The effects of deformation and the transition of microstructural defect states with the interchange of solvent and solute in Ti–Zr and Zr–Ti alloys of six different compositions and Zr–Sn alloys in three different compositions have been investigated by X-ray diffraction line profile analysis. The detailed analysis of the X-ray powder diffraction line profiles was interpreted by Fourier line shape analysis using modified Rietveld method and Warren–Averbach method taking silicon as standard. Finally the microstructural parameters such as coherent domain size, microstrains within domains, faulting probability and dislocation density were evaluated from the analysis of X-ray powder diffraction data of Zr base Sn, Ti and Ti base Zr alloys by modified Rietveld powder structure refinement. This analysis confirms that the growth fault, 𝛽, is totally absent or negligibly present in Zr–Ti, Ti–Zr and Zr–Sn alloy systems, because the growth fault, 𝛽, has been observed to be either negative or very small for these alloy systems. This analysis also revealed that the deformation fault, 𝛼, has significant presence in titanium-base zirconium alloy systems but when zirconium content in the matrix goes on increasing beyond 50%, this faulting behaviour suffers a drastic transition and faulting tendency abruptly drops to a level of negligible presence or zero. This tendency has also been observed in Zr–Sn alloys signifying high stacking fault energy. Therefore, Zr and Zr-base alloys having high stacking fault energy can be used as hard alloys in nuclear technology at high temperature.