7A55铝合金在常规RRA和连续RRA处理过程中的性能及组织演变

Microstructural Evolution and Properties of 7A55 Aluminum Alloys during Conventional RRA Treatment and Continuous RRA Treatment

摘要:

测试7A55铝合金在常规RRA和连续RRA处理过程中不同状态点的抗拉强度和电导率，并通过TEM 观察 7A55铝合金在常规RRA处理和连续RRA过程中的微观组织演变。结果表明，7A55铝合金无论采用常规RRA处理还是连续RRA处理，在高温回归过程中，晶内析出大量与基体不共格相（大量η′相和一些η相），同时晶界η相严重粗化并出现无沉淀析出带，电导率有大幅上升。另外，采用连续RRA处理工艺，1级时效后在适当的升温速度下，直接升温至回归温度进行回归处理，可以获得接近第1级时效的强度和38.1%IACS的电导率。

Abstract:

The tensile properties and electrical conductivity of 7A55 aluminum alloys at different states during RRA conventional treatment and RRA continuous treatment were tested and the microstructure evolution in the two periods was observed by TEM. The results show that either after conventional RRA treatment or after continuous RRA treatment, the alloy is composed of a large number of metstable η′ phase precipitates and a few η phase precipitates in grains; η phase precipitates are coarsened seriously and PFZ (precipitate free zone) appears at the grain boundaries; the electrical conductivity is greatly increased during the retrogression step. In addition, after the first step treatment without air cooling, heated to the retrogression temperature at a proper heating rate, the 7A55 alloy can obtain the strength near the first step aging levels together with the electrical conductivity of 38.1%IACS in continuous RRA treatment.