Microstructural
and fatigue crack growth behaviorinhomogeneity of trace Sc
added 7085 alloy friction stir welded joint
Zixing Jia2,
Lili Wei1,2,11∗Corresponding author 1. Tel.: +86 13517739930. E-mail address:hhfwll@163.com. (Lili Wei),
Hongfeng
Huang1,2,22∗Corresponding author 2. Tel.: +86 13517738716. E-mail address:csuworld@163.com.(Hongfeng
Huang), Chongyu Liu2, Hongjie
Jiang2, Xuda Xu3
1 Key Laboratory of
New Processing Technology for Nonferrous Metal & Materials, Guilin
University of Technology, Ministry of Education, Guilin 541004, China
2 College of Materials Science and Engineering,
Guilin University of Technology,
Guilin 541004, China
3 Sanshui
Fenglv
Aluminium Co., Ltd., Foshan, 528000, China
Abstract
The
inhomogeneity of friction stir weld (FSW) joint of a 7085 Al-based alloy
containing trace Sc was investigated by comparing the hardening phase
morphology, grain structure, mechanical properties and fatigue crack
growth (FCG) behavior in based metal (BM), heat-affected zone (HAZ) and
weld nugget zone (WNZ). The results showed that microstructural
evolution during FSW was remarkably affected by Sc addition. The
recrystallization and growth of grains in BM and HAZ were restrained by
coherent Al3(Sc,Zr) particles.
In HAZ, partially dissolution and
slight growth of precipitates resulted in softening but contributed to
enhance the FCG resistance according to shear mechanism. In WNZ, high
frictional heating and intense plastic deformation induced
recrystallization and supersaturated solid solution which decomposed to
form new reprecipitates, including many new GPII zones, 𝜂′ phases and
some coarse 𝜂 equilibrium phases attached to grown incoherent
Al3(Sc,Zr). Owing to combined influences of fine random
orientated grain structure and reprecipitates, WNZ possessed the best
fatigue endurance.
Keywords:Aluminum
alloy; Friction stir welding; Fatigue crack growth; Mechanical
properties.