Microstructure and properties of beta TieNb alloy prepared by powder metallurgy route using titanium hydride powder Bhupendra Sharma a, * , Sanjay Kumar Vajpai b , Kei Ameyama a a Department of Mechanical Engineering, College of Science and Engineering, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu-city, Shiga 525-8577, Japan b Research Organization of Science and Technology, Ritsumeikan University,1-1-1 Noji-Higashi, Kusatsu-city, Shiga 525-8577, Japan article info Article history: Received 29 July 2015 Received in revised form 25 September 2015 Accepted 6 October 2015 Available online 14 October 2015 Keywords: Titanium hydride Mechanical alloying Spark plasma sintering Beta-titanium alloys TieNb alloys abstract In the present work, Tie40 mass%Nb alloys were successfully fabricated by a powder metallurgy route consisting of mechanical alloying (MA) of TiH 2 eNb powder mixture and spark plasma sintering (SPS). The use of brittle TiH 2 powder, instead of ductile elemental powder, led to significant increment in the yield of mechanically alloyed (MAed) powder. The MAed powder consisted of homogeneously distrib- uted nano-sized Ti/Nb hydride particles together with micron-sized pure Nb particles. The MA also led to the lowering of dehydrogenation temperature of hydride particles. Sintering of MAed powders under low temperature conditions (1223 K, & 1373 K) resulted in the fine-grained heterogeneous microstructure consisting of a, b, and unreacted pure Nb phase. On the other hand, sintering at higher temperatures (1523 K) resulted in a relatively coarse-grained chemically homogeneous microstructure with almost complete b phase. Coarse-grained homogeneous b TieNb alloy exhibited higher average hardness as compared to that of heterogeneous fine grained microstructures. An attempt has been made to illustrate the correlation between the microstructural characteristics and mechanical properties of the sintered Ti e40Nb compacts. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Titanium and its alloys have been widely used in key engi- neering applications covering a variety of areas, such as aerospace, marine, biomaterials, chemical industries, sports, etc., due to their unique combination of outstanding mechanical and chemical properties [1,2]. In spite of all the meritorious properties of titanium-based alloys, the complexities associated with their thermo-mechanical processing and subsequent machining limit their widespread usage [3,4]. Therefore, it is necessary to develop an optimum fabrication/processing strategy to offer commercially viable and good quality Ti-based near-net shaped products. A powder metallurgy based processing approach could be a suitable way of achieving these objectives. However, the preparation and handling of Ti-based powders has several issues associated with it. Nevertheless, in recent years, several new processes have been developed to prepare high quality elemental Ti and Ti-alloys at a relatively lower cost [5e11]. These processes combined with other secondary powder metallurgy based operations offer several ad- vantages over other conventional fabrication processes, enhancing the feasibility of commercial viability of Titanium and its alloys. Since powder metallurgy has near-net shape processing capabil- ities, i.e. minimizing post fabrication machining, it is even more suitable for the fabrication of fine grained titanium-based alloy components with controlled density and microstructure [12,13]. The powder metallurgy processes based on mechanical alloying (MA) of elemental powders followed by hot consolidation have emerged as a promising method of preparing a wide range of metals and alloys with fine-grained microstructure and excellent mechanical properties. Furthermore, this approach is also very effective in preparing complex alloy systems wherein various alloying elements have a wide difference in their melting points; thus, difficult to prepare through conventional liquid metallurgy route. Therefore, it is envisaged that powder metallurgy could be a promising method of preparing a variety of titanium-based alloy systems wherein such issues exist very often. However, pure tita- nium powder has very high tendency to agglomerate and stick with * Corresponding author. Department of Mechanical Engineering, Ritsumeikan University, Biwako Kusatsu Campus, 1-1-1 Noji-Higashi, Kusatsu-city, Shiga 525- 8577, Japan. E-mail address: gr0185fx@ed.ritsumei.ac.jp (B. Sharma). Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom http://dx.doi.org/10.1016/j.jallcom.2015.10.053 0925-8388/© 2015 Elsevier B.V. All rights reserved. Journal of Alloys and Compounds 656 (2016) 978e986