The solubility of hydrogen was determined at about 700 to 1250K in the austenitic phases of TiNi0.8Cu0.2 and TiNi0.6Cu0.4 shape memory alloys having hydrogen contents ≤ 0.048. The solubility was found to obey Sieverts law and to decrease with increasing copper content. The values of the partial molar enthalpy and partial molar non-configurational entropy of solution per mole of hydrogen were: ΔHH0 = -28kJ/mol; ΔSHnc = -80J/molK (TiNi0.8Cu0.2) ΔHH0 = -31kJ/mol; ΔSHnc = -88J/molK (TiNi0.6Cu0.4). The chemical diffusion coefficient Dc  of H was determined for the TiNi0.8Cu0.2 alloy by fitting the isothermal pressure versus time absorption curves to a relationship derived from Fick's second law. The data for Dc were in good agreement with those of the Einstein diffusion coefficient DE previously determined by the Snoek anelastic relaxation peak due to hydrogen. The H diffusivity in TiNi0.8Cu0.2 could be described by:

D(m2/s) = 3 x 10-7exp[-0.53(eV)/kT]

A comparison of the present results with those available for other Ni-Ti-Cu alloy compositions revealed a gradual decrease in Dc with increasing copper content from x = 0 to x = 0.4.

Solubility and Diffusion of Hydrogen in TiNi1-xCux (x = 0.2 and 0.4) Shape Memory Alloys. G.Mazzolai: Journal of Alloys and Compounds, 2007, 446-447, 204-7