Cryogenic high-speed rolling (CHSR), where the sheet cooled in liquid nitrogen is supplied to rolls rotating at 1500 m/min at room temperature, was applied to several Cu alloys. After the CHSR, mechanical strength was improved with texture transition from the ‘copper-type’ to the ‘brass-type’ components. This trend was clearly observed in the case of Cu alloys with intermediate SFE. It is considered that the deformation mode changed from the dislocation slip to deformation twinning and shear banding under high Z parameter conditions of CHSR. It is also found that CHSR can improve the strength of Cu alloys with less decrease in electrical conductivity.
Recently, it was reported that Cu-Al alloys of low stacking fault energy (SFE) processed by severe plastic deformation show excellent tensile properties due to TWIP (Twinning induced Plasticity) phenomenon. In this study, Cu-15at% Al sheets were heavily processed by conventional multi-pass cold rolling up to 90% in reduction in thickness without annealing. In order to reveal the change in mechanical properties and the microstructure evolution, tensile test, hardness test, optical microscopy (OM) and electron backscattering diffraction (EBSD) analysis were performed. Deformation twinning due to low SFE is observed even in the case of low reduction in thickness. As the reduction increases, grains are refined by intersections of shear bands. It is found that the balance of strength and elongation of the processed sheets is comparable to those by severe plastic deformation followed by annealing in literature.
The mechanical properties and textures of 75% hot unidirectionally rolled and cross rolled commercial magnesium die-casting alloy AZ91D sheets were investigated for the different rolling temperatures 623K and 673K, respectively. As for mechanical properties, tensile testing results show total elongations of both as-unidirectional and as-cross-rolled sheets are enhanced by the repetition of rolling passes and inter-pass heating. The planar anisotropy of tensile strengths and elongations of cross-rolled at 673K are the smallest among the rolling conditions employed in the present study. Annealed sheets demonstrate the significant elongation to failure due to the static recrystallisation at 623K. Macro textures of the as-unidirectional-rolled sheets show typical double-peak (0001) basal textures with inclined peaks towards ±15° in RD. Contrastingly, macro textures of the as-cross-rolled sheets show the significant (0001) basal textures having double peaks at ±10° in TD and concentrically broader orientation distribution in RD and TD.
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