Study Of Volume Effect And Hot Processing Parameters On The Plastic Deformation Of AZ31

A mass of manufacturing practices showed that the plastic deformation behavior ofmetal was related to its volume(size). For instance, with the increase of the metalvolume, the uneven degree of the internal organization and chance of the possibledefects would go up, which make it easier to crack during the plastic deformation.Simultaneously, the state of the three-dimensional compressive resistance caused by theexternal friction weakened for the decrease of the relative surface area, which alsoleaded to the decrease of the plasticity. However, the existing researches (includingstandard experiment on testing material performance) studied the material plasticdeformation mainly in a certain size scope, taking seldom or no consideration of thevolume effect. For this purpose, the paper mainly studied the volume effect in bothMacro and micro perspectives and the influence of the thermal processing parameterson the plastic deformation of AZ31based on the hot compression test.There are three different sizes of the specimens in hot compression experiments(Φ6mm, Φ10mm, Φ14mm). The variable parameter Arrhenius flow stress model wasestablished based on the true stress-true strain curve, and the processing map was builtbased on the dynamic material model (DMM). The grain growth process of AZ31specimens with different sizes were simulated by Cellular Automaton. Main conclusionsare as follows:①Flow stress curve showed the sensitiveness of AZ31to the deformationtemperature and the strain rate, the hardening rate curve directly reflected the evolutionrule of the internal organization. The flow stress value can be accurately predicted bythe variable parameter Arrhenius hyperbolic sine flow stress model of AZ31.②The processing maps of the Φ10mm sized sample under different strainconditions shows that the processing diagram outline does not vary with strain, whichsuggests that AZ31is not sensitive to strain. According to the processing map candetermine the AZ31flow instability region and optimal processing region.③Flow stress curves of different sample size show that the peak stress increaseswith the increase of the specimen diameter. The curve of the Φ14mm sized samplediffers from the others, the flow stress curves to the balance with the increase ofdeformation temperature at last. The processing maps in different size show that theflow stress instability area distribution is different, and the flow stress instability area increases with the size decrease. The side of the Φ6mm sized specimen cracks after hightemperature compression test.④The analysis of the simulation shows that the size effect makes a big differencein the internal stress and strain distribution of the deformed metal. When the diameter ofthe deform metal is less than20mm, the behavior parameters of the deformed metalchange much more with the change of the body size. When the diameter of the deformmetal is more than50mm, the behavior parameters of the deformed metal change muchless with the change of the body size. When plastic deformation occurs to the similardeformed metals under the same condition, the influence rules of the volume effect tothe behavior parameters is similar.⑤The grain growth is simulated by Cellular Automaton, it is found that thevolume effect is not obvious when the strain value is small, with the increase of thestrain value, the track around grain size changes much more intensely when thediameter is bigger, which shows the intense change of the internal microstructureevolution.