Microstructure And Properties Of Ti Particles Reinforced AZ31 Magnesium Matrix Composites

Due to the low density,high specific strength,specific modulus,and specific stiffness,magnesium matrix composites（MMCs）possess broad application prospects and market value in aerospace,military and automobiles industries.The commonly used reinforcements for MMCs are hard reinforcements,such as ceramics particles etc.During deformation process,the hard reinforcements connot coordinately deform with magnesium（Mg）matrix,which induces stress concentration at the interface between reinforcements and Mg matrix,and then significantly decreases the plasticity of MMCs.However,in the application of metal materials structure,materials often require the characteristics of high strength and good plasticity to ensure good structural stability.Besides,with the development of aerospace and automobile to lightweight,higher requirements have been placed on the mechanical properties and wear resistance of MMCs.Therefore,the development of MMCs with high strength,excellent plasticity and wear resistance is very important for their applications.In this work,Ti particles reinforced AZ31 MMCs are prepared by cold-press sintering,hot-press sintering and stir casting,respectively.The microstructure,interfacial structure,mechanical properties and wear resistance of extruded Tip/AZ31composites are investigated.The effect of the interfacial structure between Ti particles and Mg matrix on the grain refinement and mechanical properties of extruded Tip/AZ31composites is studied,which will provide theoretical supports for the development and application of high performance MMCs.The main results are as follows:（1）In Ti particles reinforced AZ31 composites prepared by cold-press sintering（Tip/AZ31-CPS）,Ti Al diffusion layer and continuous Mg O nanoparticles form at Ti/Mg interface.The Ti Al/Mg O interface is coherent interface and Mg O/Mg interface is semi-cohenrent interface.With the increment of Ti particles,the grain sizes of Tip/AZ31-CPS composites are significantly refined from 5.2μm to 2.5μm.The yield strength（YS）,ultimate tensile strength（UTS）,fracture elongation（FE）and wear resistance of Tip/AZ31-CPS composites are increased simultaneously.The 9wt.%Tip/AZ31-CPS composite shows the best comprehensive mechanical properties and wear resistance,with YS,UTS,FE and wear rate of 264MPa、294MPa、8.0%and 4.437×10^-3mm³/m,respectively.（2）In Ti particles reinforced AZ31 composites prepared by hot-press sintering（Tip/AZ31-HPS）,Al₃Ti diffusion layer and discontinuous Al₈Mn₅ submicron-particles form at Ti/Mg interface.Al₃Ti/Mg,Al₃Ti/Al₈Mn₅,Al₈Mn₅/Mg interfaces are incoherent interface.Besides,<c+a>slips are activated in the vicinity of Ti particles,which contributes to the plasticity of Tip/AZ31-HPS composites.With the increment of Ti particles,the grain sizes of Tip/AZ31-HPS composites are refined slightly from from5.8μm to 5.1μm.And the YS,UTS and FE of Tip/AZ31-HPS composites are increased slightlty.However,the formation of oxide film on worn surface stimulated by Ti particles,and the increased content of precipitates in Mg matrix greatly improve the wear resistance of Tip/AZ31-HPS composites.The 6wt.%Tip/AZ31-HP composite possesses the highest mechanical properties and wear resistance,with YS,UTS,FE and wear rate of 199MPa、290MPa、15.5%and 4.343×10^-3mm³/m,respectively.（3）In Ti particles reinforced AZ31 composites prepared by stir casting（Tip/AZ31-SC）,Ti Al diffusion layer and discontinuous Al₂Ti nanoparticles and Al₈Mn₅micron-particles form at Ti/Mg interface.Ti Al/Mg,Ti Al/Al₂Ti,Al₂Ti/Mg interfaces are semi-coherent interface.Ti Al/Al₈Mn₅,Al₈Mn₅/Mg interfaces are incoherent interface.With the increment of Ti particles,the grain sizes of Tip/AZ31-SC composites were refined from 4.6μm to 3.3μm.The YS,UTS,FE and wear resistance of Tip/AZ31-SC composites are increased simultaneously.The 6wt.%Tip/AZ31-SC composite possesses the best comprehensive mechanical properties and wear resistance,with YS,UTS,FE and wear rate of 245MPa、327MPa、20.4%and 9.206×10^-3mm³/m,respectively.（4）Ti particles show various efficiency in refining the grains of Mg matrix in the Tip/AZ31-CPS,Tip/AZ31-HPS and Tip/AZ31-SC composites.The microstructure,interfacial structure and mechanical properties of the Tip/AZ31-CPS,Tip/AZ31-HPS and Tip/AZ31-SC composites were comparatively analyzed.Compared to the submicron/micron interface products and incohenrent interface,the nano interfacial products and semi-coherent interface show higher efficiency in refining the grains of Mg matrix,which more effectively improve the mechanical properties of MMCs.