Elastic Stress-spheroidization Treatment Of Magnesium Alloy AZ80

Magnesium alloy is one of the lightest structural metal materials in industrialapplications. AZ80magnesium is a kind of typical alloy with8%aluminum content, highstrength, good application prospects and it can be strengthened through aging. Whileconventional heat treatment processes have limitation in optimizing material properties, inrecent years the introduction of elastic stress is a new method in the heat treatment toimprove the mechanical properties.In order to improve the mechanical properties of magnesium alloy and shorten thetreatment time，the stress spheroidization mechanisms of AZ80magnesium alloy afterelastic stress spheroidization were studied in this paper. First,First, the solid solution, spheroidization process parameters were confirmed, andelastic stress range is confirmed through high temperature tensile curve, so did the specificexperimental process. Then the mechanical properties of AZ80magnesium was tested andthe microstructure was analysed. The best spheroidization process was obtained afteranalyzing the effect of spheroidization time, spheroidization temperature, furnace coolingand spheroidization stress on the mechanical properties of alloys. Hereafter, themicrostructure and the fracture surface of AZ80magnesium was characterized by opticalmicroscopy, SEM, TEM, the phase and elemental composition were identified by XRD, EDSand Kikuchi line analysis. The effect of stress spheroidization on the mechanicalproperties, stress spheroidization mechanism and fracture mechanism of AZ80magnesiumalloy were discussed at last.The results shows that: The best spheroidization process is solid solution at400℃for10h，air cooling to240℃, then insulation for2h with35MPa stress. After that, theVickers hardness, yield strengths, ultimate tensile strengths and uniform elongation were85.92,93.2MPa,199.155MPa and11.36%, respectively increased by2.3%,23%,4.3%and4.5%compared with the alloy after spheroidization treatment without stress.The microstructure of magnesium alloy after stress spheroidization was consist oflamellar shaped discontinuous precipitation phase, irregular short rods shape discontinuous precipitation phase, continuous precipitation and magnesium matrix. Thelamellar discontinuous precipitates sphered and continuous precipitation phase precipitatesin the process of spheroidization. Elastic stress accelerates the sphere process ofdiscontinuous precipitates and promotes the growth of continuous precipitates.During the stress spheroidization, elastic stress doesn’t lead to the formation of a newphase. The elastic stress acts on through-thickness direction, increasing the lamellar phasediscontinuous precipitation strain energy, promoting the plies twisted and disconnect.Elastic stress is conducive to the vacancy mechanism diffusion of aluminum atoms, whichpromotes the continuous phase precipitates growth.