Microstructure evolution and aging behavior of Mg-Zn-Y alloy processed by high pressure torsion

doi:10.13251/j.issn.0254-6051.2021.01.031

Abstract

Abstract: Microstructure evolution and aging behavior of high-pressure torsion (HPT) deformed Mg-Zn-Y alloy were studied by using transmission electron microscope (TEM),scanning electron microscope (SEM),X-ray diffraction (XRD) instrument and microhardness tester. The results show that before and after HPT deformation,the second phase particles in the alloy are W phase and Mg₂₄Y₅ phase,and the formation of any new precipitates is not observed after HPT processing,indicating that HPT deformation does not lead to phase transformation of the alloy.At the same time,it is found that the HPT deformation process is accompanied by the generation of deformation twins and the multiplication of a large number of dislocations.The deformation twins are subdivided by the second phase particles during the HPT process.Compared with undeformed alloys,HPT deformation can accelerate the aging process,that is,reach a relatively high peak hardness under a shorter aging time.The specimens after HPT deformed 7 turns of are aged at 175 ℃ for 8 h,the peak microhardness reaches about 114 HV0.1.After aging treatment,the precipitated phase preferentially nucleates at the dislocations and twin boundary,indicating that dislocations and twin boundary act as preferential nucleation sites for the precipitated phases.

Key words: magnesium alloy, high pressure torsion (HPT), microstructure, precipitated phases, twin

CLC Number:

TG146.2

Wang Jinhui, Yin Xiaoming, Li Yansheng, Qu Cheng, Xu Rui. Microstructure evolution and aging behavior of Mg-Zn-Y alloy processed by high pressure torsion[J]. Heat Treatment of Metals, 2021, 46(1): 167-172.

References

[1] Mordike B L,Ebert T.Magnesium:Properties-applications-potential[J].Materials Science and Engineering A,2001,302(1):37-45.
[2] Sauvage X,Murashkin M Y,Straumal B B,et al.Ultrafine grained structures resulting from SPD-induced phase transformation in Al-Zn alloys[J].Advanced Engineering Materials,2016,17(12):1821-1827.
[3] Edalati K,Akama D,Nishio A,et al.Influence of dislocation-solute atom interactions and stacking fault energy on grain size of single-phase alloys after severe plastic deformation using high-pressure torsion[J].Acta Materialia,2014,69(5):68-77.
[4] Loucif A,Figueiredo R B,Baudin T,et al.Ultrafine grains and the Hall-Petch relationship in an Al-Mg-Si alloy processed by high-pressure torsion[J].Materials Science and Engineering A,2012,532:139-145.
[5] Mohebbi M S,Akbarzadeh A,Kim B H,et al.Analysis of strain rate sensitivity of ultrafine-grained AA1050 by stress relaxation test[J].Metallurgical and Materials Transactions A,2014,45(12):5442-5450.
[6] Sun W T,Qiao X G,Zheng M Y,et al.Altered ageing behaviour of a nanostructured Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy processed by high pressure torsion[J].Acta Materialia,2018,151:260-270.
[7] Robson J D,Paa-Rai C.The interaction of grain refinement and ageing in magnesium-zinc-zirconium (ZK) alloys[J].Acta Materialia,2015,95:10-19.
[8] 尹晓明,冯凯旋,刘瑞,等.高压扭转对 Mg-Zn-Y 合金第二相溶解的影响[J].金属热处理,2018,43(7):99-103.
Yin Xiaoming,Feng Kaixuan,Liu Rui,et al.Effect of high pressure torsion on dissolution of precipitates in Mg-Zn-Y alloy[J].Heat Treatment of Metals,2018,43(7):99-103.
[9] 杨丽娜,冯运莉,王明明.45 钢高压扭转过程中的组织与性能[J].金属热处理,2019,44(4):151-155.
Yang Lina,Feng Yunli,Wang Mingming.Microstructure and properties of 45 steel during high pressure torsion[J].Heat Treatment of Metals,2019,44(4):151-155.
[10] Li Y S,Qu C,Wang J H,et al.Exceptional aging hardening behaviour of nanocrystalline Mg-Y-Nd-Gd-Zr alloy prepared by high pressure torsion[J].Journal of Alloys and Compounds,2020,813:152123.
[11] Yuan Y C,Ma A B,Jiang J H,et al.Mechanical properties and precipitate behavior of Mg-9Al-1Zn alloy processed by equal-channel angular pressing and aging[J].Journal of Alloys and Compounds,2014,594:182-188.
[12] Ye J,Lin X P,Zhao T B,et al.Influence of pre-strain on the aging hardening effect of the Mg-9.02Zn-1.68Y alloy[J].Materials Science and Engineering A,2016,663:49-55.
[13] Starink M J,Cheng X,Yang S.Hardening of pure metals by high-pressure torsion:A physically based model employing volume-averaged defect evolutions[J].Acta Materialia,2013,61(1):183-192.
[14] Sun W T,Xu C,Qiao X G,et al.Evolution of microstructure and mechanical properties of an as-cast Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy processed by high pressure torsion[J].Materials Science and Engineering A,2017,700:312-320.
[15] Toth L S,Gu C.Ultrafine-grain metals by severe plastic deformation[J].Materials Characterization,2014,92(6):1-14.
[16] Qiao X G,Zhao Y W,Gan W M,et al.Hardening mechanism of commercially pure Mg processed by high pressure torsion at room temperature[J].Materials Science and Engineering A,2014,619:95-106.
[17] Zhang J,Gao N,Starink M J.Microstructure development and hardening during high pressure torsion of commercially pure aluminium:Strain reversal experiments and a dislocation based model[J].Materials Science and Engineering A,2011,528 (6):2581-2591.
[18] Kim W J,Chung C S,Ma D S,et al.Optimization of strength and ductility of 2024 Al by equal channel angular pressing (ECAP) and post-ECAP aging[J].Scripta Materialia,2003,49(4):333-338.
[19] Mohamed I F,Yonenaga Y,Lee S,et al.Age hardening and thermal stability of Al-Cu alloy processed by high-pressure torsion[J].Materials Science and Engineering A,2015,627:111-118.
[20] Dogan E,Wang S,Vaughan M W,et al.Dynamic precipitation in Mg-3Al-1Zn alloy during different plastic deformation modes[J].Acta Materialia,2016,116:1-13.
[21] Sun W T,Qiao X G,Zheng M Y,et al.Exceptional grain refinement in a Mg alloy during high pressure torsion due to rare earth containing nanosized precipitates[J].Materials Science and Engineering A,2018,728:115-123.
[22] Xin Y,Wang M,Zhen Z,et al.Strengthening and toughening of magnesium alloy by {1012} extension twins[J].Scripta Materialia,2012,66(1):25-28.
[23] Zhang H,Huang G S,Wang L F,et al.Improved formability of Mg-3Al-1Zn alloy by pre-stretching and annealing[J].Scripta Materialia,2012,67(5):495-498.
[24] Gharghouri M A,Weatherly G C,Embury J D.The interaction of twins and precipitates in a Mg-7.7at.%Al alloy[J].Philosophical Magazine A,1998,78(5):1137-1149.
[25] Tang L L,Zhao Y H,Islamgaliev R K,et al.Microstructure and thermal stability of nanocrystalline Mg-Gd-Y-Zr alloy processed by high pressure torsion[J].Journal of Alloys and Compounds,2017,721:577-585.
[26] Nie J F,Zhu Y M,Liu J Z,et al.Periodic segregation of solute atoms in fully coherent twin boundaries[J].Science,2013,340:957-960.