Improved fatigue endurance ratio of additive manufactured Ti-6Al-4V lattice by hot isostatic pressing

Publication date: 15 November 2017
Source:Materials & Design, Volume 134
Author(s): Ming-Wei Wu, Jhewn-Kuang Chen, Bo-Huan Lin, Po-Hsing Chiang
Selective laser melting (SLM) is a dominant additive manufacturing (AM) method of fabricating various porous and high-density metallic materials with complex geometries. However, the SLM porous materials generally exhibit inferior fatigue performances, particularly the endurance ratio. The main purpose of this study was thus to investigate the influence of hot isostatic pressing (HIP) on the fatigue property of SLM Ti-6Al-4V lattice with a self-designed unit cell. The results show that HIP treatment at 1000°C/150MPa can eliminate the pore in the strut and respectively decreases the microhardness from 403HV to 324HV and the yield strength from 143MPa to 100MPa. Furthermore, the fatigue strength and the endurance ratio at 10⁶cycles are increased after HIP. The HIP process sufficiently improves the fatigue endurance ratio at 10⁶cycles of SLM lattice from 0.3 to 0.55, which is comparable to that of the solid metallic material. This improvement can be predominantly attributed to the phase transformation from brittle α′-martensite to tough α+β mixed phases after HIP. The tougher α+β mixture can help resist the propagation of fatigue cracks by crack blunting and thus improve the fatigue properties.

Graphical abstract

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