Hysteresis in metallic solid solution and intermetallic compound-hydrogen systems

Abstract

In an attempt to understand the hysteresis phenomena better, tests were made on a series of V x Nb 1 − x ( x = 0.1, 0.2, 0.3), (Nb 1 − x Fe x ) 1 − y Cr y ( x, y = 0.15, 0.14 and 0.20, 0.08) and (Nb 1 − x Fe x ) 1 − x Cr x ( x = 0.05, 0.07) solid solution alloys and Zr(Fe x Cr 1 − x ) 2 ( x = 0.55, 0.75) intermetallic compounds. A pronounced hysteresis was observed for all the alloys used. It was seen that, as the temperature increases the hysteresis effect as measured by the ratio ( P f P d ), where P f is the plateau pressure for hydride formation and P d is the plateau pressure for hydride decomposition, decreases. The hysteresis effect was also affected by the number of hydriding/dehydriding cycles. The hysteresis becomes smaller as the number of cycles increases. The hysteresis effect in the solid solution alloys can be explained in terms of the elastic strain energy. The change in hysteresis in the intermetallic compounds upon cycling is explained in terms of attrition (i.e. decreasing particle size) of the Zr(Fe x Cr 1 − x ) 2.