Investigation of a→w transformation in the Zr‐Hf system to 42 GPa

Structural transformations in pure Zr and Hf and their alloys with 5.2, 21.1, 42.9, and 71.3 at . % Hf have been investigated up to 42 GPa (1 GPa = 10 kbar) at room temperature (∼22 °C) by in situ high‐pressure x‐ray diffraction techniques, using a diamond‐anvil pressure cell. The pressure of transformation a→w increases rapidly with increasing Hf content. On extrapolation, the pressure of transformation a→w for Hf is estimated to be in the order of 60 GPa. Values of the c0/a0 ratio of the pressure‐induced w phase for Zr and its alloys are 0.621±0.002, in good agreement with those of heat‐treated w phases in the Zr‐Nb system.