Effect of alpha ' Martensite on Microstructure Refinement After alpha plus beta Isothermal Treatment in a Near-alpha Titanium Alloy Ti60

摘要

The effect of the alpha' martensite on microstructure refinement after alpha + beta isothermal treatment in a near-alpha titanium alloy Ti60 was investigated. A high density of the refined acicular alpha plates nucleate and grow inside alpha' martensite during the isothermal treatment. The refinement mechanism of the alpha' martensite was determined by comparing the direct beta to alpha and alpha' to alpha phase transformations. The alpha phase prefers to nucleate along the grain boundaries during the beta -> alpha transformation. However, in the alpha' martensite, the refinement of the alpha phase is attributed to the precipitation of a small amount of beta phase in between the adjacent alpha phase, and the stacking faults inside the alpha' martensite. In addition, the yield strength and elongation of the alloy both increase due to the refinement of the alpha phase.