Microstructure and mechanical properties of AA7075/Al3Ni composites produced by compocasting

The present study investigates the effects of the parameters of the compocasting method on the microstructure and mechanical properties of AA7075/Al3Ni composites. By applying compocasting in the semisolid-liquid condition, the Ni reinforcement was varied from 0 to 5 wt%. The results indicate that an increase in the weight percentage of nickel does not have a major impact on the alpha-Al grain size. However, the most significant changes were in the distribution coefficient and the porosity percentage of the composite. Moreover, the iron-rich contaminant with strip-like morphology increased in the composites due to the increase in the stirring time by increasing the weight percentage of nickel. Compared to the reinforcement-free matrix, the hardness, strength, and toughness of the composite fabricated under optimal conditions increased by 37%, 49%, and 100%, respectively. The highest hardness, tensile strength, and toughness values were achieved using 3 wt% of Ni reinforcement, a stirring temperature of 530 degrees C, and a stirring speed of 450 rpm. The eutectic structure in the microstructure of the composite acted as a crack nucleation site, and the expansion of this structure resulted in lower strength and toughness in the composites.