Effect of particle size ratio on microstructure and mechanical properties of aluminum matrix composites reinforced with Zr48Cu36Ag8Al8 metallic glass particles

Aluminum matrix composites reinforced with Zr48Cu36Ag8Al8 glassy particles were synthesized by powder metallurgy using reinforcement particles larger than the matrix. The effect of the matrix to reinforcement particle size ratio (PSR) on the microstructure and mechanical properties was studied. The results show that high densification (relative density > 98%) was achieved and the glassy particles retained the amorphous structure in all the composites. Quantitative particle distribution analysis in the three-dimensional space indicated that the homogeneity distribution index decreases with reducing PSR. The findings suggest that a ratio of 1/3 <= PSR <= 1 can be used to obtain composites with rather homogenous distribution of the reinforcement particles. Both compressive and tensile yield strengths of the composites are not sensitive to the PSR change (in the range of 1/3-1/6), whereas the ultimate tensile strength and the ductility are significantly reduced with decreasing PSR; this behavior is accompanied by the change of the fracture mode. The experimental yield strength was found to be consistent with the quantitative strengthening mechanism calculations, and indicated that the reduced matrix ligament size, the thermal mismatch and load bearing are the main strengthening contributions.