Selective laser melting processing of heterostructured Ti6Al4V/FeCoNiCrMo alloy with superior strength and ductility

Abstract

In the selective laser melting (SLM) process, the transient nature of the molten pool and rapid cooling rate facilitates partial homogenization of components, resulting in attaining a finer scale concentration modulation and spatial heterostructure. However, the SLM-processed Ti6Al4V alloys have long suffered from the problem of both large detrimental columnar grains and poor work-hardening capacity. In this study, a high entropy alloy of FeCoNiCrMo particles was incorporated into the Ti6Al4V alloy and fabricated by the SLM technique. The resulting alloys exhibited a fine-scale modulated β + α' spatial heterostructure, delivering a notable tensile strength of 1366.4 MPa and a uniform elongation of approximately 8.7% with an excellent work-hardening capacity exceeding 300 MPa. This outstanding performance can be attributed to the progressive transformation-induced plasticity (TRIP) effect and hetero-deformation induced (HDI) strengthening within the ultra-refined α' martensite and metastable β phase regions. This work provided a compelling model of additive manufacture of heterogeneous structures while offering new insights and directions for the development of metallic materials with high strength-ductility characteristics.