Phase transformations in hafnium alloys are of interest as a means of achieving a material which exhibits flow softening and high localized strains during deformation at high strain rates. Hafnium transforms from a body-centered-cubic beta phase to a hexagonal alpha phase upon cooling below 1749 deg C. Hafnium-based alloys containing up to 17.5percent Ti, up to 17.5percent Ta, and up to 7.3percent Zr by weight were button-arc melted and, in some cases, hot extruded to obtain a refined grain size. A number of alloys were shown to have beta solvus temperatures in the range of 1100 to 1300 deg C and showed evidence of a shear transformation upon water quenching. The Vickers microhardness of the quenched materials are typically above 350 HV as compared to 300 HV or less for materials with an alpha plus beta structure. Quenching dilatometry indicates a martensite start temperature of about 750 deg C for the Hf-7.5 Ta-10 Ti-1 Zr alloy and 800 deg C or more for the Hf-7.5 Ta-7.5 Ti-1 Zr alloy. Tensile tests at 1 s~(-1) strain rate show a constant ultimate tensile strenght for temperatures up to 600 deg C for the above two alloys and a rapid decrease in strength with a further increase in temperature.
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