Variable low-temperature martensitic behavior of alpha-phase uranium

A martensitic transformation in α-phase uranium is a consequence of the observed softening in the shear elastic constant, C', between 2560K and approximately 420K on cooling. The anomalous low-temperature behavior of uranium is due to the variable appearance of the M/sub f/, M/sub s/, A/sub s/, and A/sub f/ temperatures of the uranium martensite. A 9R martensitic structure is postulated for part, if not all, of the temperature range below 36 to 500K. Its presence would explain the evidence for order below approximately 430K and the low latent heat of transformation observed in the transition back to the parent structure. It is suggested that physical property phenomena observed at 80 to 1000K may be due to an order-disorder change in the intermediate distorted premartensitic (or post-martensitic) structure