7050铝合金在回归加热过程中的组织演变规律

Microstructure Evolution Rules for Aluminum Alloy 7050 during Retrogression Heating up

采用差示扫描量热法(DSC)、高温X射线衍射(HTXRD)、透射电镜(TEM)观察、硬度测试以及电导率测试等手段,研究了不同的加热速率(340,57,4.3℃·min-1)对7050铝合金在回归加热过程中组织演变的影响。结果表明:在回归加热过程中,预时效态组织的GP区和η′相将发生回溶或依次转变为η′相和η相,而且回归加热速率对回溶和转变的温度产生显著影响,随加热速率提高,回溶和转变的温度升高。在一定的回归温度下,不同的加热速率使得合金在加热至回归温度时较预时效态具有不同的组织结构,从而影响合金在回归阶段发生不同的组织转变。本研究认为中等加热速率下,预时效态组织在加热至回归温度时所获得的组织结构最有利于回归阶段的组织转变。

The effects of the retrogression heating rates（340,57,4.3 ℃·min-1） on the microstructure evolution of aluminum alloy 7050 during retrogression heating up were investigated by means of differential scanning calorimetry（DSC）,high temperature X-ray diffraction（HTXRD）,transmission electron microscopy（TEM）,hardness measurement and electrical conductivity testing.The results show that during the process of retrogression heating up,the pre-aged microstructures suffer the process of GP zone and η＇ phase re-solution,or the phase transformation from GP zone and η＇ phase into η＇ phase and followed η phase,respectively.And the heating rate affects evidently the temperature of re-solution and phase transformation.With the heating rates increasing,the temperature of re-solution and phase transformation rises,too.When the retrogression temperature is affirmatory,the microstructures formed during heating up process are different due to the various heating rates.And this kind of microstructure will affect the phase transformation at the retrogression stage.This work thinks that at the medium heating rate,the microstructures formed during heating up process are more propitious to the microstructure transformation at the retrogression stage.