回归再时效工艺对7055铝合金板材组织及性能的影响

通过TEM、SEM、DSC等分析及拉伸试验、电导率测试，对7055铝合金板材回归再时效后的显微组织、性能进行了系统研究。结果表明，随着回归时间的延长，回归再时效处理后的合金强度先升高后降低，导电率单调升高。与T6态相比，合金经回归再时效处理后，晶界析出相间距变大，呈断续分布，且晶内强化相的尺寸也发生了一定程度的粗化。当合金板材的回归再时效工艺为121℃×24 h+170℃×30 min+121℃×24 h时，7055铝合金板材的综合性能最优，抗拉强度达630.75 MPa,屈服强度达588.75 MPa,导电率达34.75%IACS,断裂机制为混合型断裂。

Effects of retrogression and re-aging process on microstructure and properties of 7055 aluminum alloy sheet

Microstructure and mechanical properties of 7055-aluminum alloy sheet after retrogression and re-aging were systematically studied by means of TEM, SEM, DSC, tensile test and conductivity testing. The results show that with the extension of retrogression time, strength of the alloy increases firstly and then decreases, meanwhile, the conductivity monotonically increases through the whole process. Compared with T6 state, after retrogression and re-aging, the precipitated phase space on grain boundary increases and intermittently distributes, and the size of strengthening phase in the crystal is grown to a certain extent. When the retrogression and re-aging process is 121 ℃×24 h+170 ℃×30 min+121 ℃×24 h, the 7055 aluminum alloy exhibits excellent comprehensive properties, of which the tensile strength is 630.75 MPa, the yield strength is 588.75 MPa, the conductivity is 34.75%IACS, and the fracture mechanism is mixed fracture.