Heterogeneous duplex structured Ti–Sn–Mo alloys with high strength and large plastic deformability

• Formation of heterogeneous duplex structure in Ti–Sn alloy by addition of Mo.
• The heterogeneous duplex structure containing β-Ti solid solution phase encapsulated by ultrafine-scale α-Ti/Ti3Sn lamellar phases.
• Enhancement of both strength up to ∼1 GPa and large plastic strain of ∼30%.

We report that the formation of the heterogeneous duplex structure and its influence on the mechanical properties in Ti–Sn–Mo alloys by optimization of the Mo concentration ratio. With the addition of Mo up to 5 at.%, the colony size and the alternating lamellar phase thickness are significantly decreased and the solid state phase transformation of supersaturated β-Ti to α-Ti phases is strongly suppressed. The unique heterogeneous duplex structure, which is micrometer-scale supersaturated β-Ti solid solution phase are encapsulated by ultrafine-scale α-Ti/Ti3Sn lamellar phases along the β-Ti phase boundary areas, effectively releases the stress concentration and hampers the excessive strain localization during deformation, leading to a high strength of ∼1 GPa and a large plastic strain of ∼30%.