An x‐ray diffraction study of lattice imperfections in cold‐worked fcc alloys: II. Copper‐gallium (α phase)

摘要

X‐ray diffraction profiles from four compositions of α‐phase Cu‐Ga alloys with solute gallium at 3.40, 6.90, 10.85, and 15.00 at.% were recorded in a Geiger counter x‐ray diffractometer for both cold‐worked and annealed states of the samples. Detailed studies on the recorded profiles considering recent development in the analyses of line shift, line asymmetry, and Fourier line shape have been made in order to evaluate the microstructural parameters. Considerable influence of net stacking‐fault density α (=α′-α″) over the lattice parameter change and long‐range residual stresses in causing the changes in peak positions has been observed when the concentration of solute gallium is increased in the alloy system. An increased presence of intrinsic fault (density α′) over the extrinsic fault (density α″) has been found, while the twin fault (density β) is totally absent in the deformed structure analogous to the silver gallium (I) system. The logarithmic dependence of α with solute concentration X has been satisfactorily explained by the existing semiempirical relations. The values of the dislocation density ρ and also the parameter γ/μ (γ, stacking‐fault energy; μ, shear modulus) have been evaluated and from the latter, the stacking‐fault energy γ for pure copper has further been estimated.