Enhanced strength-ductility synergy and mechanisms of heterostructured Ti6Al4V-Cu alloys produced by laser powder bed fusion
School of Engineering / Centre for Advanced Materials and Manufacturing
National Natural Science Foundation of China / Project of MOE Key Lab of Disaster Forecast and Control in Engineering in Jinan University / Guangzhou Basic and Applied Basic Research Foundation / Guang- dong Province Basic and Applied Basic Research Foundation / Guangxi Key Laboratory of Information Materials / Open Project Program of the State Key Laboratory of Mechanical Transmissions in Chongqing University / Fundamental Research Funds for the Central Universities
Limited slip systems of structure always play a major role in hindering strength-ductility synergy improvement of titanium (Ti) alloys. To overcome the strength-ductility trade-off of Ti alloys, heterostructure is introduced into Ti6Al4V-xCu (x = 0, 1, 3, 5 wt.%) alloys produced by laser powder bed fusion (LPBF), and the formation mechanism and deformation behavior of heterostructures were investigated. The results showed that the monolithic ' in the LPBF-produced Ti6Al4V-xCu (wt%) alloys is decomposed into dual and " after heat treatment at 600–900 °C through ' + Ti2Cu matastable phase + ". The multistage transformation of ' to and " is driven by thermal activation (temperature > 800 °C), Cu addition and rapid cooling of water quenching. The heterostructure with and " in the LPBF-produced Ti6Al4V-5Cu alloy after heat treatment at 800 °C results in high tensile strength (∼1.3 GPa) and large elongation (∼15%). The enhanced strength-ductility synergy is attributed to the decomposition of brittle ' and Ti2Cu, as well the soft-hard heterostructure of " and . Moreover, the deformation twins (DTs) in " and the heterogeneous interfaces of and " can also improve the strength and ductility of the LPBF-produced Ti6Al4V-xCu alloys. These findings elucidate the influence of heterostructure ( and ") on strength and ductility, which is helpful for designing Ti alloys with excellent mechanical properties.