Origin of unusual fracture in stirred zone for friction stir welded 2198-T8 Al-Li alloy joints

IMR OpenIR

	Origin of unusual fracture in stirred zone for friction stir welded 2198-T8 Al-Li alloy joints
	Tao, Y.; Ni, D. R.; Xiao, B. L.; Ma, Z. Y.; Wu, W.; Zhang, R. X.; Zeng, Y. S.; Ni, DR (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China.; Zeng, YS (reprint author), AVIC Beijing Aeronaut Mfg Technol Res Inst, Beijing 100024, Peoples R China.
	2017-05-02
发表期刊	MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
ISSN	0921-5093
卷号	693 页码:1-13
摘要	Friction stir welded (FSW) joints of conventional precipitation-hardened aluminum alloys usually fracture in the lowest hardness zone (LHZ) during tension testing. However, all of the FSW joints of a 2198-T8 Al-Li alloy fractured in the stirred zone (SZ) instead of the LHZ with the welding parameters of 800 rpm-200 mm/min and 1600 rpm-200 mm/min under the condition that no welding defects existed in the SZ. The experiment results revealed that lazy S was not the dominant factor resulting in the unusual fracture. The SZ consisted of three subzones, i.e., the shoulder-affected zone, the pin-affected zone, and the transition zone between them. While the former two zones were characterized by fine and equiaxed recrystallized grains, incompletely dynamically recrystallized microstructure containing coarse elongated non-recrystallized grains was observed in the transition zone. The transition zone exhibited the lowest average Taylor factor in the SZ, resulting in a region that was crystallographically weak. Furthermore, obvious lithium segregation at grain boundaries was observed in the transition zone via time-of-flight secondary ion mass spectroscopy analysis, but not in the shoulder affected zone or the pin-affected zone. The combined actions of both the two factors resulted in the appearance of preferential intergranular fracture in the transition zone and eventually caused the failure in the SZ. The lithium segregation at grain boundaries in the transition zone was closely associated with both the segregation in the base material and the partially dynamically recrystallized microstructure resulting from the inhomogeneous plastic deformation in the SZ.; Friction stir welded (FSW) joints of conventional precipitation-hardened aluminum alloys usually fracture in the lowest hardness zone (LHZ) during tension testing. However, all of the FSW joints of a 2198-T8 Al-Li alloy fractured in the stirred zone (SZ) instead of the LHZ with the welding parameters of 800 rpm-200 mm/min and 1600 rpm-200 mm/min under the condition that no welding defects existed in the SZ. The experiment results revealed that lazy S was not the dominant factor resulting in the unusual fracture. The SZ consisted of three subzones, i.e., the shoulder-affected zone, the pin-affected zone, and the transition zone between them. While the former two zones were characterized by fine and equiaxed recrystallized grains, incompletely dynamically recrystallized microstructure containing coarse elongated non-recrystallized grains was observed in the transition zone. The transition zone exhibited the lowest average Taylor factor in the SZ, resulting in a region that was crystallographically weak. Furthermore, obvious lithium segregation at grain boundaries was observed in the transition zone via time-of-flight secondary ion mass spectroscopy analysis, but not in the shoulder affected zone or the pin-affected zone. The combined actions of both the two factors resulted in the appearance of preferential intergranular fracture in the transition zone and eventually caused the failure in the SZ. The lithium segregation at grain boundaries in the transition zone was closely associated with both the segregation in the base material and the partially dynamically recrystallized microstructure resulting from the inhomogeneous plastic deformation in the SZ.
部门归属	[tao, y. ; ni, d. r. ; xiao, b. l. ; ma, z. y.] chinese acad sci, inst met res, shenyang natl lab mat sci, shenyang 110016, peoples r china ; [tao, y.] univ chinese acad sci, beijing 100049, peoples r china ; [wu, w. ; zhang, r. x. ; zeng, y. s.] avic beijing aeronaut mfg technol res inst, beijing 100024, peoples r china
关键词	Friction Stir Welding Aluminum-lithium Alloys Microstructure Fracture Behavior
学科领域	Nanoscience & Nanotechnology ; Materials Science, Multidisciplinary ; Metallurgy & Metallurgical Engineering
资助者	National Natural Science Foundation of China [51331008]
收录类别	SCI
语种	英语
WOS记录号	WOS:000401384400001
引用统计	被引频次：51[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
条目标识符	http://ir.imr.ac.cn/handle/321006/78147
专题	中国科学院金属研究所
通讯作者	Ni, DR (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China.; Zeng, YS (reprint author), AVIC Beijing Aeronaut Mfg Technol Res Inst, Beijing 100024, Peoples R China.
推荐引用方式 GB/T 7714	Tao, Y.,Ni, D. R.,Xiao, B. L.,et al. Origin of unusual fracture in stirred zone for friction stir welded 2198-T8 Al-Li alloy joints[J]. MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING,2017,693:1-13.
APA	Tao, Y..,Ni, D. R..,Xiao, B. L..,Ma, Z. Y..,Wu, W..,...&Zeng, YS .(2017).Origin of unusual fracture in stirred zone for friction stir welded 2198-T8 Al-Li alloy joints.MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING,693,1-13.
MLA	Tao, Y.,et al."Origin of unusual fracture in stirred zone for friction stir welded 2198-T8 Al-Li alloy joints".MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 693(2017):1-13.