Investigation into the microstructure and dynamic compressive properties of selective laser melted Ti-6Al-4V alloy with different heating treatments

摘要

As a commonly used engineering material, the mechanical properties of titanium alloy under dynamic loads are closely related to their microstructure. In this work, the effects of solution treatment (ST) and solution and aging treatment (SAT) on the microstructure and dynamic compressive properties of Ti-6Al-4V alloy manufactured by selective laser melting were studied. The results showed that the microstructure of selective laser melted Ti-6Al-4V consisted of nearly full acicular a' martensite, then the acicular a' martensite was decomposed into α+β phase with basket-weave morphology with solution treatment. Clusters of α_2 particles with size of several hundred nanometers were precipitated in the a plates further with solution and aging treatment. The ultimate compressive strength (UCS) of selective laser melted TC4 alloy was increased with the increasing strain rate, showing strong strain rate hardening effect. Stress collapse happened once the strain exceeded 1500/s, which is the dominant failure model of selective laser melted TC4 under impacting load. As expected, the UCS of the ST sample decreased, but the ductility increased compared with the as-built sample; however, both the UCS and ductility of the SAT samples were enhanced synergistically due to the widely distributed α_2 precipitates. Besides, the SAT samples had the highest energy absorption compared with the as-built and ST counterparts under the same conditions, indicating that the SAT samples had better load-bearing capacities.