Microstructure and mechanical properties of caliber rolled AlN/AZ91 composite

Abstract

The multi-pass caliber rolling was applied to in-situ AlN/AZ91 composite rods, and the yield strength of 295.3 MPa, ultimate tensile strength of 384.7 MPa, fracture elongation of 12.3% and a good surface morphology were obtained under the reduction ratio of 78%. The results showed that the grains of the caliber rolled AlN/AZ91 composite rods were remarkably refined due to the occurrence of dynamic recrystallization (DRX), while the in-situ AlN reinforcements induced the nucleation of {101‾2} extension twins, and preferentially promoted the formation of extension twin-induced DRX before discontinuous DRX. Especially, twinning-induced DRX weakened the texture more effectively compared with discontinuous DRX. In addition, it was also found that the increased yield strength was mainly attributed to solid solution atoms, twinning-induced DRX, discontinuous DRX, high density dislocations and nano-sized γ-Mg17Al12 precipitates in the in-situ AlN/AZ91 composite rods, while the high ductility was mainly ascribed to grain size refinement, weakened texture and the activation of non-basal slip systems at room temperature.