Advanced nanostructured equiaxed Ti-6Al-4V alloys prepared via an isothermal hydrogenation process

Advanced nanostructured equiaxed Ti-6Al-4V (Ti64) alloys were developed via an isothermal hydrogenation process (IHP). The starting equiaxed Ti64 was modified through IHP conducted with hydrogen loadings in the range 0.3-0.7 H/M at 600 degrees C. Microstructural characterizations by optical microscopy, scanning electron microscopy, and X-ray diffraction revealed that only the micrometer-sized alpha matrices of the initial equiaxed Ti64 sample were selectively refined by IHP to form nanostructural platelets with a thickness of 50-150 nm. The submicrometer-sized beta grains of the initial sample did not change. Mechanical test results revealed that the inhomogeneous microstructure of the dehydrogenated specimen caused by the introduction of temporary beta(H) phase containing a hydrogen loading of 0.6 H/M exhibited the best compressive mechanical properties. This specimen was characterized by increasing the compressive yield stress by a factor of 1.40, up to 1223 MPa, and by reducing the compressive failure elongation by a factor of 0.25, down to 24%, compared to the starting equiaxed specimen. By comparing the above results with those observed in the starting lamellar Ti64 treated with similar IHP conditions reported previously, the development of the advanced nanostructured equiaxed Ti64 via IHP could be closely controlled by the shape of the alpha and beta grains in the Ti64, the hydrogen loading, and the types of titanium hydride present, beta(H) and delta. (C) 2015 Elsevier B.V. All rights reserved.