TECHNICAL PAPER Phase Evolution and Mechanical Properties of Suction Cast Ti–Fe–Co Ternary Alloys Sumanta Samal 1,2 • Swapnil Agarwal 1 • Krishanu Biswas 1 Received: 8 August 2016 / Accepted: 4 July 2017 Ó The Indian Institute of Metals - IIM 2017 Abstract The current work has been undertaken with an aim to investigate the phase evolution and mechanical behaviour of Ti–Fe–Co ternary alloys. Extensive electron microscopic studies have been carried out to identify the phases present in the microstructure of the suction cast Ti– Fe–Co ternary alloys. The SEM micrographs of the investigated Ti–Fe–Co alloys reveal that the microstruc- tures consist of eutectic matrix (L ? (b-Ti) ss ? Ti(Fe,Co) and/or L?(b-Ti) ss ? Ti 2 (Co,Fe)) along with different dendritic phases ((b-Ti) ss or Ti(Fe,Co), Ti 2 (Co,Fe)) depending on concentration of Co. Ti 70 Fe 20 Co 10 and Ti 75 Fe 15 Co 10 alloys show the bimodal eutectics, ((b- Ti) ss ? Ti(Fe,Co)) and ((b-Ti) ss ? Ti 2 (Co,Fe)). The room temperature uniaxial compressive test of the Ti 70 Fe 20 Co 10 ternary alloy exhibits simultaneous improvement in com- pressive strength (*2819 MPa) and plasticity (*8.5%) among the series of investigated Ti–Fe–Co ternary alloys. Fractography of the surface of Ti 70 Fe 20 Co 10 ternary alloy reveals mixed mode of fracture. The significant outcome of the investigated Ti–Fe–Co alloys is that, the plasticity of the alloys can be improved by the development of bimodal eutectics in the microstructure or by incorporating disor- dered dendritic phase. Keywords Suction casting  Ti alloys  Scanning electron microscopy  Mechanical properties  Fractography 1 Introduction In the last several years, Ti-based alloys have received much attention for aerospace, chemical and medical industries due to their outstanding properties such as high strength-to-weight ratio, workability, corrosion resistance and biocompatibility [1–4]. It is reported [5, 6] that the commercial Ti-6Al-4 V alloy shows ultimate tensile strength of *990–1130 MPa and ductility of *4–13%. While it may be possible to further strengthen the Ti-based alloys by incorporating suitable alloying elements or by modifying microstructural features by using novel synthe- sis route. However, a good combination of strength and ductility can be achieved by designing the heterogeneous microstructure in which micron scale primary dendrite is embedded in the nano/ultrafine eutectic matrix. At first, He et al. [7] have developed such heterogeneous microstruc- ture having nano/ultrafine eutectic along with micron sized dendritic phase in Ti–Cu–Ni–Sn–Nb/Ta multicomponent alloys [7–9] by solidification route. They found that these Ti-based multicomponent alloys possess optimum combi- nation of compressive ultimate strength and ductility. Subsequently, there has been considerable research activity on the Ti-based multicomponent alloys such as Ti–Fe–Sn [10–16], Ti–Fe–Co [17–21], Ti–Ta–Ni–Cu–Co [22] alloys with the promise of developing materials with improved mechanical properties in terms of strength and ductility. However, the systematic investigation on the mechanical behaviour of these multicomponent alloys by correlating with microstructure has not been carried out. Electronic supplementary material The online version of this article (doi:10.1007/s12666-017-1174-y) contains supplementary material, which is available to authorized users. & Krishanu Biswas kbiswas@iitk.ac.in 1 Department of Materials Science and Engineering, Indian Institute of Technology Kanpur, Kanpur, UP 208016, India 2 Discipline of Metallurgy Engineering and Materials Science (MEMS), IIT Indore, Indore, MP 453552, India 123 Trans Indian Inst Met DOI 10.1007/s12666-017-1174-y