Effect of step-quenching on microstructure of aluminum alloy 7055  

作　　者：刘胜胆 张勇 刘文军 邓运来 张新明 

机构地区：[1]School of Materials Science and Engineering, Central South University [2]Key Laboratory of Nonferrous Materials, Ministry of Education, Central South University

出　　处：《中国有色金属学会会刊：英文版》2010年第1期1-6,共6页Transactions of Nonferrous Metals Society of China

基　　金：Project(2005CB623706) supported by the National Basic Research Program of China

摘　　要：The effect of step-quenching on the microstructure of aluminum alloy 7055 after artificial aging was studied by hardness testing and transmission electron microscopy (TEM). Step-quenching leads to decomposition of solid solution and heterogeneous precipitation of equilibrium phase mainly on dispersoids and at grain boundaries; thus lower hardness after aging. Prolonging isothermal holding at 415 ℃ results in coarser and more spaced η phase particles at grain boundaries with wider precipitates free zone, and lower density of larger η′ hardening precipitates inside grains after aging. Isothermal holding at 355 ℃ results in heterogeneous precipitation of η phase both on dispersoids and at grain boundaries. Isothermal holding at 235 ℃ results in heterogeneous precipitation of η phase first, and then S phase. Precipitates free zones are created around these coarse η and S phase particles after aging. Prolonging isothermal holding at these two temperatures leads to fewer η′ hardening precipitates inside grains, larger and more spaced η phase particles at grain boundaries and wider grain boundary precipitates free zone after aging.The effect of step-quenching on the microstructure of aluminum alloy 7055 after artificial aging was studied by hardness testing and transmission electron microscopy （TEM）. Step-quenching leads to decomposition of solid solution and heterogeneous precipitation of equilibrium phase mainly on dispersoids and at grain boundaries; thus lower hardness after aging. Prolonging isothermal holding at 415 ℃ results in coarser and more spaced ηphase particles at grain boundaries with wider precipitates free zone, and lower density of larger η＇ hardening precipitates inside grains after aging. Isothermal holding at 355 ℃ results in heterogeneous precipitation of η phase both on dispersoids and at grain boundaries. Isothermal holding at 235 ℃ results in heterogeneous precipitation of ηphase first, and then S phase. Precipitates free zones are created around these coarse ηand S phase particles after aging. Prolonging isothermal holding at these two temperatures leads to fewer η＇ hardening precipitates inside grains, larger and more spaced ηphase particles at grain boundaries and wider grain boundary precipitates free zone after aging.

关 键 词：7055铝合金 显微组织 非均相沉淀 phase 透射电子显微镜 晶界析出 硬度测试 沉淀硬化 

分 类 号：TG146.21[一般工业技术—材料科学与工程] TB333[金属学及工艺—金属材料]