Microstructure and Mechanics Property Variations during MDIF of Ti-6Al-4V Alloy with a Martensitic Microstructure

doi:10.3969/j.issn.1004-132X.2021.22.011

Abstract

Abstract: The as-cast Ti-6Al-4V alloy was subjected to a heat treatment condition to obtain a typical α′ martensitic microstructure. After two-step isothermal forging, a homogeneous equiaxed grained microstructure with an average grain size of 1.5 μm was achieved. The refined microstructure led to a significant mechanics property improvement. The fine grained Ti-6Al-4V alloys exhibited high yield strength(906 MPa), high ultimate tensile strength(954 MPa), and good ductility(16.7%). The finer grain size and better mechanics properties indicate that the phase transformation of α′/α+β strongly contributed to the microstructure refinement during isothermal forging of Ti-6Al-4V alloys. After the first step forging, the microstructure near the center of the forging is highly deformed, while very little deformations are present in the center regions near the die due to the effects of die chilling and friction. After the second step forging, α lamellae are fully globularized and the microstructure is homogeneous. The crystal rotations of the grains near the center are larger than that of the grains in the midway from the center to the outer edge.

Key words: multidirectional isothermal forging (MDIF), Ti-6Al-4V alloy, martensite, grain refinement, mechanics properties

摘要： 将铸态Ti-6Al-4V钛合金经过β相区热处理水淬之后获得马氏体组织，经过两步多向等温锻造之后获得了平均晶粒尺寸为1.5 μm的均匀等轴细晶组织，其室温拉伸屈服强度为906 MPa，抗拉强度为954 MPa，伸长率为16.7%，相比铸态Ti-6Al-4V钛合金，其室温力学性能得到了极大提升。研究表明，获得马氏体组织对钛合金晶粒细化有着巨大促进作用。第一步等温锻造之后的钛合金坯料组织并不均匀，存在变形区和“变形死区”，在变形区域内，心部位置应变量最大，组织细化最为明显，从心部到两端应变量逐渐减小，片层组织变形量相应减小；经过90°换向后的第二步等温锻造之后，钛合金坯料组织内的片层组织基本全部细化，形成了均匀的等轴晶组织，从心部到两端，随着应变量的减小，晶粒取向变化相应减小。

关键词: 多向等温锻造, Ti-6Al-4V钛合金, 马氏体, 晶粒细化, 力学性能

CLC Number:

TH142.2

ZHANG Zhixiong, ZHANG Juntao, HAN Jianchao, ZHANG Changjiang, ZHANG Shuzhi, WANG Tao, . Microstructure and Mechanics Property Variations during MDIF of Ti-6Al-4V Alloy with a Martensitic Microstructure[J]. China Mechanical Engineering, 2021, 32(22): 2739-2748.

张志雄, 章俊涛, 韩建超, 张长江, 张树, 王涛. 马氏体组织Ti-6Al-4V钛合金多向等温锻造组织演变及力学性能强化研究[J]. 中国机械工程, 2021, 32(22): 2739-2748.

