Acta Metall Sin  2019, Vol. 55 Issue (6): 709-719    DOI: 10.11900/0412.1961.2018.00430
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Influence of Deformation Parameters on Dynamic Recrystallization of 2195 Al-Li Alloy
Xu LI1,Qingbo YANG1,Xiangze FAN1,Yonglin GUO2,Lin LIN2,Zhiqing ZHANG1,3()
1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
2. Southwest Aluminum Group Co. , Ltd. , Chongqing 401326, China
3. Chongqing Xipeng Industrial Park, Chongqing 401326, China
Abstract

Al-Li alloys have attracted extensive attentions as promising structural materials in aerospace industries due to their excellent mechanical properties, and are usually formed through a variety of hot workings such as rolling and forging. Dynamic recrystallization (DRX) is considered as one of the key microstructure evolutions of Al alloys during hot working, and many works have been done concerning with DRX. However, the influence of deformation parameters on different types of DRX of 2195 Al-Li alloy is still unclear. In this work, hot plane strain compression tests were conducted at the strain rate range from 0.01 s-1 to 1 s-1 and the temperature range from 350 ℃ to 500 ℃ to investigate the critical condition of dynamic recrystallization of 2195 Al-Li alloy under different hot deformation conditions, DRX mechanisms were discussed, and the influence of deformation parameters on different types of DRX was revealed using EBSD and TEM. The results showed that the critical strain decreased with the decrease of Zener-Hollomon parameter (Z), DRX was more sufficient in lower Z value, and discontinuous dynamic recrystallization (DDRX) was primary type while only a little continuous dynamic recrystallization (CDRX) was found. Both CDRX and DDRX were promoted in lower Z value, geometric dynamic recrystallization (GDRX) only occurred in high Z value and increased with further increase of Z value, and the appearance of GDRX was accompanied by the increase of the number of DRX grains so that the DRX fraction slightly increased.

 ZTFLH: TG146.2
Fund: Fundamental Research Funds for the Central Universities(No.106112017CDJQJ328840)
Corresponding Authors:  Zhiqing ZHANG     E-mail:  zqzhang@cqu.edu.cn
 Fig.1  Schematic of observing areas (RD, TD, ND represent rolling, transverse and normal directions, respectively; EBSD—electron backscatter diffraction; TEM—transmission electron microscope) Fig.2  True stress-true strain curves of 2195 Al-Li alloy deformed at the strain rates of $ε˙=0.01?s-1$ (a), $ε˙=0.1?s-1$ (b) and $ε˙=1?s-1$ (c) Fig.3  Curves of θ-σ (a~c) and (d2θ/dσ2)-σ (d) of 2195 Al-Li alloy (θ—work hardening rate, σ—stress, σc—critical stress, σs—saturation stress) Fig.4  σc curves under different deformation parameters (a) and relationship of lnεc-lnZ (b) of 2195 Al-Li alloy (Z—Zener-Hollomon parameter, εc—critical strain) Table 1  lnZ values of 2195 Al-Li alloy under different deformation conditions Fig.5  Electron backscatter diffraction (EBSD) images of 2195 Al-Li alloy deformed at different lnZ (CDRX—continuous dynamic recrystallization, GDRX—geometric dynamic recrystallization, DDRX—discontinuous dynamic recrystallization) Fig.6  Boundary misorientation angle distribution histograms of Fig.5f(a) whole image (b) the zone between dotted lines Fig.7  Volume fraction and average grain size of dynamic recrystallization Fig.8  TEM images of 2195 Al-Li alloy deformed at different lnZ Fig.9  High resolution TEM image of T1 phase