Post-Dynamic Softening of Austenite in a Ni-30%Fe Model Alloy After Hot Deformation

doi:10.11900/0412.1961.2019.00310

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	Post-Dynamic Softening of Austenite in a Ni-30%Fe Model Alloy After Hot Deformation
	Chen Wenxiong 1,2; Hu Baojia 1,2; Jia Chunni 1,2; Zheng Chengwu 1,2; Li Dianzhong 1,2
刊名	ACTA METALLURGICA SINICA
	2020-06-01
卷号	56 期号:6 页码:874-884
关键词	Ni-30%Fe austenitic model alloy hot deformation sub-structure restoration post-dynamic recrystallization austenite
ISSN号	0412-1961
DOI	10.11900/0412.1961.2019.00310
通讯作者	Zheng Chengwu(cwzheng@imr.ac.cn)
英文摘要	Multi-pass processing is commonly used in hot working of steels. Dynamic recrystallization (DRX) occurs during hot deformation, while post-dynamic softening takes place during the inter-pass times and post-deformation annealing. Three different mechanisms are believed to be responsible for the post-dynamic softening stage. These are static recovery (SRV), static recrystallization (SRX), and postdynamic recrystallization (P-DRX). Each of these mechanisms can change the microstructure of austenite (i.e. grain size and distribution). As a result, the post-dynamic softening behavior of austenite may play an important role in the microstructures and the final mechanical properties of the steel product. In this work, a Ni-30%Fe model alloy is used to study softening of austenite in post-deformation annealing after the hot deformation at 900 degrees C and strain rate 0.001 s(-1). The microstructures in the annealed samples carefully analyzed by EBSD in conjunction with TEM. The results show that P-DRX and sub-structural restoration are believed to be responsible for softening of the material after hot deformations. The P-DRX generally consumes deformed structures by the growth of the preformed nuclei of dynamic recrystallization. The sub-structural restoration in austenite usually takes place through the dislocation climb, leading to sub-boundary disintegrations and dislocation annihilations. When the sample is deformed to the peak strain, the deformation microstructure is composed of both recrystallized grains and deformed matrix. The large gradient of stored energy between the recrystallized grains and deformed matrix effectively promotes the strain-induced migration of the large-angle grain boundaries, which makes the P-DRX become the predominated post-dynamic softening mechanism during the post-deformation annealing. Meanwhile, the sub-boundaries within the deformed matrix gradually disintegrate through the restoration mechanism, which also contributes to the post-dynamic softening of austenite. On the other hand, the dislocation annihilation can result in a reduction of the stored energy within the deformation matrix, which inhibits the further migration of grain boundaries. In contrast, when the sample is deformed to the steady-state stage of the dynamic recrystallization, a fully recrystallized microstructure is obtained. The sub-structural restoration process of the fully recrystallized microstructure is much faster than that in the deformed matrix during the post-deformation annealing. It makes the sub-structural restoration become the predominated post-dynamic softening mechanism of this alloy in the steady-state condition. Furthermore, the disintegration of large numbers of sub-boundaries leads to an increase of the dislocation density in local region around the grain boundaries, which facilitates local migration of the high-angle grain boundaries and accelerates the softening of the material.
资助项目	National Natural Science Foundation of China[51771192] ; National Natural Science Foundation of China[51371169] ; National Natural Science Foundation of China[51401214]
WOS研究方向	Metallurgy & Metallurgical Engineering
语种	英语
出版者	SCIENCE PRESS
WOS记录号	WOS:000546975500008
资助机构	National Natural Science Foundation of China
内容类型	期刊论文
源URL	[http://ir.imr.ac.cn/handle/321006/139638]
专题	金属研究所_中国科学院金属研究所
通讯作者	Zheng Chengwu
作者单位	1.Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China 2.Univ Sci & Technol China, Sch Mat Sci & Engn, Shenyang 110016, Peoples R China
推荐引用方式 GB/T 7714	Chen Wenxiong,Hu Baojia,Jia Chunni,et al. Post-Dynamic Softening of Austenite in a Ni-30%Fe Model Alloy After Hot Deformation[J]. ACTA METALLURGICA SINICA,2020,56(6):874-884.
APA	Chen Wenxiong,Hu Baojia,Jia Chunni,Zheng Chengwu,&Li Dianzhong.(2020).Post-Dynamic Softening of Austenite in a Ni-30%Fe Model Alloy After Hot Deformation.ACTA METALLURGICA SINICA,56(6),874-884.
MLA	Chen Wenxiong,et al."Post-Dynamic Softening of Austenite in a Ni-30%Fe Model Alloy After Hot Deformation".ACTA METALLURGICA SINICA 56.6(2020):874-884.