Study On The Evolution Of Mg-10Gd-3Y-2Ag (-0.4Zr) Alloys Processed By Rolling Deformation

As one of the most promising and most challenging metal structural materials,magnesium alloys can be used as a good choice for the next generation of light vehicles,space shuttle and electronic communications.As a good lightweight structural material,magnesium alloy can reduce more than 50%of structural components and system weight on traditional cars.However,there are relatively few magnesium alloys used in commercial industrial products in real life,which are mainly challenged by various technologies,and the development is not mature.Therefore,the preparation of high performance magnesium alloys also has a huge technical space.In this paper,Mg-10Gd-3Y-2Ag-0.4Zr alloy was used as the research object.The deformation treatment of magnesium alloy was carried out by accumulative rolling.The effect of different heat treatment and deformation process on the microstructure and mechanical properties of Mg-10Gd-3Y-2Ag-0.4Zr alloy was analyzed.The alloy was mainly studied and analyzed in the cold rolling and hot rolling of high strength rare earth magnesium alloy.The strengthening mechanism is analyzed and solved the technological problem of preparing high-strength rare earth magnesium alloy.The effect of different processes of the alloy was analyzed by compression test with Gleeble-1500 thermal simulator,and the mechanism of the effect of deformation temperature and strain rate was analyzed by compression test.The activation energy by hot compression of Mg-10Gd-3Y-2Ag-0.4Zr alloy is170.417kJ/mol.The constitutive equation of the alloy is obtained by changing and calculating the alloy Arrhenius equation.The constitutive equation of the flow stress of Mg-10Gd-3Y-2Ag-0.4Zr alloy with high temperature is as follows:σ_p=（122.35）{(Z/8.6×10¹¹)^1/4.16+[(Z/8.6×10¹¹)^2/4.16+1]^1/2}With the constitutive equation,the numerical simulation software DEFORM is used to analyze the stress,strainand temperature of the alloy under different deformation temperature and cumulative deformation.Through the stress field analysis,it is known that during the alloy rolling process,significant stress concentration occurs at the boundary position of the alloy,and defects such as cracks are most likely to occur at the boundary position,especially on both sides of the thin plate in the rolling direction.As the amount of rolling deformation increases,the crack is most likely to occur at the boundary of the rolled sheet,so the rolling deformation of Mg-10Gd-3Y-2Ag-0.4Zr is controlled to be less than 80%.The highest effective stress of the alloy during rolling is between 500MPa and 600MPa.According to the analysis of strain field,the distribution of strain is not uniform when the deformation is small.With the increase of deformation to 80%,the non-uniformity of strain distribution is improved obviously,and the maximum strain is to⁴.0.According to the analysis of the temperature field,the cooling rate of the alloy plate is faster due to the heat transfer of the cooling roll（25℃）during the rolling process.The rolling temperature is 450℃and the deformation is 20%-80%.The temperature of the alloy after the manufacture is significantly reduced by about100°C.Rare earth magnesium alloy can be synergistic strengthened by refining grain and precipitation.A step cold rolling+short time high temperature annealing technology is put forward in this paper.Compared with the conventional hot rolling,the grain size can be refined from 100μm to 20μm at 40%down rolling,while the grain size of about 30μm can be achieved when the current rolling volume is 80%.In addition,the aging precipitation enhancement effect is significantly higher than that of the hot rolled sample,the increase of the hardness value is 60HV,which is as twice as that of hot-rolled sample.since the effective suppress of dynamic precipitation by the two-step forming process,the density of precipitation at grain boundary is far less than that in hot-rolled sample;And after aging,the density of precipitation for Mg alloy from the two-step processing route,in particular ofβ’precipitation,is much higher than hot-rolled Mg alloy.The experimental results show the effectiveness of the process for strengthening rare earth magnesium alloys.