Effect Of SiC_p On Dynamic Recrystallization And Precipitation Behavior Of Magnesium Alloy

Owing to the fine dynamic recrystallization(DRX)grains size and low DRXed ratio for Mg alloy deformed at low temperature,it is hard to achieve good matching between strength and plasticity.To overcome this problem,based on the idea that micron SiC_p can promote the DRX nucleation of Mg alloy,the formation mechanism of the particle deformation zone(PDZ)was studied.The microstructure evolution of Mg-5Zn alloy under the effect of micron SiC_p and PDZ size around SiC_pduring high temperature compression deformation was analyzed.The influence mechanism of SiC_p and PDZ size on DRX and dynamic precipitation behavior of Mg-5Zn alloy was clarified.Based on above research and analysis,the microstructure and mechanical properties of the micron SiC_p/Mg-5Zn after the extrusion deformation were studied.The effects of SiC_p,PDZ size and precipitates on the dislocations and grain boundaries were clarified,and the synergistic strengthening mechanism was revealed.The results show that the deformation mismatch between SiC_p and Mg-5Zn alloy results in the formation of PDZ with high dislocation density and large misorientation gradient around SiC_p during the compression deformation.PDZ can promote DRX nucleation,but which is related to the degree of deformation.PDZ promotes the DRX nucleation with the increase of deformation degree.However,the nucleation of DRXed grains is accelerated with the increase of PDZ size,when the deformation degree is the same.The addition of minor SiC_p can promote the precipitation of Mg-Zn phase in Mg-5Zn alloy.The main reasons are as follows:on the one hand,the PDZ around SiC_p itself is the distortion zone of high dislocation density,which can promote the atomic diffusion,it is conducive of the nucleation and growth of precipitated phase;on the other hand,SiC_ppromotes the nucleation of DRXed grains,which increases the DRX ratio in Mg-5Zn alloy.The DRX region contains a large number of grain boundaries,which not only reduces the interface energy and mismatch strain,but also accelerates the atomic diffusion and promotes the growth of precipitates.The DRXed ratio of Mg-5Zn matrix decreases with the increase of PDZ size,leading to the volume fraction and size of the precipitates decrease.In addition,the typical basal plane texture is formed of Mg-5Zn alloy after the compression deformation.The introduction of SiC_p does not change the texture type,but decreases the strength of basal texture,and the strength of basal texture of SiC_p/Mg-5Zn increases with the enlargement of PDZ size.The microstructure and mechanical properties of Mg-5Zn alloy and SiC_p/Mg-5Zn after the extrusion deformation were studied according to the influence of minor SiC_p and PDZ size on DRX and dynamic precipitation behavior of Mg-5Zn alloy.The addition of the minor SiC_psignificantly improves the yield strength(YS)and ultimate tensile strength(UTS)of SiC_p/Mg-5Zn;The YS and UTS of SiC_p/Mg-5Zn decrease with the increase of PDZ size,but the elongation increases.The strengthening mechanisms of minor SiC_p/Mg-5Zn are the fine grian strengthening mechanism,dislocation strengthening mechanism,precipitation strengthening mechanism and load transfer effect.However,the combined of action Zn and SiC_pleads to the significant refinement of Mg grains and the precipitation of Mg-Zn phase,which contributes greatly to the strengthening effect.The work hardening of the minor SiC_p/Mg-5Zn is accompanied by the softening effect during deformation.The addition of SiC_p results in the reduction of the work hardening effect,and improves the softening effect of Mg-5Zn alloy;the work hardening effect of SiC_p/Mg-5Zn increases with the largement of PDZ size,but the softening effect decreases.