Effect of External Pressure on the Microstructure and Mechanical Properties of In Situ (ZrB2+Al2O3/Al3Zr)/6016 Nanocomposites

In this study, effect of external pressure on the microstructure and mechanical properties of in situ (ZrB2+Al2O3/Al3Zr)/6016 composites, synthesized under electromagnetic field, is investigated using scanning electron microscopy, X-ray diffraction and tensile testing. It is found that the application of 0.5MPa external pressure can promote uniformity in shape and slight decrease in alpha-Al grain size due to pressure-assisted faster solidification rate, and thus results in strengthening of both the 6016 alloy and in situ (ZrB2+Al2O3/Al3Zr)/6016 nanocomposite. It is also found that the external pressure can inhibit the growth of in situ reinforcement particles present in (ZrB2+Al2O3/Al3Zr)/6016 nanocomposite, restricting their size to lower aspect ratios. The improved strengthening of the composite matrix contributes to the simultaneously higher yield strength (YS), ultimate tensile strength (UTS), %elongation and hardness. The work hardening rate and improvement in mechanical properties are discussed in terms of reinforcement particles' size and morphology of tensile fracture.