7050合金RRA沉淀析出的TEM研究

TEM observation of precipitates in a 7050 alloy after RRA treatment

采用透射电镜 ( TEM)和维氏硬度计研究了回归再时效 ( RRA)处理对 70 50合金的的影响。研究发现 ,70 50合金受回归温度和时间影响。当回归温度为 453K和 473K时 ,回归曲线由三部分组成 ,回归再时效曲线由两部分组成。与在回归曲线上存在的峰值硬度相比 ,回归再时效峰值硬度要高。 TEM观察表明 ,硬度谷值的产生与 GP区的回溶有关 ,而峰值的产生与η′和η相的沉淀析出有关。回归再时效峰值高于回归峰值 ,这与回归再时效过程中 η和 η′相沉淀析出数目增加有关。当回归温度为 493K,回归和回归再时效曲线单调下降 ,分析认为由于回归温度高 ,回归曲线上不能区分 GP区的回溶、η和 η′相形核、η和

alloy precipitation aging behavior has been studied by transmission electron microscopy and Vickers hardness tester after retrogression and reaging(RRA) treatment. The RRA behavior was affected by the retrogression temperature. When the retrogression temperature was at 453K and 473K, the retrogression curve can be dealt with in three stages and the RRA treatment can be simply considered as a two step aging process. The result of TEM showed that the dissolve of GP zone caused the decrease of hardness and the precipitation of η and η′ caused the increase of hardness. When the regression temperature was 493K, the hardness decreased, and no hardness valley and peak was not observed on the retrogression curve and RRA curve. Analysis indicated that the three stages of dissolve of GP zone, precipitation of η and η′ and growth of η and η′ can not be distinguished at the retrogression curve because of higher retrogression temperature.[KH3/4D]