Microstructure And Mechanical Properties Of TiC_p/ZX405 Magnesium Matrix Nanocomposite After Hot Deformation

In this study,the Mg-4Zn-0.5Ca?ZX405?alloy was selected as the as-received material and TiC nanoparticulates were selected as the reinforcing particle.xTiC_p/ZX405?x=0.2,0.5,1,2 wt.%?magnesium matrix nanocomposites were successfully synthesized through the ultrasonic-assisted semisolid stirring method,and followed by hot deformation.The effect of hot deformation process on microstructure and mechanical properties of TiC_p/ZX405 nanocomposites were investigated systematically.The results show that the external addition TiC nanoparticles refined the grain size of the matrix alloy,and improved the morphology of eutectic Ca₂Mg₆Zn₃ phases.The morphology of Ca₂Mg₆Zn₃ phases from block-like to particles-like and the grain size of as-cast nanocomposites is significantly refined with the increase of TiC nanoparticles content.The TiC_p agglomerations were found in the TiC_p/ZX405 nanocomposites with 1 wt.%and 2 wt.%TiC nanoparticles,which reduced the strength and elongation of nanocomposites.When the amount of TiC_p was 0.5 wt.%,superior mechanical properties with yield tensile?YS?of 75.7 MPa,ultimate tensile strength?UTS?of 204.7 MPa and elongation?EL?of 16%were obtained for the TiC_p/ZX405 nanocomposite.The grains in the as-extruded 0.5%TiC_p/ZX405 nanocomposites were obviously refined by comparing with the as-cast nanocomposites,and an enormous amount of MgZn₂ precipitates were observed in all the as-extruded nanocomposites.With the decrease of extrusion temperature,extrusion rate and extrusion ratio,the average sizes of DRXed grains(d_DRX)were significantly refined and the volume fraction of MgZn₂ phases were greatly improved.The mechanical properties of as-extruded 0.5%TiC_p/ZX405 nanocomposites were strongly affected by extrusion parameters.The YS and UTS increases with decreasing the extrusion temperature and extrusion rate,while the EL exhibits a decreasing trend.With the decrease of extrusion ratio,the YS?UTS and EL of as-extruded nanocomposites increased.Compared with the as-cast counterpart,the matrix grains in the as-extruded TiC_p/ZX405 nanocomposite with different TiC_p content were significantly refined.As the content of TiC nanoparticles in as-extruded TiC_p/ZX405 nanocomposite increased from 0.2 wt.%to 2 wt.%,the grain size of DRX gradually increases,while the volume fraction of MgZn₂phases exhibits a decreasing trend.With the increase of mass fraction of TiC_p nanoparticles,the fine-grained strengthening gradually decreases,the CTE strengthening gradually increases,while the Orowan strengthening was substantially retained.The Orowan strengthening was caused by MgZn₂decrease as the content of TiC_p increase,while the Orowan strengthening was caused by TiC nanoparticles exhibits a increasing trend.The grain size of TiC_p/ZX405 nanocomposite was refined obviously and the mechanical properties were improved after multidirectional forging?MDF?at 270?and 310?.With the increase of the MDF passes,the average sizes and volume fraction of DRXed grains and MgZn₂ phases were increased gradually.YS and UTS decreased gradually and EL increased gradually with the increase of the passes of MDF at 270?,while the mechanical properties exhibit the opposite variation trend at 310?.The grains in the TiC_p/ZX405nanocomposite after multistep deformation?MDF+ED?were significantly refined while the volume fraction of MgZn₂ phases was greatly improved compared with the nanocomposite after MDF.With the increase of forging passes before extrusion,the d_DRX of nanocomposite after MDF270+ED multistep deformation was increased gradually,while the d_DRX of MDF310+ED nanocomposite exhibits a decreasing trend.The grains of matrix in the TiC_p/ZX405 nanocomposite after extrusion were significantly refined,while the volume fraction of MgZn₂ phases was low.The multidirectional forging can refinement the grains of nanocomposite and facilitate the dynamic precipitation.After multistep deformation,the grain size of DRX was refined and the volume fraction of MgZn₂ phases was greatly improved,the strength of nanocomposites are thus improved.The nanocomposite after 3MDF310+ED nanocomposite exhibited the excellent mechanical properties,and its YS,UTS and EL were 404 MPa,450.3 MPa and 5.2%,respectively.