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).

The effects of orientation control via tension-compression on microstructural evolution and mechanical behavior of AZ31 Mg alloy sheet

The grain orientation control via twinning activity on deformation features is of great significance to offer a key insight into understanding the deformation mechanism of Mg alloy sheets.The{10–12}twinning were performed by pre-strain paths,i.e.,tension(6%)and compression(5%)perpendicular to the c-axis along extrusion direction(ED),to investigate the microstructural evolution and mechanical properties of AZ31 Mg alloy sheets.The distinction in the texture evolution and strain hardening behavior was illustrated in connection with the pre-strain paths for the activities of twinning and slip.The result shows that the activation of the deformation mode was closely bound up with the grain orientation and the additional applied load direction.The{10–12}twin-texture components with c-axis//ED were generated by precompression,which can provide an appropriate alternative to accommodate the thin sheet thickness strain and enhance the room temperature formability of Mg alloy sheet.

Enhanced mechanical properties of Mg-3Al-1Zn alloy sheets through slope extrusion

A novel extrusion approach,entitled slope extrusion(SE),was employed to manufacture AZ31(Mg-3Al-1 Zn,wt%)alloy sheets.The microstructures,textures,and mechanical properties were investigated,compared with those of the AZ31 sheet fabricated by conventional extrusion(CE).Through the combination of finite element simulation and actual experiment,the ultimate results indicated that significant grain refinement(from 9.1 to 7.7 and 5.6μm)and strong basal texture(from 12.6 to 17.6 and 19.5 mrd)were achieved by the SE process.The essence was associated with the additional introduced inclined interface in the process of SE,which could bring about more asymmetric deformation and stronger accumulated strain along the ND when compared with the process of CE.As a consequence,the SE sheets exhibited a higher yield strength(YS)and ultimate tensile strength(UTS)than the counterparts of the CE sheet,which was mainly assigned to the synergistic effects from grain refining and texture strengthening.

Improving the room-temperature bendability of Mg-3Al-1Zn alloy sheet by introducing a bimodal microstructure and the texture re-orientation

A significant enhancement of bendability was achieved by the introduction of bimodal microstructure for AZ31B alloy sheets via pre-compression and subsequent annealing(PCA)process.This combined treatment led to the c-axis of the extracted samples that were inclined by 30°to the rolling direction(30°sample)further shifting toward the rolling direction(RD)and resulting in a higher Schmid factor(SF)value of basal slip under the RD tensile stress.Furthermore,the bimodal microstructure that was introduced by the PCA process broke the damage bands(DBs)in the initial hot rolled AZ31B alloy sheets and gave rise to a more uniform strain distribution in the outer tension region of the bending samples,in which the tensile deformation was accommodated by the equally distributed{101^(-)2}tension twinning and basal slip.Consequently,the bimodal microstructure,shifted basal texture and the modification of DBs were responsible for the significant enhancement in the bendability of the AZ31 alloys.

Effects of Li addition on the microstructure and tensile properties of the extruded Mg-1Zn-xLi alloy

Li addition is verified to be an effective method to increase the room temperature ductility and formability of Mg alloys.In the present study,the microstructure,texture,and tensile properties of the extruded Mg-1Zn-xLi(wt%,x=0,1,3,5)alloy sheets were studied by X-ray diffraction(XRD),scanning electron microscope(SEM),and electron backscatter diffraction(EBSD).It was found that Li addition resulted in the grain coarsening and the development of new transverse direction(TD)-tilting and{101^(-)0}parallel to extrusion direction textures,which was related to the improved dynamic recrystallization and the increased prismatic slip during extrusion.The Mg-1 Zn-5 Li sheet showed the weakest texture,which contained both basal and TD-tilting oriented grains.No additional phase was formed with Li addition.The yield strength of Mg-1Zn-xLi sheets gradually decreased with increasing Li content,which was mainly related to the grain coarsening and texture weakening.In addition,the ductility of the Mg-1Zn-xLi sheet was remarkably enhanced by Li addition.The elongation of the Mg-1 Zn-5 Li sheet was 30.3%along the TD,which was three times than that of Mg-1 Zn sheet.Microstructural analysis implied that this significant ductility enhancement was associated with the improvement activation of prismatic and basal slips during the tensile tests.This study may provide insights into the development of high-ductility,low-density Mg-Zn-Li based alloys.

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.

In-situ investigation on the microstructure evolution of Mg-2Gd alloys during the V-bending tests

In this work,the in-situ observation of the microstructure in the Mg-2Gd(wt%)alloys during V-bending tests was operated.The microstructure and texture evolutions were characterized by the in-situ electron backscatter diffraction(EBSD),scanning electron microscopy(SEM)and the high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)technique.The results revealed a unique microcracks nucleation mechanism in the Mg-Gd alloys compared with the traditional Mg alloy(AZ31 alloy).The microcrack was nucleated at the grain boundary for the Mg-2Gd alloy and in the intragranular for the AZ31 alloy during the bending process.This difference mode between the Mg-Gd and the AZ31 alloys was mainly attributed to the more random topology of the grain boundary network,the lower grain boundary cohesion and the enhanced hinder ability for the dislocations due to the segregated Gd atoms in the Mg-Gd alloy.Furthermore,the microcracks that had a large angleθwith the extruded direction(ED)in the Mg-Gd alloys were preferred nucleated since grain boundaries had the larger normal stress during the bending process.