Effect of α″ martensite on the microstructure and mechanical properties of beta-type Ti–Fe–Ta alloys

• α″ martensite is of importance for the properties of the designed Ti–Fe–Ta alloys.
• All alloys have higher hardness and strength than those of CP-Ti and Ti–6Al–4V.
• Ti–10Fe–10Ta contains the least amount of α″ martensite phase.
• Ti–10Fe–10Ta has the lowest elastic modulus among the desgned alloys.

This work aimed to investigate the effect of Fe and Ta contents on the β → α″ martensitic transformation as well as the microstructure and mechanical properties of the as-cast designed Ti–xFe–yTa (x = 8, 9, 10 wt% and y = 0, 2, 5, 8, 9, 10 wt%) alloys. The microstructure of all alloys substantially consists of β and α″ phases. However, the addition of more Fe and Ta β-stabilizers to Ti–8Fe alloy reduced the likelihood to form α″ martensite during quenching, hence decreasing the volume fraction of α″ phase and finally reaching 3% in Ti–10Fe–10Ta alloy. The microstructural studies results revealed that except for Ti–8Fe and Ti–9Fe–2Ta, all alloys with high Ta content present a dendritic microstructure. It is noteworthy noting that all alloys possess higher Vickers hardness and compressive yield stress values than those of CP-Ti and Ti–6Al–4V. However, Ti–10Fe–10Ta alloy with the least amount of α″ martensite phase and dominant β phase structure exhibits the lowest elastic modulus and highest plasticity. It was concluded that further decrease in modulus of elasticity can be achieved through stabilizing single β phase by designing composition of Ti–Fe–Ta alloy.

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