Effect of Grain Size on the Shear Banding Behavior of Ti-6Al-4V Alloy Under Quasi-Static Compression
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INTRODUCTION
TI-6AL-4V alloy is a representative a + b titanium alloy widely employed in aerospace, military, chemical, and biomedical applications because of its attractive properties such as low density, high specific strength, good corrosion resistance, and outstanding biocompatibility.[1,2] It is well known that ultrafine-grained (ufg) and nanocrystalline (nc) materials possess excellent mechanical properties.[3] A variety of ufg or nc titanium alloys have been fabricated by means of equal channel angular pressing (ECAP), high pressure torsion (HPT), forging, and powder metallurgy.[4–7] The titanium alloys with fine grain size usually exhibit higher strength relative to their coarse-grained (cg) counterparts. As to coarse-grained Ti-6Al-4V alloy, most researches on deformation and fracture mechanisms have been carried out in cast alloys. A number of dislocations and
YAN LONG and HAIYAN PENG are with the Guangdong Provincial Key Laboratory for Processing and Forming of Advanced Metallic Materials, School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, P.R. China. Contact e-mail: [email protected] LIANG PENG, WEIHUA ZHANG and JINFU ZHANG are with the National Near-Net-Shape Forming Engineering Research Center for Metallic Materials, South China University of Technology, Guangzhou 510640, P.R. China. XIAOLONG HUANG is with the Xiamen Golden Egret Special Alloy Co., Ltd., Xiamen 361006, P.R. China. Manuscript submitted May 09, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
twins, which have distinct effects on mechanical properties, emerge in cast Ti-6Al-4V alloy during the deformation process.[8,9] Bridier et al.[10] investigated slip systems of Ti-6Al-4V alloy and proved the coexistence of basal, prismatic, and first-order pyramidal slip modes. Besides, the flow stress of Ti-6Al-4V alloy is sensitive to the temperature and strain rate, and the adiabatic shear band is the main failure mode of the Ti-6Al-4V alloy at elevated temperature and/or high strain rates.[11] In ufg and nc titanium alloys, shear bands were also observed under dynamic loading condition.[12] Obviously, the formation of shear bands played an important role in the plastic deformation and failure process of titanium alloys. Since the mechanical performance of Ti-6Al-4V is strongly sensitive to its microstructure, it is important to clarify the deformation modes in fine-grained Ti-6Al-4V and the relationship between the grain size, mechanical behavior, and properties. In this work, fine-grained Ti-6Al-4V alloys were prepared by high-energy ball milling (HEBM) and spark plasma sintering (SPS). The shear banding behaviors under quasi-static compression were observed and the effect of average grain size on the mechanical behaviors of Ti-6Al-4V alloy was also investigated.
II.
MATERIALS AND METHODS
Spherical Ti-6Al-4V alloy powders produced by means of plasma rotating electrode atomization were used as initial materials. The impurity content of
atomized powders was 0.018 pct C, 0.100 pct O, 0.020 pct
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