Phase transformations in PuGa 1at.% alloy: Study of whole reversion process following martensitic transformation

Impact of compressive pressure on the phase stability and transformation behaviour of δ-phase stabilised plutonium alloys

“…The reverse phase transformation (b-a 0 phase Table 2 Chemical analysis determined the following primary impurity levels for the Pu-1 at % Ga and Pu-2 at% Ga alloys. a 0 -phase in the Pu-1 at% Ga alloy, but no a 0 -phase was induced in the Pu-2 at% Ga alloy under these conditions [9,13,23]. …”

“…XRD phase studies conducted following low temperature treatment, have demonstrated that for the most part the a 0 -phase formed in a Pu-1 at% Ga alloy, transforms via the indirect path to the b-phase on heating the specimens to temperatures within the b-phase stability range [9]. However, in Pu-2 at% Ga alloys any a 0 -phase formed is reported to revert entirely back to the d-phase [11].…”

“…The b-phase on cooling would revert to an a 0 -phase with cell volumes matching those of a-phase of pure plutonium [9]. This would therefore indicate that gallium diffusion has occurred on heating the "initially" induced a 0 -phase into the b-phase and that the "retained" a 0 -phase formed from this b-phase on cooling, could be more appropriately termed a-phase.…”

“…Several studies, on the formation of a 0 -phase in d-phase stabilised plutonium-gallium alloys, have reported the observation of a metastable intermediate g 0 -phase during d-a 0 phase transformation under applied pressure, which is not observed under low temperature conditions [5][6][7][8][9]. Transformation of d-a 0 phase in Pu-2 at% alloys has been reported to occur at pressures above 300 MPa and a 0 -phase and g 0 -phase have been observed to coexist with the d-phase, on increasing to pressures above 800 MPa [6].…”

“…This is especially the case with regards to the impact of experimental conditions and the limits and strengths of the different analytical techniques used. The stability of the a 0 -phase for a particular alloy composition, appears to be governed by the methods that are used to induce it [1][2][3][4][5][9][10][11][12][13][14]. The a 0 -phase may revert on heating, directly to the d-phase or by following an indirect path via the b-phase and g-phase (of pure plutonium).…”