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以A356合金为研究对象,采用复合细化变质、微合金化和T6热处理的方法制备了5种A356合金,研究了合金的力学性能、显微组织和不同温度幅下的热疲劳性能,并分析了热疲劳裂纹的生长行为和产生机理。结果表明,经过复合细化变质、微合金化和T6热处理可以使A356合金的力学性能得到提高;经过T6热处理后,复合细化变质和复合细化变质+微合金化的A356合金中共晶Si的形态由针片状转变为颗粒状,共晶Si棱角圆整化程度提高提高,铸态A356合金的热疲劳寿命得到延长;在温度幅下限不变的前提下,合金的热疲劳寿命随着温度幅上限的提高而逐渐降低;经过复合细化变质+微合金化+T6热处理后合金的裂纹萌生和扩展速率最低,热疲劳寿命最长。
A356 alloy was taken as the research object. Five kinds of A356 alloy were prepared by compound metamorphism, micro-alloying and T6 heat treatment. The mechanical properties, microstructure and thermal fatigue properties of the alloy were studied and analyzed. The thermal fatigue crack growth behavior and mechanism. The results show that the mechanical properties of A356 alloy can be improved by compounding metamorphism, micro-alloying and T6 heat treatment. After T6 heat treatment, the eutectic Si in A356 alloy with compound metamorphism and metamorphism metamorphism + micro-alloying The morphology changed from needle-like to granular, and the degree of roundness of eutectic Si edges increased. The thermal fatigue life of cast A356 alloy was prolonged. Under the condition of the same temperature range, the thermal fatigue life of the alloy increased with the increase of temperature The upper limit of the steel sheet is gradually reduced; the crack initiation and propagation rate of the alloy is the lowest after thermal treatment with the compound metamorphism + microalloying + T6, and the longest thermal fatigue life.