Research On Quick Plastic Froming For A Viation In Strument Panel Of AZ31 Magnesium Alloy

Magnesium alloys are wildly used in many fields for its outstandingperformance. Due to a closed-packed hexagonal (hcp) crystal structure, magnesiumalloy has a poor plasticity at room temperature and a limited forming ability.Superplastic gas buling is an important sheet metal forming method. Superplasticforming process is simple and effective, but the forming efficiency is low, therebyincreasing the efficiency of this process is necessary. Based on this object, quickplastic forming(QPF) is used in the aviation instrument panel made of AZ31magnesium alloy to research the forming ability of quick plastic forming.Material parameters for fine-grained AZ31 magnesium alloy sheet related toQPF are investigated through uniaxial hot tensile tests. Flow stresss and elongationsunder different temperature and strain rate are compared and the optimumtemperature and strain rate for material forming are discussed. The results show thatas deformation temperature rises, the material deformation resistance decreases andthe elongation increases. As the deformation rate increases, material deformationresistance increases while the elongation decrease. At 400℃, AZ31 magnesiumalloy still show superplasticity under high strain rate. As the temperature increases,fracture behavior changes from dimple fracture to inter granular fracture.Hemisphere bulging tests are performed under different temperatures andpressure to survey forming limitation in biaxial tension stress state and study theeffect of the bulging parameters on thickness distribution of hemisphere part. Theinfluence of temperature, strain and strain rate on microstruction evolution areinvestigated by observe metallographic structure of material and SEM image offracture surface. Experimental results show that grain size increase as deformingtemperature rise. Recrystal grain was found in microstruction and mean grain sizedecrease. Cavity appears at grain boundary and grows when the total deformationdegree increases. Cavity growth strain controlled growth and diffusion controlledgrowth.Finite element analysis software MSC.MARC is used to analyze the influenceof strain rate sensitivity index m, frictin coefficient and gas pressure on QPF ofaviation instrucment panel and determine the optimum gas pressure load path. Numerical results show that the material has maximum initial strain rate when thesheet start deformation and the sheet metal tends to fracture at the circular bead ofthe female die because of excessive thinning caused by larger strain rate. Themaximum deformation are close to the circular bead at the bottom of the female die,if pressure is too high or deforming time last too long, sheet will broke because ofexcessive deformation.The QPF experiments for aviation instrument panel are carried out wirh 1.5mmthick AZ31 magnesium alloy sheet. The experimental results show that the formingcan be achieved in 5min, and the thickness and shape is acceptable, the mechanicalproperty does not decline much. The loading curve must be designated particularlyin experiments.The QPF process of aviation instrument panel made of magnesiu alloy can beimproved through changing the shape of obturating ring,performing sheet,givingback pressure, changing the dimension of the forming die and improvinglubrication condition between die and sheet. All of those methods can improve theformability of the blank, make the thickness distribution more uniform and increasethe minimum thickness of the sheet.