Deformation Behavior And Mechanical Performance Of SiC Nanoparticles Reinforced AZ31 Magnesium Matrix Nanocomposite During Hot Rolling

The SiC nanopartic les reinforced AZ31 magnesium matrix nanocomposites were subjected to hot rolling in the present work,after which the O M,SEM,TEM,EBSD and XRD were applied for the analysis of microstructure and texture evolut ion,accompanied by the tensile test along rolling direction(RD)and transverse direction(TD).Based on the systemic analys is,the effects of SiC nanoparticles on the microstructure,texture and mechanical properties of AZ31 alloy were revealed.In addit ion,the magnesium matrix nanocomposites were subjected to rolling at different temperatures,inc lud ing 300?C,350?C and 400?C.And the effects of temperature on the rolling behavior of nanocomposite were clarified.Finally,hot rolling was performed on nanocomposite extrusion sheet,and then followed by hot rolling.The evolut ion of microstructure,texture and mechanical properties of extruded sheet during rolling was studied.The homogenized AZ31 alloy and SiCnp/AZ31 nanocomposite had coarse microstructure.During rolling,the microstructure was refined by progressive dynamic recrystallization(DRX),which was enhanced continuous ly wit h the increase of rolling reduction.For the AZ31 alloy,shear bands were observed after 2-pass rolling,and with the increase of rolling passes,the amount of shear bands was increased obvious ly.However,in the nanocomposite,the appearance of shear bands was delayed and the amout of shear bands was much less than the rolled AZ31 alloy under the same rolling reduction,indicating t he inhibit ion of SiC nanopartic les on shear band formation.Furthermore,the SiC nanopartic les were redistributed as particle bands paralle l with the rolling direction after rolling deformat ion,which can stimulate the formation of local la mellar structure.This lame llar structure consisted of fine-grain region near nanoparticle bands and coarse-grain region far away from the nanoparticle bands.After init ial rolling,the typical basal texture was formed in both of the AZ31 alloy and the nanocomposite,which was due to the occurrence of extension twinning.With the increase of rolling reduction,the basal texture was overall enhanced.And the nanocomposite sheets showed higher basal texture intensit y than the AZ31 sheets with same rolling reduction,which was attributed to the inhibit ion of shear bands formation by the incorporated nanoparticles.Rolling can significantly promote the strength of AZ31 alloy and the nanocomposite,while the elongation was decreased.The comparison between the strengt h of rolled AZ31 alloy and nanocomposite showed that the addit ion of SiC nanopartic les can enhance the strength of the base al oy.Rolling temperature had obvious effect on the amount of twins and the DRX behavior of the nanocomposite.Wit h the increase of rolling te mperature,the amount of twins was decreased and the percentage of DRX was promoted.Under 300?C,the shear bands appeared after 2-pass rolling,while higher temperature of 350?C and 400?C delayed the shear bands to appear until 6-pass rolling,which ind icated the inhibit ion effect on the formation of shear bands.O n the other hand,the rolling temperature affected the formation process of shear bands,result ing in the different characterized shear bands.Addit ionally,the promotion of temperature can modify the distribut ion of SiC nanopartic les.Meanwhile,the rolling temperature had significant influence on texture intens ity of the nanocomposite sheets.The nanocomposite sheets rolled at 350?C had the strongest basal texture and the ones rolled at 300?C had the weakest.The basal texture variation w ith rolling temperature was ma inly due to the variation of compression/double twins and the associated DRX fraction wit h the temperature.Yield strengt h of the nanocomposite was enhanced after 4-pass rolling at different temperatures,while the elongat ion decreased.With increase of the rolling passes,the yield strength increased slight ly,while the elongation increased first and then decreased.For the sheets with same rolling reduction,the yie ld strength decreased and the elongation increased with increase of the temperature.With proceeding of the rolling process,microstructure of the extruded nanocomposite sheet became unifor m gradually t ill 4 passes,fo llow ing which the shear bands started to form,making the microstructure heterogeneous.However,during the whole direct rolling process of the homogenized nanocomposite,the microstructure showed non-uniformity.The yield strength of the extruded nanocomposite was improved by 4-passes rolling,while the elongat ion increased along RD and decreased along TD.The yield strength decreased along RD and increased slight ly along TD with successive rolling,and the elongation decresed along both RD and TD.Comparison of the yield strength between the 4P sheet from the extruded nanocomposite and the 11 P sheet from the homogenized nanocomposite,the former showed comparable strength w ith the later while w ith much better elongation.The difference between the elongat ions was ascribed to the difference of the uniformity of their microstructure.Results showed that pre-extrusion combined with the subsequent hot rolling can benefit to obtaining superior strength and plasticity.