Effect of SiC Nanofiber Addition on Microstructure, Mechanical Properties and Creep Behaviour of High Pressure Die Cast AZ91-1Sr Alloy

Effects of nanofiber SiC (0.5 and 1 vol%) addition on microstructure, mechanical properties and creep behaviour of cold chamber high pressure die casting AZ91-1Sr alloy have been investigated. Experimental results indicate that the AZ91-1Sr alloy contains of α-Mg, β-Mg₁₇Al₁₂ and Al₄Sr intermetallic phases. With addition of nanofiber SiC, the Al₄C₃ and SiC peaks were detected. Also, the mechanical properties of the matrix alloy were improved. The AZ91-1Sr-1%SiC nanocomposite displays the best yield strength and hardness increment. Furthermore, the creep resistance of the matrix alloy was increased with increasing nanofiber SiC and the best creep resistance was obtained in the AZ91-1Sr-1SiC nanocomposite. The values of stress exponents and the activation energies for experimental specimen were found between 3.17–5.54 and 103.5–155.3 kJ/mol., respectively. When considered the results obtained from the values of stress exponents, the activation energies and SEM micrographs, it was thought that the dominant creep mechanism for the matrix alloy and nanocomposites is dislocation climb controlled.

Both of the nano-composites exhibited superior creep resistance compared to the matrix alloy under all the creep test conditions.