X-Ray Measurements of Stacking Faults and Internal Strains in α-Cu-Zn and α-Cu-Sn

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Abstract
Powder‐pattern peaks of cold‐worked and annealed fcc Cu‐Zn and Cu‐Sn filings were measured with a diffractometer using filtered Cu radiation. The plots of the lattice parameter ahkl, calculated from the peak maximum position of the individual (hkl) reflections, as a function of cosθ·cotθ proved to be linear for all annealed powder samples. The large scatter of the individual ahkl values of the cold‐worked filings could be related to the deformation stacking‐fault probability α=α′‐α″ (intrinsic‐fault probability α′ and extrinsic‐fault probability α″), segregation Δx, and internal stresses σ. The lattice parameters (a0)CW of the cold‐worked filings of the Cu‐Zn alloys were larger, whereas (a0)CW of the Cu‐Sn alloys were smaller than the corresponding (a0)Ann values of the annealed filings. The deformation‐fault probability α increases with increasing solute concentration. The combined twin‐fault probabilities β and extrinsic‐fault probability α″, i.e., 4.5 α″+β, were determined from the displacements of the center of gravity from the peak maximum positions of the (111) and (200) reflections. Fourier analysis of the line shapes allowed the determination of the fault probabilities [1.5(α′+α″)+β], the average domain size D, and the rms strain components in the [111] direction. Using the quantities α′‐α″, 4.5 α″+β, and 1.5(α′+α″)+β and solving for α′, α″, and β, no evidence of the occurrence of extrinsic faults in the cold‐worked filings could be found. The values of 1.5 α′+β calculated from line broadening agree rather well with those obtained from lattice‐parameter and center‐of‐gravity changes, indicating that intrinsic deformation and twin stacking faults are the primary causes of the broadening and shifts of the powder‐pattern peaks from cold‐worked α‐Cu‐Zn and α‐Cu‐Sn filings.