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nd for metallic implant biomaterials in clinical applications has increased rapidly with the growing elderly population.[1] Recently, b titanium (Ti) alloys have attracted increasing attention because of their biological safety, outstanding biocompatibility, and low Young’s modulus.[2] However, the low plasticity and poor wear resistance of Ti alloys relative to Co-Cr alloys restrict their wide application. In addition, porous Ti alloys must consider all mechanical factors including Young’s modulus, strength, plasticity, and wear resistance. Interdiffusion is a critical to the production of homogeneous b Ti alloys,[3–5] and the diffusivity information is essential to obtain biomedical alloys with super-plastic behavior.[6] In general, materials with high hardness have excellent wear resistance and good strength. Therefore, Young’s modulus, interdiffusivity

WEIMIN CHEN, DAHAI ZENG, PAN REN, and WEI LI are with the Institute of Advanced Wear & Corrosion Resistant and Functional Materials, Jinan University, Guangzhou, 510632, Guangdong, P.R. China. Contact e-mails: chenweiming126@jnu. edu.cn, [email protected] BIAO HU is with the School of Materials Science and Engineering, Anhui University of Science and Technology, Huainan 232001, Anhui, P.R. China. Manuscript submitted October 9, 2018.

METALLURGICAL AND MATERIALS TRANSACTIONS A

and hardness are the three major parameters which aid in selecting bio-Ti alloys with excellent properties.[5,7] Scandium (Sc) is a non-toxicity and low-density element that can refine the microstructure and enlarge the b-phase region of Ti alloys. A small amount of Sc has positive effects on the strength and oxidation resistance of cast Ti alloys,[8] and Ti alloys with Sc additive can obtain a high shape-memory property.[9] Considering the advantages of Sc, Ti-rich Ti-Sc system is selected as the topic of this study, the objective of which is to explore experimentally the binary interdiffusivity, Young’s modulus and hardness in targeted bcc Ti-rich Ti-Sc alloys. First, three solid diffusion couples of a bcc Ti-Sc system at 1273 K, 1373 K, and 1473 K are experimentally prepared and measured using electron probe micro-analysis (EPMA). Then, the binary interdiffusivities in bcc Ti-Sc alloys at 1273 K, 1373 K, and 1473 K are determined using the Boltzmann–Matano method.[10] Finally, the composition-dependent Young’s modulus and hardness of the bcc Ti-Sc system are determined through nanoindention measurements based on Oliver–Pharr analysis.[11] Ti (purity: 99.995 wt pct) slugs and Ti (purity: 99.99 wt pct) cubes purchased from Alfa Aesar (China) Chemicals Co., Ltd. and Sc (purity: 99.9 wt pct) ingot from Shanghai Aladdin Bio-Chem Technology Co., LTD were used as starting materials. Three binary Ti-6.85, 6.68 and 7.60 at. pct Sc alloys were prepared by arc melting under an Ar atmosphere using a non-reactive electrode (WKDHL-1, Opto-electronics Co., Ltd., Beijing, China). The buttons and pure Ti cubes were linearly cut into blocks of 8 9 8 9 2 mm3, and were ground using SiC papers. They were then