptical end milling of Ti–6Al–4V. Journal of Alloys and Compounds, 2020, 821: 153266.
[17] J Liu, X Jiang, X Han, et al. Effects of rotary ultrasonic elliptical machining for side milling on the surface integrity of Ti-6Al-4V. The International Journal of Advanced Manufacturing Technology, 2018, 101(5-8): 1451-1465.
[18] Z Yang, L Zhu, G Zhang, et al. Review of ultrasonic vibration-assisted machining in advanced materials. International Journal of Machine Tools and Manufacture, 2020, 156: 103594.
[19] Z Dong, F Zheng, X Zhu, et al. Characterization of material removal in ultrasonically assisted grinding of SiCp/Al with high volume fraction. The International Journal of Advanced Manufacturing Technology, 2017, 93(5): 2827-2839.
[20] W X Xu, L C Zhang. Ultrasonic vibration-assisted machining: principle, design and application. Advances in Manufacturing, 2015, 3(3): 173-192.
[21] L Zhu, C Ni, Z Yang, et al. Investigations of micro-textured surface generation mechanism and tribological properties in ultrasonic vibration-assisted milling of Ti–6Al–4V. Precision Engineering, 2019, 57: 229-243.
[22] T Moriwaki, E Shamoto. Ultrasonic elliptical vibration cutting. CIRP Annals, 1995, 44(1): 31-34.
[23] G Quintana, J Ciurana. Chatter in machining processes: A review. International Journal of Machine Tools and Manufacture, 2011, 51(5): 363-376.
[24] C Ma, J Ma, E Shamoto, et al. Analysis of regenerative chatter suppression with adding the ultrasonic elliptical vibration on the cutting tool. Precision Engineering, 2011, 35(2): 329-338.
[25] A Suárez, F Veiga, L N L de Lacalle, et al. Effects of ultrasonics-assisted face milling on surface integrity and fatigue life of Ni-Alloy 718. Journal of Materials Engineering and Performance, 2016, 25(11): 5076-5086.
[26] X Li, P Zhao, Y Niu, et al. Influence of finish milling parameters on machined surface integrity and fatigue behavior of Ti1023 workpiece. The International Journal of Advanced Manufacturing Technology, 2017, 91(1): 1297-1307.
[27] M Cheng, D Zhang, H Chen, et al. Development of ultrasonic thread root rolling technology for prolonging the fatigue performance of high strength thread. Journal of Materials Processing Technology, 2014, 214(11): 2395-2401.
[28] J Sun, Y B Guo. A comprehensive experimental study on surface integrity by end milling Ti–6Al–4V. Journal of Materials Processing Technology, 2009, 209(8): 4036-4042.
[29] G Ongtrakulkij, A Khantachawana, K Kondoh. Effects of media parameters on enhance ability of hardness and residual stress of Ti6Al4V by fine shot peening. Surfaces and Interfaces, 2020, 18: 100424.
[30] Q Lin, H Liu, C Zhu, et al. Investigation on the effect of shot peening coverage on the surface integrity. Applied Surface Science, 2019, 489: 66-72.
[31] N Ferreira, J S Jesus, J A M Ferreira, et al. Effect of bead characteristics on the fatigue life of shot peened Al 7475-T7351 specimens. International Journal of Fatigue, 2020, 134: 105521.
