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采用差示扫描热量法(DSC)、硬度测试和拉伸试验研究重力铸造B356铝合金的时效硬化行为。人工时效温度分别为155、165和180°C,热处理时间为40 min~32 h。DSC结果表明,样品在低于室温的条件下(约为-10°C)形成团簇。由于团簇形成影响主要强化相β′′的后续沉淀过程,因此可以推断,固溶处理后不及时进行人工时效处理将对合金的力学性能产生不利影响。同时证实,在人工时效过程中(分别在155°C时效16 h,165°C时效6 h和180°C时效4 h)当β′′相生成完全后,合金的硬度和拉伸强度达到最大。经最高时效温度处理的样品其力学性能随时效时间的延长而降低,这与共格β′′相向半共格β′相的转变相关。最后计算得到与β′′相沉淀相关的活化能为57.2 k J/mol。
The differential scanning calorimetry (DSC), hardness test and tensile test were used to study the age hardening behavior of gravity cast B356 aluminum alloy. Artificial aging temperature were 155,165 and 180 ° C, heat treatment time is 40 min ~ 32 h. DSC results showed that the sample formed clusters below room temperature (about -10 ° C). Since the formation of clusters affected the subsequent precipitation of the major strengthening phase β ’’, it can be inferred that the failure of artificial aging after solution treatment will adversely affect the mechanical properties of the alloy. At the same time, it was confirmed that the hardness and tensile strength of the alloy reached the maximum during the artificial aging (16 h at 155 ° C, 6 h at 165 ° C, and 4 h at 180 ° C) . The mechanical properties of the samples treated with the highest aging temperature decrease with the aging time, which is related to the transition of the co-β ’phase toward the semi-coherent β’ phase. Finally, the activation energy associated with the β ’’ precipitates was 57.2 kJ / mol.