Stress and temperature dependence of stress relaxation ageing behaviour of an Al-Zn-Mg alloy

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:773

Article

Lyu, Fenggong^1,4,5  Li, Yong²  Shi, Zhusheng³  Huang, Xia^1,4,5  Zeng, Yuansong^1,4,5  Lin, Jianguo³ 

[1] AVIC Mfg Technol Inst, Beijing 100024, Peoples R China

[2] Beihang Univ, Sch Mech Engn & Automat, Beijing 100191, Peoples R China

[3] Imperial Coll London, Dept Mech Engn, London SW7 2AZ, England

[4] Aeronaut Key Lab Plast Forming Technol, Beijing 100024, Peoples R China

[5] Beijing Key Lab Digital Plastic Forming & Equipme, Beijing 100024, Peoples R China

关键词: Stress relaxation;    Ageing;    Al-Zn-Mg alloy;    AA7B04;    Precipitation;    Creep age forming;   

DOI  :  10.1016/j.msea.2019.138859

来源: Elsevier

【 摘 要 】

y The stress (from elastic to plastic) and temperature dependence of stress relaxation ageing (SRA) behaviour of an Al-Zn-Mg alloy, AA7B04-P, has been experimentally investigated in this study. A series of SRA tests have been carried out under various initial stress levels in both elastic and plastic regions and at different temperatures. Corresponding microstructural evolution during SRA has been characterised using transmission electron microscopy (TEM). It is found that increasing the initial stress and/or temperature enhance the stress relaxation in both elastic and plastic regions. The dislocation creep mechanism plays the dominant role at the investigated temperatures during SRA, with the stress exponent n ranging from 3 to 8, decreasing with increasing temperature. External stresses accelerate the coarsening of GP zones and eta' precipitates and, when loaded to the plastic region, promote the formation of large rod-shaped eta precipitates within 2 h of SRA tests, due to the high energy sites provided by dislocations from plastic loading. Yield strength shows a much higher sensitivity to the temperature than creep strain has during SRA tests. A temperature below 165 degrees C is suggested for SRA of AA7B04-P, so that a high stress relaxation level with less than 15% strength loss can be obtained after 16 h forming.

【 授权许可】

Free