Microstructure evolution and tensile property of high entropy alloy particle reinforced 316 L stainless steel matrix composites fabricated by laser powder bed fusion

Abstract

316 L stainless steel is prone to failure under high-strength conditions due to low strength and poor wear resistance, which limits its further application severely. In this study, 2 wt% FeCoNiAlTi high entropy alloy (HEA) powders and 316 L stainless steel powders were mixed to fabricate HEA reinforced 316 L stainless steel matrix composites (MMCs) via laser powder bed fusion (LPBF). The influence of scanning speed on microstructure evolution, the mechanical properties and the strengthening mechanisms have been investigated systematically. The LPBF-fabricated HEA/316 L MMCs consists of both γ-Fe and α-Fe phases. For HEA/316 L MMCs, the grains are refined with the increase of scanning speed and the minimum size is around 0.64 µm. The precipitation of nanoparticles is observed, and the nanoparticles form a strong interfacial bounding with matrix, which indicates the good metallurgical bonding between HEA and 316 L stainless steel. The tensile strength of the LPBF-fabricated composites increases from 1164 MPa to 1276 MPa with increased scanning speed, which is approximately twice as high as the strength of LPBF processed 316 L stainless steel matrix. The contribution of each strengthening mechanism is calculated, and the contribution of particle strengthening is the largest (from 241 MPa to 300 MPa, changing with scanning speed). This work demonstrates the feasibility of using HEA as potential reinforcement in metallic systems and can further enlarge the application field of metallic materials.