An x-ray Fourier line shape analysis in cold-worked hexagonal magnesium base alloys

Abstract

Detailed Fourier line shape analyses considering x-ray diffraction profiles from fault unaffected 10.0, 00.2, 11.0, 20.0, 11.2, and 00.4 reflections and fault affected 10.1, 10.2, 10.3, 20.1, 20.2, 10.4, and 20.3 reflections have been performed on three magnesium base hexagonal alloys used extensively in the aircraft industry. The first of the three alloys (Mg–Al–Mn, Alloy I) had the nominal composition in wt.% of Al-8.3, Mn-0.35, Si-0.2, Cu-0.12, Fe-0.2, and other 0.01; the second alloy (Mg–Zn–Mn, Alloy II) had the nominal composition in wt.% of Zn-4.0, Mn-0.15, Si-0.01, Cu-0.03, Fe-0.01, Zr-0.70, and rare earth elements-1.50; and the last of the alloys (Mg–Zn–Al, Alloy III) had the nominal composition in wt.% of Zn-4.3, Al-0.15, Mn-0.01, Si-0.03, Cu-0.01, Ni-0.005, Zr-0.6, and rare earth-1.4. The microstructural parameters determined in these analyses indicated the average domain size in alloys I, II, and III as 208 Å, 314 Å, and 400 Å, respectively. The deformation fault densities, α, in these alloy systems (∼54 ⊠ 10⁻³, 35 ⊠ 10⁻³, and 28 ⊠ 10⁻³, respectively, in alloys I, II, and III) were found to be appreciably high compared to the earlier work on pure magnesium (0.63 ⊠ 10⁻³). The deformation twin fault density, β, which was found to be negligible in pure magnesium (∼0.21 ⊠ 10⁻³), was found to be negative here, also indicating the negligible presence of twin faults in these alloys. These results establish that on cold work the solutes introduce deformation stacking faults in an appreciable quantity in magnesium which is not normally susceptible to faulting when in pure form. Of these three alloys, however, Alloy I (Mg–Al–Mn) was found to be the most prone to deformation faulting.