References

［1］孙佳, 李学雄, 张金虎, 等. Ti-6Al-4V合金β→α相变中晶界α相形成机制的相场模拟［J］. 金属学报, 2020, 56(8)：1113-1122.
SUN Jia, LI Xuexiong, ZHANG Jinhu, et al. Phase Field Simulation of the Formation Mechanism of Grain Boundary α Phase in Ti-6Al-4V Alloy β→α Phase Transition［J］. Acta Metallurgica Sinica, 2020, 56(8)：1113-1122.
［2］杜子杰, 李文渊, 刘建荣, 等, CMT增材制造TC4-DT合金组织均匀性与力学性能一致性研究［J］. 金属学报，2020, 56(12)：1667-1680.
DU Zijie, LI Wenyuan, LIU Jianrong, et al. Research on the Uniformity and Mechanical Properties of CMT Additive Manufacturing TC4-DT Alloy［J］. Acta Metallurgica Sinica, 2020, 56(12)：1667-1680.
［3］GAO P F, FU M W, ZHAN M, et al. Deformation Behavior and Microstructure Evolution of Titanium Alloys with Lamellar Microstructure in Hot Working Process:a Review ［J］.Journal of Materials Science & Technology, 2020, 39：56-73.
［4］ZHANG W J, DING H, PEREIRA P H R, et al. Grain Refinement and Superplastic Flow in a Fully Lamellar Ti-6Al-4V Alloy Processed by High-pressure Torsion ［J］.Materials Science and Engineering：A, 2018, 732：398-405.
［5］ZHANG Z X, QU S J, FENG A H, et al. Hot Deformation Behavior of Ti-6Al-4V Alloy：Effect of Initial Microstructure ［J］.Journal of Alloys and Compounds, 2017, 718：170-181.
［6］SHENG J W, WANG Z Y, ZHENG L H, et al. Characterization of Microstructure and Texture Evolution in Ti664 Titanium Alloy after Multidirectional Forging and Annealing Treatments ［J］.Journal of the Minerals, Metals & Materials Society, 2019, 71(12)：4687-4695.
［7］ZHANG Z X, QU S J, FENG A H, et al.The Low Strain Rate Response of As-cast Ti-6Al-4V Alloy with an Initial Coarse Lamellar Structure ［J］.Metals, 2018, 8(4)：1-13.
［8］KUMAR P, PRAKASH O, RAMAMURTY U. Micro-and Meso-structures and Their Influence on Mechanical Properties of Selectively Laser Melted Ti-6Al-4V ［J］.Acta Materialia, 2018, 154：246-260.
［9］JOVANOVIC＇ M T, TADIC＇ S, ZEC S, et al. The Effect of Annealing Temperatures and Cooling Rates on Microstructure and Mechanical Properties of Investment Cast Ti-6Al-4V Alloy ［J］. Materials and Design, 2006, 27(3)：192-199.
［10］SESHACHARYULU T, MEDEIROS S C, FRAZIER W G, et al. Microstructural Mechanisms during Hot Working of Commercial Grade Ti-6Al-4V with Lamellar Starting Structure ［J］. Materials Science and Engineering：A, 2002, 325(1/2)：112-125.
［11］ZHANG Z X, QU S J, FENG A H, et al. Microstructural Mechanisms during Multidirectional Isothermal Forging of As-cast Ti-6Al-4V Alloy with an Initial Lamellar Microstructure ［J］. Journal of Alloys and Compounds, 2019, 773：277-287.
［12］BELADI H, CHAO Q, ROHRER G S.Variant Selection and Intervariant Crystallographic Planes Distribution in Martensite in a Ti-6Al-4V Alloy ［J］. Acta Materialia, 2014, 80：478-489.
［13］WARWICK J L W, JONES N G, BANTOUNAS I, et al. In Situ Observation of Texture and Microstructure Evolution during Rolling and Globularization of Ti-6Al-4V ［J］. Acta Materialia, 2013, 61(5)：1603-1615.
［14］PRAKASH D G L, HONNIBALL P, RUGG D, et al. The Effect of β Phase on Microstructure and Texture Evolution during Thermomechanical Processing of α+β Ti Alloy ［J］. Acta Materialia, 2013, 61(9)：3200-3213.
［15］OBASI G C, MOAT R J, PRAKASH D G L, et al. In Situ Neutron Diffraction Study of Texture Evolution and Variant Selection during the α→β→α Phase Transformation in Ti-6Al-4V ［J］. Acta Materialia, 2012, 60(20)：7169-7182.
［16］ZHANG C J, GUO C X, ZHANG S Z, et al. Microstructural Manipulation and Improved Mechanical Properties of a Near Α Titanium Alloy ［J］. Materials Science and Engineering：A, 2020, 771：138569.
［17］薛克敏, 郭威威, 时迎宾, 等, TA15钛合金多向锻压组织和拉伸性能研究［J］. 稀有金属材料与工程 2019, 48(10)：3340-3345.
XUE Kemin, GUO Weiwei, SHI Yingbin, et al. Research on Multi-directional Forging Microstructure and Tensile Properties of TA15 Titanium Alloy ［J］. Rare Metal Materials and Engineering 2019, 48(10)：3340-3345.
［18］陶国强,祁广源,曲寿江,等.多向等温锻造Ti-44Al-4Nb-1.5Cr-0.5Mo-0.1B-0.1Y合金高温压缩变形行为研究［J］. 钛工业进展，2018, 35(3) :11-15.
TAO Guoqiang, QI Guangyuan, QU Shoujiang, et al. Research on High Temperature Compression Deformation Behavior of Multi-directional Isothermal Forging Ti-44Al-4Nb-1.5Cr-0.5Mo-0.1B-0.1Y Alloy［J］. Progress in Titanium Industry 2018, 35(3)：11-15.
［19］张阳,邵建波,陈韬,等. Mg-5.6Gd-0.8Zn合金多向锻造过程中的变形机制及动态再结晶［J］. 金属学报, 2020, 56(5)：723-735.
ZHANG Yang, SHAO Jianbo, CHEN Tao, et al. Deformation Mechanism and Dynamic Recrystallization of Mg-5.6Gd-0.8Zn Alloy during Multi-directional Forging Process ［J］. Acta Metallurgica Sinica, 2020, 56(5)：723-735.
［20］纪小虎, 李萍, 时迎宾, 等, TA15钛合金等温多向锻造晶粒细化机理与力学性能［J］. 中国有色金属学报,2019, 29(11)：2515-2523.
JI Xiaohu, LI Ping, SHI Yingbin, et al. Grain Refinement Mechanism and Mechanical Properties of TA15 Titanium Alloy Isothermal Multi-directional Forging ［J］. The Chinese Journal of Nonferrous Metals, 2019, 29(11)：2515-2523.
［21］ZHEREBTSOV S V, SALISHCHEV G A, GALEYEV R M, et al. Production of Submicrocrystalline Structure in Large-scale Ti-6Al-4V Billet by Warm Severe Deformation Processing ［J］. Scripta Materialia, 2004, 51(12)：1147-1151.
［22］XU W, BRANDT M, SUN S, et al. Additive Manufacturing of Strong and Ductile Ti-6Al-4V by Selective Laser Melting via in Situ Martensite Decomposition ［J］. Acta Materialia, 2015, 85：74-84.
［23］BIELER T R, SEMIATIN S L. The Origins of Heterogeneous Deformation during Primary Hot Working of Ti-6Al-4V ［J］. International Journal of Plasticity, 2002, 18(9)：1165-1189.
［24］CAO S, CHU R K, ZHOU X G, et al. Role of Martensite Decomposition in Tensile Properties of Selective Laser Melted Ti-6Al-4V ［J］. Journal of Alloys and Compounds, 2018, 744：357-363.
［25］CHAO Q, HODGSON P D, BELADI H. Microstructure and Texture Evolution during Symmetric and Asymmetric Rolling of a Martensitic Ti-6Al-4V Alloy ［J］. Metallurgical and Materials Transactions A, 2016, 47(1)：531-545.

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