Rapid hardening response of ultra-hard Ti-6Al-2Sn-4Zr-6Mo alloy produced by laser powder bed fusion

Post heat treatment is essential for additively manufactured alloys to eliminate residual stress and in some cases further improve mechanical performance. This study systematically investigated the hardening response of a Ti-6Al-2Sn-4Zr-6Mo alloy processed by laser powder bed fusion (LPBF) to a one-step heat treatment. The results revealed significant hardening at both 500 degrees C and 650 degrees C. Most notably, an ultra-high peak-hardness of 563VHN was achieved within 5 mins of heat treatment at 650 degrees C due to a unique martensite-decomposed alpha+beta micro-structure consisting of alternating long beta laths that are-5 nm thick and alpha laths that are-35 nm thick, and within the alpha laths are also short beta laths that are-2 nm thick with an-11 nm inter-spacing. The influence of both types of beta laths on the alpha lath thickness was established and related to the ultra-high hardness observed, which provides new insight for the design of new metastable LPBF-processed Ti alloys.

Automated summary

Post heat treatment is essential for additively manufactured alloys. This study investigated the hardening response of a Ti-6Al-2Sn-4Zr-6Mo alloy processed by laser powder bed fusion (LPBF) to a one-step heat treatment. The results revealed significant hardening at both 500 degrees C and 650 degrees C. The unique microstructure consisting of alternating long beta laths and short alpha laths, along with the influence of both types of laths on the alpha lath thickness, provides new insight for the design of new LPBF-processed Ti alloys.