Effects of sintering temperature on microstructure and mechanical properties of Al-Ni-Sc-Zr alloy fabricated by powder metallurgy

Spark plasma sintering (SPS), followed by hot extrusion technique is an effective powder metallurgy strategy for preparing high-performance Al-Ni based alloys by forming large numbers of Al-Ni phases. In order to obtain optimum strength and plasticity, one feasible method is to control the size and shape of Al-Ni phases by changing the sintering temperature of SPS. Thus, this study investigates the impact of SPS temperature on the microstructure and mechanical properties of Al-Ni-Sc-Zr alloy. The results indicate that the strength decreases gradually while the plasticity gradually increases with rising SPS temperature. The decrease in strength is mainly due to the coarsening of Al-Ni phases, resulting in the reduced particle strengthening. While, this coarsening transforms the shape of Al-Ni phases from rod-shape to spherical-shape, thus eliminates the strain heterogeneity around the Al-Ni phases during deformation. Additionally, a higher SPS temperature suppresses the appearance of Ni-free region, further mitigating the heterogeneous distribution of plasticity during deformation. These combined effects alleviate strain localization and microcracks initiation, thereby promoting the plasticity. These results highlight the significant role of SPS temperature in strength and plasticity, which should be considered carefully for preparing high-performance eutectic Al alloys processed by powder metallurgy.