材料期刊网

本文研究了一种新的热处理工艺——回复再时效(RRA)处理对国产 Al—Zn—Mg—Cu 系 LC9铝合金力学性能和显微组织的影响.结果表明,合金在 T6状态下经220℃5min 加热回复及120℃24h 再时效处理后,在室温拉伸性能不低于 T6状态的同时,获得了高于 T73状态的应力腐蚀抗力.而相应的组织变化则表现为晶粒内部形成大小两种不同尺度范围的沉淀相,使合金具有较高的强度;同时,晶界沉淀物的端部由尖锐变得圆钝,晶界临近区域中的合金元素贫化,使材料的应力腐蚀抗力提高.

The effect of a new heat treatment process,namely,retrogression and reag- ing(RRA),on the mierostructure and properties of A1 alloy LC9 of A1-Zn-Mg-Cu system has been studied.After the alloy of T6 underwent further treatment of 220℃,5 rain retrogression and 120℃,24h reaging,the room temperature tensile properties of the alloy kept no more inferior to that of T6,but such a stress corrosion resistance may be superior to T73 state.The corresponding change in microstrueture of the alloy shows the formation of precipitated phase of two different sizes,both coarse and fine,in the grains,thus,the strength is much improved.Meanwhile,the tip of precipitates along grain boundary becomes obtuse,the alloying elements are depleted in the region near the grain boundary and the stress corrosion resistance is bettered.