The Studies on Micro-Structural Defects in Deformed Composite Matrix of Al–Si–Mg and SiC

Abstract

Detailed Fourier line shape analysis has been performed on three different compositions of the composite matrix of Al–Si–Mg and SiC. The alloy composition in wt% is Al–7%Si, 0.35%Mg, 0.14%Fe and traces of copper and titanium (∼0.01%) with SiC varying from 0 to 30 wt% in three steps i.e., 0, 10 and 30 wt%. The line shift analysis has been performed by considering 111, 200, 220, 311 and 222 reflections after estimating their relative shift. Peak asymmetry analysis has been performed considering neighbouring 111 and 200 reflections and Fourier line shape analysis has been performed after considering the multiple orders 111 and 222, 200 and 400 reflections. Combining all these three analyses it has been found that the deformation stacking faults both intrinsic α′ and extrinsic α′′ are absent in this alloy system whereas the deformation twin β has been found to be positive and increases with the increase of SiC concentration. So, like other Al-base alloys this ternary alloy also shows high stacking fault energy, and the addition of SiC introduces deformation twin which increases with its concentration in the deformed lattices.

Studies of lattice imperfections in deformed aluminum-based lithium alloys by X-ray diffraction

“…The value of (␣Ј -␣Љ), obtained from peak-shift analysis, appears to be negligible, as the values are either within the error limit or they are negative. [5,6] The compoundfault parameters (4.5␣Љ ϩ ␤) and (1.5(␣Ј ϩ ␣Љ)ϩ ␤) obtained, respectively, from the peak-asymmetry and line-shape analysis are, however, not negligible.…”

“…The flat diffractometer samples from the filings of both the cold-worked and annealed states for each composition were prepared from the filing after sieving through a 250-mesh screen and by making briquettes of sizes suitable for diffractometry, as was done earlier. [3][4][5][6] The XRD profiles of both the cold-worked and the annealed samples were recorded from 30 to 105 deg by a PHILIPS* *PHILIPS is a trademark of Philips Electronic Instruments Corp., Mahwah, NJ.…”

“…For line-asymmetry and Fourier line-shape analysis from the multiple orders of reflections like 111-222 and 200-400, different truncation ranges on both sides of a profile were taken, as well as the corresponding backgrounds, so that the Fourier coefficients did not show any hook effect and the center of gravity of the profiles remained almost constant. This procedure of the range and background selection was also adopted in earlier analysis of line shape on different aluminum based alloys, [3][4][5][6] as the "hook effect" of Fourier coefficients depends on the range and background of the profiles in a Warren-Averbach line-profile analysis. [10] …”

“…The microstrain can be determined by assuming a Gaussian strain distribution [3][4][5][6]9,10] as [6] The size coefficients , thus, separated from A L (hkl), yield the effective domain size, average domain size (D), domain size in the faulted plane (T ), and compound-fault probability (1.5 (␣Ј ϩ ␣Љ) ϩ ␤), [3,4,9,13] as [7] from the 111-222 pair and [8] from the 200-400 pair. Combining the previous two equations, the compound-fault probability can be determined by [9] The individual values of ␣Ј, ␣Љ, and ␤ can be determined from simultaneous solution of Eqs.…”

“…This investigation of lattice imperfection is also a continuation of our work on the series of Al-based alloys. [3][4][5][6] The X-ray line-profile analysis used in the present analysis is an established technique and is widely applied [7,8,9] for the investigation of lattice imperfections by XRD. The five different Al-based alloys in the fcc phase taken under investigation have nominal compositions, in wt pct, of Al-0.1Zr-0.1Li (alloy I), Al-0.1Zr-0.5Li (alloy II), Al-0.1Zr-1.0Li (alloy III), Al-4.5Mg-1.5Li (alloy IV), and Al-1.1Mg-1.8Li-1.8Cu-0.15Zr (alloy V).…”