Comparison of microstructures and mechanical properties of composite extruded AZ31 sheets

The microstructures and mechanical properties of the composite extruded AZ31/AZ31 and AZ31/4047 Al sheets were investigated and made a comparison to the conventional extruded AZ31 sheet.Owing to the introduced intense shear deformation at the interface during the composite extrusion,grain refinement and tilted texture were detected in AZ31 layers of the AZ31/AZ31 and AZ31/4047 Al sheets,while the conventional extruded AZ31 sheet exhibited a relative coarse,inhomogeneous microstructure and strong basal texture.The compressiontension yield ratio was increased gradually from the AZ31 to the AZ31/AZ31 and AZ31/4047 Al sheets.Besides,the AZ31/4047 Al sheet could successfully accomplish the whole bending forming process at room temperature,while the AZ31 and AZ31/AZ31 sheets were both bend-formed to failure with significant cracks in the outer tensile region under the identical bending parameters.Moreover,under the same bending strain,both the outward offset degree of strain neutral layer and the sheet thickening were more serious in the AZ31/4047 Al composite sheet than those of the AZ31 and AZ31/AZ31 sheets.The foremost reason was the quite wide gap of material properties between Mg alloy AZ31 layer(tensile loading in the outer region)and Al 4047 layer(compressive loading in the inner region).

Influence of minor Ce additions on the microstructure and mechanical properties of Mg-1.0Sn-0.6Ca alloy

The microstructure and mechanical properties of Mg-Sn-Ca-Ce alloys with different Ce contents(0.0,0.2,0.5,1.0 wt%)were studied at room temperature.Ce additions to ternary Mg-Sn-Ca alloy resulted in grain refinement as well as a change in the category of second phase from CaMgSn to(Ca,Ce)Mg Sn and Mg12Ce.The volume fraction of second phase increased with rising Ce content,which aggravated the restriction of DRXed grain growth during the extrusion process and eventually led to texture weakening of as-extruded Mg-Sn-Ca based alloys.In terms of plasticity,owing to vigorously activated basal slip and homogeneous distributed tensile strain in tension,the tensile ductility of as-extruded alloys reached the maximum value of 27.6%after adding 0.2 wt%Ce,which enhanced by about 26%than that of ternary MgSn-Ca alloy.However,further Ce additions(0.5 and 1.0 wt%)would coarsen the second phase particles and then impair ductility.The tension-compression yield asymmetry of as-extruded Mg-Sn-Ca ternary alloy was alleviated greatly via Ce additions,due to the joint effects of grain refinement,increased amount of strip distributed second phase particles and texture weakening.

Unveiling annealing texture formation and static recrystallization kinetics of hot-rolled Mg-Al-Zn-Mn-Ca alloy

The development of Mg-Al-Zn-Mn-Ca series alloys provides a potential prospect to achieve high strength and formability at room temperature(RT).The formation of elliptical annular texture is treated as a crucial factor for the enhanced RT formability.However,the origin of such an elliptical annular texture formation has been rarely reported.Herein,we unveiled the formation and evolution of elliptical annular texture in the hot-rolled Mg-1.6 Al-0.8 Zn-0.4 Mn-0.5 Ca(AZMX1100,wt.%)alloy after annealing at different temperatures for 1 h,and its static recrystallization(SRX)kinetics in given annealing temperature for different time.The results revealed that the formation of elliptical annular texture in the hot-rolled AZMX1100 alloy after annealing was derived from nucleation-oriented SRX mechanism,which took place in 200-300°C,induced by cracked chain-shaped Al2 Ca phases,contraction twins,intersections of double twins,intersections of double twins and grain boundaries and non-basal slips.On further annealing from300-450°C,the grains with 45°–70°transverse direction(TD)preferentially grew,which made elliptical annular texture extended along the TD.Based on the Johnson-Mehl-Avrami-Kolmogorov(JMAK)model,Avrami exponent n value was estimated to be 0.68–1.02,attributed to non-random SRX nucleation,giving rise to the lower activation energy QRof nucleation of^74.24 k J/mol.Since the co-segregation of Al,Zn and Ca atoms in grain boundaries created a strong interaction of solutes and grain boundaries,the hot-rolled AZMX1100 alloy exhibited the higher activation energy Qg(~115.48 k J/mol)of grain growth.