Young's modulus of quenched beta Ti-Nb-Sn alloys was investigated as a function of alloy composition. It was found that a minimum of Young's modulus appears at a composition in an unstable beta phase where a thermal omega phase transformation as well as martensitic transformation is almost completely suppressed. Based on this result, quenched beta Ti-Nb-Sn alloys with low Young's modulus were cold-rolled and heat-treated to evolve various micro-structures. Orthorhombic martensite is stress-induced by cold rolling in a Ti-Nb-Sn alloy having Ms just below room temperature. With increasing rolling reduction, the volume fraction of martensite increases and most martensite plates become parallel to the rolling direction. With increasing temperature, reverse martensitic transformation starts above room temperature, proceeds gradually, and finishes at about 250°C, thereby yielding very fine beta-phase grains elongated to the rolling direction. A high density of dislocations and fine alpha precipitates are included in the beta grains. With further increasing temperature the alpha phase precipitation occurs significantly, leading to increases in strength and Young's modulus. Low Young's modulus and high strength are simultaneously attained by controlling the heat treatment condition.
|Number of pages||1|
|Specialist publication||Advanced Materials and Processes|
|Publication status||Published - 2005 Jul 1|
ASJC Scopus subject areas
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering