分级淬火对7N65铝合金微观组织和断裂韧性的影响  

Effect of Interrupted Quenching on Microstructure and Fracture Toughness of 7N65 Aluminum Alloy

作　　者：林立健 张勇[1] 郑许 唐建国[1,3] LIN Lijian;ZHANG Yong;ZHENG Xu;TANG Jianguo(School of Materials Science and Engineering,Central South University,Changsha 410083,Hunan,China;Guangxi Key Laboratory of Materials and Processes of Aluminum Alloys,ALG Aluminum Inc,Nanning 530031,Guangxi,China;Key Laboratory of Nonferrous Metallic Materials Science and Engineering,Ministry of Education,Central South University,Changsha 410083,Hunan,China)

机构地区：[1]中南大学材料科学与工程学院,湖南长沙410083 [2]广西南南铝加工有限公司广西铝合金材料与加工重点实验室,广西南宁530031 [3]中南大学有色金属材料科学与工程教育部重点实验室,湖南长沙410083

出　　处：《矿冶工程》2023年第5期149-153,158,共6页Mining and Metallurgical Engineering

基　　金：国家重点研发计划(2022YFB3403701);广西科技重大专项(桂科AA22068075)。

摘　　要：通过分级淬火实验研究了7N65合金在不同保温温度与不同保温时间下的硬度(HV)和单位裂纹形核功(UIE)变化,绘制了合金的TTP-HV曲线及TTP-UIE曲线。结合扫描电镜、透射电镜等表征方法,对不同温度下的第二相析出行为进行了研究。结果表明,高温(390~450℃)保温时,晶界析出相以S(Al_(2)CuMg)相为主,随着保温时间延长,其尺寸与数量增大,合金断裂韧性下降,断裂方式为沿扁平晶粒断开的脆性断裂;低温(250~390℃)保温时,晶界析出相以η(MgZn_(2))相为主,随着保温时间延长,晶界特征变化不大,晶内η相数量增加、尺寸增大,导致晶内强度降低,晶内-晶界强度差减小,合金断裂韧性上升,断裂方式为穿晶断裂。Interrupted quenching experiments were conducted to investigate the hardness(HV)and unit initiation energy(UIE)of 7N65 alloy samples at various temperatures with different hold time,and the relative TTP⁃HV and TTP⁃UIE contour diagrams were also plotted.The precipitation behavior of second phases at various temperatures was characterized by adopting scanning electron microscope and transmission electron microscope.The findings reveal that S⁃phase(Al_(2)CuMg)is the dominant grain boundary precipitate after the alloy is held at a temperature between 390℃and 450℃,and increases in grain size and numbers as hold time is prolonged.Thus the alloy has less fracture toughness and is prone to fragile fracture along with the broken grains.When the alloy sample is held at a temperature between 250℃and 390℃,precipitates at grain boundaries are predominated byη⁃phase(MgZn_(2)),which increases in the numbers and grain size as hold time is prolonged,leading to lower strength of inner grain,smaller difference in strength between inner grains and grain boundaries.Thus,the alloy has higher fracture toughness and is more prone to ductile fracture with more transgranular dimples.

关 键 词：7N65合金 分级淬火 断裂韧性 铝合金 固溶处理 时效 裂纹形核功 TTP曲线 

分 类 号：TG156[金属学及工艺—热处理]