LD7铝合金淬火敏感性及相变动力学规律  

Quench Sensitivity and Phase Transformation Kinetics of LD7 Aluminum Alloy

作　　者：江道 易幼平[1,2] 黄始全[1] 

机构地区：[1]中南大学高性能复杂制造国家重点实验室 [2]中南大学轻合金研究院

出　　处：《材料导报》2017年第12期140-144,共5页Materials Reports

基　　金：国家重点实验室自由探索课题(zzyjkt2014-02);江苏省科技计划(BA2015075)

摘　　要：通过分级淬火的方法,结合所测LD7铝合金淬火态电导率和时效态硬度拟合出合金的时间-温度-转化率(TTT)曲线和时间-温度-性能(TTP)曲线。利用透射电镜(TEM)和Johnson-Mehl-Avrami(JMA)方程研究了铝合金等温淬火过程中的组织变化和相变动力学规律。结果表明:LD7铝合金TTT和TTP曲线的鼻尖温度均为350℃,孕育期约为2s,淬火敏感区间为290~410℃;等温保温过程中过饱和固溶体析出第二相粒子,鼻尖温度附近析出速率最快;随保温时间的延长,第二相富集长大且粗化,无沉淀析出区域变宽,晶界第二相连续化,导致合金强化效果下降;根据相变动力学方程拟合出的S曲线,解释了合金在350℃附近淬火敏感性最大以及淬火敏感区间合金第二相主要以针状形态析出的规律。The quench sensitivity of LD7 aluminum alloy was determined by the time-temperature-transformation （TTT） curves and time-temperature-property （TTP） curves by an interrupted quench technique with measurement of as-quenched electro- conductivity and as-aged hardness. The microstructure evolution and phase transformation kinetics during isothermal quenching treat- ment were studied by the transmission electron microscopy （TEM） and Johnson-Mehl-Avrami （JMA） equation. The results showed that the nose temperature of TTT curves and TTP curves were both about 350 ℃, and the incubation period was about 2 s, with the quench sensitivity range of 290- 410 ℃. The supersaturated solid solution decomposed and particles precipitate during quench process; the precipitation rate was the highest at the nose temperature. Prolonging holding time leads to bigger and coarser second phase particles and widened precipitation free zone in the matrix, more spaced second phase particles precipitated at the grain bounda- ry, which resulted in the loss of solutes and decrease o{ subsequent aging hardening effect. The fitted S-curve according to the phase transformation kinetics equation explained that the precipitation rate was the highest at about 350 ℃ and the mechanism of solid solu- tion mainly precipitates as needle-like phases during quench sensitive range.

关 键 词：LD7铝合金 时间-温度-转化率(TTT)曲线 时间-温度-性能(TTP)曲线 淬火敏感性 相变动力学 

分 类 号：TG146.21[一般工业技术—材料科学与工程]