摘要
The microstructure,mechanical properties and stress corrosion cracking(SCC)of 7136 aluminum alloy under T 6,T 79 and T 74 aging treatments were studied and the effects of microstructure on the mechanical properties and SCC were discussed.The results show that the ultimate tensile strength and yield strength of the aging 7136 alloys follow this sequence from high to low:T 6>T 79>pre-aging>T 74.For 7136 Al alloy after T 6 aging,the average diameter of the precipitates was(5.7±1.7)nm,and the diameter of 60.7%(number fraction)precipitates was 2−6 nm,leading to a good precipitation strengthening.The K_(IC)of T 74-aging alloy is 38.2 MPa·m^(1/2),which is 26.1%more than that of T 6-aging alloy and 17.5%more than that of T 79-aging alloy.The improved fracture toughness in T 74-aging alloy is mainly due to the reduction of the strength difference between intragranular and grain boundary.The SCC resistance of the aging 7136 alloys follows this sequence from high to low:T 79>T 74>T 6.After T 79 aging,the discontinuous grain boundary precipitates and narrow precipitate free zones were obtained in 7136 alloy,which was beneficial to SCC resistance.
本文研究了7136 Al合金T6、T79和T74态的组织、力学性能和应力腐蚀开裂(SCC)之间的关系,讨论了组织对力学性能和腐蚀开裂敏感性的影响。结果表明,7136合金的抗拉强度和屈服强度值由高到低依次为:T6>T79>预时效>T74。7136-T6合金析出相平均直径为(5.7±1.7)nm,直径在2-6 nm的占比为60.7%,具有良好的析出强化效果。7136-T74合金K1/2IC值为38.2 MPa·m,比T6时效高26.1%,比T79时效高17.5%。T74态合金断裂韧性的增加是由于晶内和晶界强度差减小。7136合金耐腐蚀开裂能力由高到低依次为:T79>T74>T6。这是由于7136-T79合金晶界析出相呈不连续分布和窄的无沉淀析出带的共同作用,而有利于增强耐腐蚀开裂能力。
作者
WEI Shi-long
FENG Yan
ZHANG Hui
XU Chun-ting
WU Ying
韦士龙;冯艳;张辉;许春停;吴瑛(School of Materials Science and Engineering,Central South University,Changsha 410083,China;Key Laboratory of Electronic Packaging and Advanced Functional Materials,Changsha 410083,China;The 38 th Institute of China Electronics Technology Group Corporation,Hefei 230088,China)
基金
Project(2017GK2261)supported by the Science and Technology Program of Hunan Province,China
Project(41423040204)supported by National Key Laboratory of Light Weight and High Strength Structural Materials Equipment Pre-research Laboratory Foundation,China。
