Mechanically-Induced Phase Transformations in Plutonium Alloys

Abstract

AbstractIn this article, we show that mechanically-induced phase transformations can be readily achieved in two Pu-alloy systems. We have observed mechanically-induced phase transformations in both Ti-stabilized β-Pu and Ga-stabilized δ-Pu, In both of these alloys, the parent phase has been largely transformed to α-Pu, and the cause of these transformations was mechanical strain introduced by the metallographic sample preparation. For the Ga alloys, x-ray diffraction (XRD) patterns were taken at about 1.5-μm steps down to the undisturbed material in order to develop depth profiles of the surface damage. The total depth of the disturbed material in these alloys is estimated to be about 7.6μm, but this depth was not measured for the Ti alloys. The proportions of α-Pu and δ-Pu in the Ga alloys have been estimated using (a) a new quantitative phase analysis program (SPECQUAN) that uses multiple peaks of each phase in order to minimize the effects of preferred orientation and (b) an older manual technique (i.e., hand calculations). The results from these techniques are compared. SPECQUAN was developed to use the Specplot data file structure directly, thus reducing our data processing. The program is written in Fortran 77 and employs an external intensity ratio quantification procedure to obtain its results. XRD calibration has been done independently by means of accurate density measurements on a reference Ga alloy.