| High performance2A12aluminum alloy was prepared by phase-transition coolingtechnology which was a novel rapid cooling methodology, and its dynamic aging behaviorwas studied too. Then the aging technique was optimized to improve the mechanicalproperties of the alloy.The mechanical properties of as-prepared2A12aluminum alloys were measures bytensile testing machine and micro-hardness tester. The micro-structure was studied byoptical microscope (OM), x-ray diffraction (XRD), scanning electron microscopy (SEM)and transmission electron microscopy (TEM); And aging behavior was analyzed usingdifferential scanning thermal analysis (DSC).The results shown that higher cooling rate could be obtained by phase-transitioncooling technology than it by the normal water cooling method. Which leading to refinedgrains and enhanced solidify solubility. So its mechanical properties were superior to thatof the alloy prepared by water cooling.Under the cooling rate of110℃/s, the aging sequence of the alloy was as α-Al→GParea→GP2area (S′′)→S. While under the cooling rate of250℃/s, the sequence wasα-Al→GP area→GP2area (S′′)→S′→S. The aging activation energy (43.14kJ/mol)at the cooling rate of250℃/s was lower than that at110℃/s (56.82kJ/mol), the newphases could precipitate more easily.The optimized aging technique of2A12aluminum alloy prepared by phase transitioncooling technology was:130℃aging for10h, which was lower aging temperature andshorter time, but a higher tensile strength obtained compared to the conventional heattreatment methods. The tensile strength, yield strength and elongation rate were460MPa,270MPa, and12.7%, respectively.Aged at a relative low temperature (130℃), new phases precipitated dispersively andits amount also increases with the increase of aging time. Compared with the2A12aluminum alloy prepared by conventional method, the precipitated phases were refinedsignificantly in the sample which prepared by rapid phase-transition cooling. When the aging temperature was higher (180℃/s), large size precipitated phases could distributealong grain boundary and formed a continues networking pattern, which would lead to thedecrease in mechanical properties of aluminum alloy. |
