Preparation And Microstructure Of Ti Particles Dispersion Reinforced Bimodal Magnesium Matrix Composites

Magnesium has low density and abundant reserves,which makes magnesium and its alloys have unique advantages that other metals can't compare,and has good application prospects in the fields of energy saving,consumption reduction and lightweight.However,the shortcomings of low strength,low hardness,and low rigidity limit the wide use of magnesium and its alloys in industry.Magnesium martix composites combine the excellent properties of magnesium and its alloys,and at the same time overcome the shortcomings of magnesium and its alloys such as low hardness and low absolute strength,and become an attractive choice for structural applications.However,the plastic loss of ceramic particle reinforced magnesium matrix composites is a common and troublesome problem.The metal particles have better deformability,which can increase the strength while reducing the plastic loss of the material.The emerging spark plasma sintering technology has the advantages of fast sintering speed and high density of sintered green materials.Combining the dispersion strengthening of metal particles with the powder metallurgy process based on spark plasma sintering is expected to bring beneficial effects to the preparation of high performance magnesium matrix composites.Therefore,the powder metallurgy technology of “high energy ball milling + spark plasma sintering” was used to prepare magnesium matrix composites strengthened by particle reinforcement and bimodal grain size distribution.X-ray diffraction,optical microscopy,scanning electron microscopy and other analytical methods were used to observe and analyze the microstructure of the materials,which Ti particle reinforced magnesium matrix composites are used as the research object in this paper.The relative density and mechanical properties of the materials were tested and analyzed.The effects of the high energy ball milling process parameters on the microstructure and particle morphology of pure magnesium were discussed.The optimal process parameter matching was obtained for the preparation of nanocrystalline pure magnesium powder.The ultrafine grained pure magnesium powder were consolidated by spark plasma sintering technology.The densification behavior and sintering mechanism of pure magnesium in the spark plasma sintering process were revealed.The effects of sintering temperature and time on the relative density,microstructure and mechanical properties of pure magnesium were discussed.It provides the basis and reference for the preparation of composites and the design of reasonable sintering parameters.Based on this,the Ti particles reinforced bimodal magnesium matrix composites were obtained.Through observation,testing and analysis of the microstructure and mechanical properties of the composites,the results show that the Ti particles reinforced bimodal magnesium matrix composites have higher hardness,compressive strength and failure strain because of the existence of metal Ti particles.When the content of Ti particles is 3wt.%,the hardness,compressive strength and failure strain are increased by 22%,38%,and 35%,respectively.The main strengthening mechanisms of Ti particle reinforced bimodal magnesium matrix composites were dislocation strengthening,fine grain strengthening,load transfer strengthening,and its fracture mode was mixture of brittle fracture and ductile fracture.