Effect of sintering temperature on the microstructure and mechanical properties of Fe-30%Ni alloys produced by spark plasma sintering

Fe-30%Ni alloys were produced by sintering in the hybrid hot press spark plasma sintering system using iron and nickel as raw materials. The results indicate that the relative density, microhardness and fracture morphology depend on the sintering temperature which also affects the microstructure. The densification and grain size of the alloys increased with increasing sintering temperature, facilitating necking of grains. In the case of the sintering temperature at 1230°C, a relative density of 98.7% and a maximum grain size of around 200 μm were obtained, and the maximum microhardness of 284Hv1.0, and the microhardness indentations revealed pincushioning indicating better sintering. Microhardness indentations at 1100°C and below were characterized by barreling, indicating poor densification and/or microhardness. The fracture type changing from intergranular fracture to transgranular fracture is an indication of improved consolidation of the Fe-30%Ni alloy with increasing sintering temperature.