Research On Mechanical Properties Of Ultra-fine Grain AZ31Magnesium Alloy Prepared By Powder Metallurgy

Magnesium alloys have been widely used in areas such as aerospace, automotive,electronics due to their high strength, stifness, easier to recycle and a series of advantages.Block magnesium alloy materials with ultra-fine grained microstructure have excellentphysical, chemical and mechanical properties, which is one of the research hot spots inmaterial area. This paper proposes an efective way to prepare block ultra-fine magnesiumalloy and the main technological process: nanocrystalline powder-cold pressing-vacuumhot pressing-extrusion-rolling. Extrusion and rolling are the key points to prepare ultra-fine grained materials. In addition, the mechanical behaviors of ultra-fine grained AZ31magnesium alloy are significantly diferent from conventional materials at room temper-ature and high temperature. It is very important to establish the model of mechanicalbehavior of ultra-fine grained materials.Research on grain degrees, morphology, microstructure and hot stability of nanocrys-talline AZ31magnesium alloy powder. The grain sizes increase with annealing tempera-ture and annealing time increasing. Discussion has been done on grain growth behavior ofnanocrystalline AZ31magnesium alloy powder. The grain growth index n and activationenergy G have been calculated, which shows as the basic work for the following vacuumhot pressing, extrusion and rolling. Studying on cold compactability of nano-grain mag-nesium alloy powder by Huang Peiyun compaction equation as experiment instruction ofcold pressing, hot pressing and extrusion, ultimately determined for nanocrystalline mag-nesium alloy powder preparation method of ultra fine-grained AZ31magnesium alloymaterials, optimizing the process parameters, to compact ultra fine-grained AZ31magne-sium alloy materials.Research on microstructure stability of ultra-fine AZ31magnesium alloy to deter-mine the optimum temperature of hot working process. Discussion on the efect of dif-ferent grain size on microstructure and properties and the results show the grain sizes ofAZ31magnesium alloy significantly efect the yield strength and the hardness. For theultra-fine grained AZ31magnesium alloy, its yield strength and grain size are still goodto meet traditional of Hall-Petch relationship.Research on mechanical behavior and deformation mechanism of ultra-fine magne-sium alloy. Preparation of ultra-fine grained AZ31magnesium alloy rod by extrusion at diferent temperature and its tensile strength at room temperature is382MPa, yieldstrength is278MPa. Rolled ultra-fine grained AZ31magnesium alloy sheet shows tensilestrength at room temperature is435MPa and yield strength is330MPa. Ultra-fine grainedAZ31magnesium alloy is strain rate sensitivity material for yield strength increasing withthe strain rate increasing.Gleeble-3500drawing simulation testing machine is taken to study on mechanicalbehavior of ultra-fine AZ31magnesium alloy at high temperature. An Analysis on hotflow stress with the deformation degree, tensile deformation strain rate and deformationtemperature have been done. Establishing the constitutive equations of flow stress, strainand Zener-Hollomon parameters to determine the material constants of thermal deforma-tion. Proposing reasonable thermal processing technology reference for hot working ofultra-fine grained AZ31magnesium alloy. Discussion on superplastic deformation mech-anisms of AZ31magnesium alloy materials and the establishment of appropriate models.