7050合金固溶后在180℃~250℃等温淬火时的析出行为

Precipitation behavior of 7050 alloy during isothermal quenching in 180℃~250℃ after solid-solution treatment

摘要:

本文研究了7050合金固溶后在180℃~250℃等温淬火过程中，合金的电导率、硬度与微观组织之间的关系。结果表明，7050合金在180℃和200℃等温淬火初期，等温样品的淬火态电导率低于固溶后直接水淬样品；随着等温时间延长，等温样品自然时效态硬度先升后降。7050合金在180℃等温128 min时，基体内形成GPΙ区和η’相；在200℃等温32 min时，基体内形成GPΙ区和部分GPΙΙ区；在250℃等温32 min时，基体内形成η’相和S相。合金基体内形成强化相是造成等温淬火初期合金自然时效态硬度上升的主要原因。7050合金固溶后在200℃等温淬火16 min，此时合金T6状态的硬度较固溶后直接水淬样品仅下降3.4%，而电导率上升达9.2%，性能接近回归制度为180℃-32min的RRA工艺处理后合金的性能，若将该等温淬火制度作为7050合金板材固溶后水淬前的预处理工艺，可使板材获得较好的综合性能。

Abstract:

In present work, the relationships between electrical conductivity, hardness and microstructures of 7050 alloy during isothermal quenching in 180℃~250℃ following solid-solution treatment were investigated. Results show that in the initial stage of isothermal quenching at 180℃ and 200℃, electrical conductivity of isothermal specimens is lower than that of the specimen direct water quenching following solid-solution treatment and with the increase of isothermal time, hardness of isothermal specimens in natural aging temper increases at first and then decreases. With isothermal quenching at 180℃ for 128 min GPΙ zones and η’ phases are formed in matrix, with isothermal quenching at 200℃ for 32 min GPΙ and GPΙΙ zones are formed in matrix, and with isothermal quenching at 250℃ for 32 min η’ and S phases are formed in matrix. The formation of strengthening phases during isothermal quenching is the main reason for the hardness of specimens increase in natural aging temper. When 7050 alloy plates are isothermal quenching at 200℃ for 16 min following solid-solution treatment, their T6 temper hardness is only 3.4% lower than that of the direct water quenching plates and their conductivity increases by 9.2%, which are close to the properties of RRA treated plates with the regression regime of 180℃ for 32 min. Therefore, taking isothermal quenching at 200℃ for 16 min as a pre-treatment process following solid-solution treatment it will make 7050 alloy plates obtain excellent comprehensive properties.