Effects Of Alloying And Hot Deformation On Structure And Property Of Mg-Zn-Mn-Ce Alloy

Mg-6Zn-1Mn（ZM61） alloy is a new kind of high performance wrought magnesium alloy,which possesses high strength through high Zn addiction. ZM61alloy is more attractive forengineering applications due to the combination of relatively simple smelting method, lowmaterial cost’, whats more, the strength after two-step aging is corresponding to ZK60alloy.However, the development of ZM61alloy is restricted by coarse grains, low profiled, poorheat resistance, the large trend of microporosity and hotness. Therefore，it is necessary toimprove the comprehensive performance of ZM61alloy by means of adding new low-pricedalloying elements. Flow stress is one of the basic properties of material which is not onlyaffected by alloy chemical component, deformation temperature, deformation degree，strainrate, but also has a close relationship with the microstructure evolution, which will deifnitelyhas important signiifcance for the establishment of hot working process and metal plasticdeformation theory research.Firstly, based on our previous research results of optimized composition, in this study wehave selected the Mg-6.0Zn-l.3Mn-l.0Ce alloy as the base system, and have researched theeffect of Cu addition on the microstructure and aging characteristic. The results show that:（1）Cu addition makes the eutectic organization to produce CuMgZn new phase. With theincrease of Cu content, the grain size of cast alloy is reifned，the eutectic transformationtemperature is improved, and the eutectic organization is coarsening. Adding0.5%Cu alloyelement is the optimum combination of components in the quinary system. The tensilestrength and elongation reach223.7MPa,15.35%.（2）After two-stage aging treatment, the Mg-6.0Zn-l.3Mn-1.0Ce-0.5Cu alloy achievesthe best mechanical properties, whose Brinell hardness, room temperature tensile strength andelongation reach81.3HBW,261.3MPa,5.89%, respectively. Besides，the high temperaturetensile strength and elongation reach180.7MPa,21.66%.Therefore, in this paper Mg-6.0Zn-l.3Mn-l.0Ce-0.5Cu alloy which is the best alloycomposition is selected for hot compression simulation experiment. The analysis resultsindicate that:（l）When the compression is carried out at the temperature between250?400。C andstrain rate between1.0s₁?10s₁, lfow stress curve shows obvious characteristics of dynamicrecrystallization. When the temperature between250?400°C and low strain rate （0.1s-1），lfowstress curve displays characteristics of dynamic recovery. Under the temperature between 250?400°C and high strain rate (50s¹)，alloy appears the phenomenon of discontinuousyielding. With the increase of deformation temperature, the phenomenon of discontinuousyielding becomes obvious.（2）Whenthe deformation temperature between250?400°C and strain rate between0.1⁵0s^-1, high temperature compression deformation makes the organization to produce thedynamic recrystallization. Along with the increase of deformation temperature and strain rate,the degree of recrystallization increases gradually. The DRX at intial grain boundaries ischaracterized of dis-continuous DRX mechanism, while the DRX at intial grain cores ischaracterized of continuous DRX and twin-based dynamic recrystallization.（3）Precipitatedphase mainly includes rod shaped （MgZn₂），plate-like P2（MgZn₂）,long shaped CuMgZn and granular a-Mn simple substance through two-stage aging. Producedby compression deformation，dislocation defect improves the number, distribution of theprecipitated phases. Precipitated phases can pin dislocation and strengthen the matrix further.