摘要
选用7A85-T74锻造铝合金为实验材料,研究室温至240℃内热暴露5 h后的合金微观组织、拉伸性能及冲击吸收能量,并结合透射电子显微镜分析微观组织对合金力学性能的影响机理。结果表明:在80~240℃热暴露温度范围内,7A85-T74铝合金晶粒尺寸变化不大,但沉淀相随温度升高有显著变化;在120℃以内,随热暴露温度的升高,析出物尺寸、拉伸性能和冲击吸收能量整体变化不大,沉淀强化机制为位错切过析出物和位错绕过析出物的混合机制;随着热暴露温度由120℃升高至240℃,析出物的平均半径由室温下的3.8 nm增加至12.3 nm,析出物由η'相向η相转变,合金的屈服强度和抗拉强度显著下降,较室温分别下降45.7%和33.5%,伸长率、断面收缩率和冲击吸收能量显著升高,沉淀强化机制转变为位错绕过析出物,断裂方式由沿晶断裂和韧窝型穿晶断裂组成的混合断裂转变为韧窝型穿晶断裂。基于沉淀强化理论讨论析出物尺寸对合金强度与冲击吸收能量的影响,理论分析结果与实验结果相符。
7A85-T74 forged aluminum alloy was chosen as the experimental material,and the microstructure,tensile properties and impact energy of the alloy were investigated after 5 h of thermal exposure at room temperature to 240℃.The mechanism of the influence of the microstructure on the mechanical properties of 7A85-T74 aluminum alloy was also analyzed by transmission electron microscopy.The results show that the grain size of 7A85-T74 aluminum alloy does not change much in the temperature range of 80-240℃,but the precipitation phase changes significantly with the increase of temperature.Below 120℃,the precipitate size,tensile properties and impact absorption energy do not change significantly with increasing thermal exposure temperature,and the precipitation strengthening mechanism is a mixture of dislocation cutting precipitates and dislocation bypassing precipitates.With the increase of the thermal exposure temperature from 120℃to 240℃,the precipitate average radius increases from 3.8 nm at room temperature to 12.3 nm,and the precipitate changes fromη'phase toηphase.The yield strength and tensile strength of the alloy decrease significantly by 45.7%and 33.5%respectively compared with that of room temperature and the elongation,reduction of area and impact energy of the alloy increase significantly.The precipitation strengthening mechanism changes to dislocation bypassing precipitates,and the fracture mode changes from mixed fracture consisting of intergranular fracture and dimple transgranular fracture to dimple transgranular fracture.The effect of precipitate size on the strength and impact energy of the alloy discusses based on the precipitation strengthening theory,and the results of the theoretical analysis are consistent with the experimental results.
作者
王浩
赵君文
范军
张海成
黄兴民
韩靖
Hao WANG;Junwen ZHAO;Jun FAN;Haicheng ZHANG;Xingmin HUANG;Jing HAN(School of Materials Science and Engineering,Southwest Jiaotong University,Chengdu 610031,China;CRRC Changchun Rail Car Company Limited,Changchun 130000,China;Deyang Wanhang Die Forging Company Limited,China Second Heavy Machinery Group,Deyang 618000,Sichuan,China)
出处
《材料工程》
EI
CAS
CSCD
北大核心
2023年第9期107-116,共10页
Journal of Materials Engineering
基金
金属材料强度国家重点实验室开放项目(20212317)。
关键词
7A85铝合金
热暴露
微观组织
力学性能
7A85 aluminum alloy
thermal exposure
microstructure
mechanical property
