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In this study, a TiNbCrTa refractory complex concentrated alloy (RCCA) was prepared using vacuum arc remelting. The microstructural evolution and mechanical properties of both as-cast and heat-treated RCCA samples were analyzed. Heat treatment (HT) was performed at 800–1200 °C for 1 h in a vacuum-sealed environment. These samples exhibited a formation of Cr2Nb and Cr2Ti Laves phases. A variation in elemental distribution was observed, with interdendritic (ID) regions showing higher fractions of Ti and Cr, while the dendritic regions had a greater concentration of Ta and Nb. Micro-segregation at the IDs was confirmed through energy dispersive x-ray spectroscopy mapping, which inferred the formation of Cr- and Ti-rich phases during HT at 800–1200 °C. High-temperature HT at 1200 °C for 1 h led to the evolution of the hcp omega phase. Prolonged HT at 1200 °C for 96 h resulted in the evolution of a Cr-rich Laves phase (Cr2Ta), which was homogeneously distributed within the microstructure, indicating an unstable microstructure. Furthermore, despite prolonged HT, a variation in the elemental distribution persisted due to the presence of dendritic and ID regions. Electron backscattered diffraction analysis revealed the presence of bcc and hcp phases in the dendritic and ID regions, respectively, of the as-cast and HTed samples. The as-cast samples demonstrated a high compressive strength of approximately 2 GPa. Micro-hardness values increased with the HT temperature up to 1000 °C. Further increases under HT conditions did not significantly reduce the microhardness value, whereas prolonged HT at 1200 °C led to an increase in the microhardness value. Overall, the newly developed TiNbCrTa RCCA exhibited high-strength behavior even after the phase transformation. [ABSTRACT FROM AUTHOR]

Herein, the development of directional solidification for a novel high‐temperature Mo–20Si–52.8Ti (at%) ternary alloy using a modified Bridgeman type apparatus is presented. The resulting alloy exhibits a microstructure consisting of a body‐centered cubic solid solution (BCCss) and a hexagonal silicide (Ti,Mo)5Si3 with approximate volume fractions of 50% for each phase. The phases exhibit a crystallographic orientation relationship with (123)BCCSS||(0001)(Ti,Mo)5Si3$\left(\left(\right. 123 \left.\right)\right)_{\left(\text{BCC}\right)_{\text{SS}}} \left|\right. \left|\right. \left(\left(\right. 0001 \left.\right)\right)_{\left(\left(\right. \text{Ti} , \text{Mo} \left.\right)\right)_{5} \left(\text{Si}\right)_{3}}$ and [111¯]BCCSS||[112¯0](Ti,Mo)5Si3$\left(\left[\right. 11 \bar{1} \left]\right.\right)_{\left(\text{BCC}\right)_{\text{SS}}} \left|\right. \left|\right. \left(\left[\right. 11 \bar{2} 0 \left]\right.\right)_{\left(\left(\right. \text{Ti} , \text{Mo} \left.\right)\right)_{5} \left(\text{Si}\right)_{3}}$. Different solidification velocities are imposed, which reveal an inverse relationship to the lamellar spacing according to a Jackson–Hunt type scaling. Mechanical characterization using Vickers indentation demonstrates that the BCCss accommodates plasticity through dislocation motion, while the silicide phase exhibits high hardness and brittleness, serving as a crack initiation site. Crack propagation is arrested and deflected at the interface to the BCCss. Fracture toughness measurements via indentation yield a fracture toughness of 3.7 MPa√m for the silicide, somewhat higher than previously reported values for Nb‐, Mo‐, and Cr‐based silicides at room temperature. The directionally solidified specimens show an enhanced fracture toughness attributed to a greater BCCss length scale; thus, combining the ductile and hard phases results in a ductile‐phase toughened intermetallic composite. The findings open up new possibilities for the design of advanced intermetallic composites with improved toughness performance. [ABSTRACT FROM AUTHOR]

This work aimed to manufacture Ti–28.5Nb and Ti–40.0Nb (wt%) alloys in situ via selective laser melting (SLM) from Ti and Nb elemental powders. X-ray diffraction analysis revealed complete β-phase (cubic) in Ti–40.0Nb and a mixture of (α′′ orthorhombic + β cubic) phases in Ti–28.5Nb were formed, whereas few of the Nb particles remained only partially fused during manufacturing. The fraction of partially melted Nb particles was determined as ∼2 and ∼18% in Ti–28.5Nb and Ti–40Nb, respectively. Mechanical characterization revealed higher hardness and more strength in Ti–28.5Nb than in Ti–40.0Nb due to the presence of the α′′ phase in the former. Tribocorrosion tests reveal a significantly better wear-corrosion resistance for Ti–40.0Nb, as determined from a lower total volume loss in Ti–40.0Nb (∼2 × 10−4 mm−3) than in Ti–28.5Nb (∼13 × 10−2 mm−3). The lower volume loss and better corrosion resistance behavior are attributed to the β phase, which was dominant in Ti–40.0Nb. Cell studies reveal no toxicity for up to 7 days. Both the alloys were better at supporting cell proliferation than wrought Ti6Al4V. This study presents a route to preparing Ti–Nb alloys in situ by SLM that are promising candidates for biomedical applications. [ABSTRACT FROM AUTHOR]