Research On Microstructure And Properties Of Solid Phase Regenerative SiC/Mg-Gd-Y-Zn-Zr Magnesium Matrix Composites By Equal Channel Angular Pressing

With the continuous improvement of the global industrial level,the demand for magnesium and magnesium alloys in social industries has gradually increased.The wide application of magnesium alloys is also accompanied by huge waste of materials,which not only destroys the environment but also causes huge losses to the national economy.cost burden.Therefore,exploring a suitable recycling process can not only save resources,but also reduce production costs.In this paper,the as-cast Mg-Gd-Y-Zn-Zr alloy is used as the original billet,and a complete process flow is designed to study the solid phase regeneration of magnesium alloy waste.The specific regeneration process is to first perform solution treatment on the as-cast alloy to meet the usage habits of magnesium alloys,then perform cutting processing on the homogeneous alloy,and use the ball milling process to compound magnesium alloy chips and sic particles to obtain reinforced composite materials..The obtained rare earth magnesium alloy scraps and composite material scraps are then hot-pressed and sintered to obtain magnesium alloy solid-phase regeneration billets.The performance of the solid-phase recycled billet is far from the requirements for use.Therefore,the equal-channel angular extrusion experiment was performed on the solid-phase recycled billet to prepare ultra-fine grained materials,which effectively improved the mechanical properties of the recycled billet.The tensile strength of the as-cast rare-earth magnesium alloy is 242 MPa and the elongation is 7.8%.The reticular eutectic structure and casting defects in the grain boundaries seriously affect the mechanical properties of the alloy.After homogenization,the eutectic phase disappears.The LPSO phase distributed in the intergranular and intragranular is left,and the mechanical properties at room temperature are effectively improved.The tensile strength is 243.9 MPa,and the elongation is 10.4%.Compared with the as-cast alloy,the elongation is increased by33.3%.The solid-phase regeneration behavior of magnesium alloys is mainly that under the action of high temperature and high pressure,a layer of oxidation bonding interface is formed between the debris and the debris through the oxidation reaction.The oxide phase is a brittle phase,and SiC has a hindering effect on the bonding between chips,so the plasticity of the regenerated alloy blank is very poor,and the elongation of the rare earth magnesium alloy solid phase regenerated blank is 2.3%,1%,3%,5% The elongation of the solid-phase recycled billets of %SiC reinforced magnesium matrix composites are 1.75%,1.39%,and 1.03%,respectively.The solid-phase recycled alloy obtained by the hot pressing sintering process needs a certain extrusion deformation to improve the comprehensive mechanical properties.The ECAP experiment is related to the die structure,extrusion temperature,extrusion path and other factors.The finite element simulation of the rare earth magnesium alloy solid-phase recycled billet ECAP is carried out by Deform software,and it is found that the core metal flow of the ECAP part is the most uniform and the equivalent strain degree maximum.Increasing the extrusion temperature and increasing the fillet radius can effectively improve the forming quality of the first-pass extrusion parts.The selection range of the fillet radius is(3～6)mm,and the selection of the extrusion temperature needs to be based on the actual situation.The growth of recrystallized grains in the extrusion process is reasonably selected.Through the actual exploration of the ECAP process,it is found that the forming quality of the extruded parts under the path of 475℃,r=5mm,and Bc is the highest.Under the experimental parameters,four passes of ECAP experiments were carried out on the solid-phase regenerated alloy,and the room temperature mechanical properties of the obtained extruded parts were the best in two passes.Among them,the tensile strength of the 2-pass ECAP parts of the rare earth magnesium alloy solid-phase recycled billet treated by ball milling is the highest,reaching 307.1 MPa,which is 26% higher than that of the homogeneous alloy.The2-pass ECAP preparation of 1% SiC reinforced magnesium matrix composites The elongation of the piece is the best,reaching 11.2%,an increase of 7.6%.The high-temperature tensile properties of 2-pass extrusions of all materials were tested,and it was found that the extrusions without SiC had the best high-temperature mechanical properties,and the extrusions with 5% SiC content in the composite material had the highest strength.The study found that after hot pressing and sintering,the recycled scraps need to be treated with large deformation to achieve the purpose of improving performance.The strengthening effect of SiC must comprehensively consider the relationship between the grain size after dynamic recrystallization and the size of SiC particles.