Integrated manufacturing of powder metallurgy preparation-thixoforming for Al_0.8Co_0.5Cr_1.5CuFeNi HEA: Excellent formability and enhancement by in-situ generated Al₂O₃ in liquid phase

Thixoforming displays wild application prospects in manufacturing Cu containing high entropy alloy (HEA) product. In current work, we proposed a novel manufacturing strategy on powder metallurgy preparation-thixoforming for Cu containing HEAs, integrating material preparation, shaping and strengthening objectives. During thixoforming, oxide in-situ generation in liquid phase was utilized to reinforce soft phase, achieving the strengthening of component. Based on this strategy, manufacturing of disc-shaped component for a model Al_0.8Co_0.5Cr_1.5CuFeNi HEA was studied. Compared to 1175 °C thixoforming, room-temperature strength experiences a breakthrough increase at 1200 °C and 1225 °C, accompanied by an increase in yield strength of 323.8 MPa and 314.8 MPa, an increase in ultimate strength of 374.2 MPa and 470.0 MPa, meanwhile, fracture strain improves, which is caused by a considerable amount of in-suit generated Al₂O₃. Homogeneous and almost defect free microstructure obtained under higher temperature conditions ensures uniformity of mechanical properties for the whole component. As thixoforming temperature increases, preferred orientation of grain fiber shape becomes random, plastic deformation of solid grain (PDS) turns to flow of liquid incorporating solid particles (FLS), sliding between solid particles (SS) during material flow filling, which effectively reduces material damage risk caused by strain localization. In-situ generated Al₂O₃ in liquid phase helps to hinder crack propagation and blunt crack tip in Cu rich soft phase. Al₂O₃ only strengthens soft phase, relieving mismatch of strength-plasticity properties between soft and hard phase, accordingly, failure of soft phase is delayed and simultaneous improvement of strength and plasticity is achieved.