Djamel Bradai

Grain growth in AZ31 alloy after uniaxial compression

The grain growth morphology, kinetics and texture change after uniaxial compression at 430 °C of an extruded AZ31 alloy were studied. The samples were loaded following two routes insuring two initial textures of the samples with compression direction parallel and normal to the extrusion direction. For both initial textures, a stable grain size is attained upon isothermal annealing and the grain growth kinetics can be described by: dn = dnR + kt with an n value of around 15. The annealing texture with grown grains is a retained hot deformation texture without emerging or strengthening other components. Abnormal grain growth is not observed for annealing time up to 10 000 h at 450 °C.

X-ray diffraction analysis of cold-worked Cu-Ni-Si and Cu-Ni-Si-Cr alloys by Rietveld method

Abstract Cold worked and annealed supersaturated Cu-2.65Ni-0.6Si and Cu-2.35Ni-0.6Si-0.6Cr alloys were studied. The microstructural parameters evolution, including crystallite size, root mean square strain and dislocation density was analyzed using Materials Analysis Using Diffraction software (MAUD). The parameters for both alloys have typical values of cold deformed and subsequently annealed copper based alloy. A net change of the crystallite size, root mean square strain and dislocation density values of the alloys aged at 450 °C for 2.5–3 h seems corresponding to the recovery and recrystallization processes. Addition of Cr as quaternary element did not lead to any drastic changes of post deformation or ageing microstructural parameters and hence of recovery-recrystallization kinetics.

X-ray peak profile analysis of dislocation type, density and crystallite size distribution in cold deformed Pb-Ca-Sn alloys

Abstract The density, nature of the dislocations and distribution of the domain sizes in cold-deformed Pb-Ca-Sn solid solution were determined by X-ray diffraction profile analysis. The dislocation densities are of the order of 10 10 cm −2 . The strain broadening of diffraction profiles was accounted for by dislocation contrast factor. The coherent domain size was determined by the recently developed PM2K software package. Assuming that the domain size distribution is log-normal, the distribution function (median μ and variance σ) was calculated from the size parameters determined from X-ray diffraction profile analysis.

DSC analysis of commercial Cu–Cr–Zr alloy processed by equal channel angular pressing

Abstract Samples of a commercial Cu–1Cr–0.1Zr (mass fraction, %) alloy were subjected to equal channel angular pressing (ECAP) up to 16 passes at room temperature following route Bc. Differential scanning calorimetry (DSC) was used to highlight the precipitation sequence and to calculate the stored energy, recrystallization temperature and activation energy after each ECAP pass. On another hand, electrical properties were correlated with the dislocation density. Results show that the stored energy increases upon increasing ECAP pass numbers, while the recrystallization temperature decreases significantly.

On the texture and grain growth in hot-deformed and annealed WE54 alloy

Abstract A WE54 (Mg–Y–Nd–Zr) magnesium alloy was subjected to uniaxial and plane strain compression at two temperatures (300 and 400°C) and two strain rates (10–4 and 10–2 s–1). This processing resulted in a relative weakening of the initial strong basal texture of the as-received material. Contrarily to the conventional AZ31 alloy, the deformation texture was more or less insensitive to the processing parameters but depended strongly on the hot deformation type. Annealing treatments at 450°C up to 7 days resulted in normal grain growth. The grain growth annealing caused dissolution of the precipitates that had developed during hot deformation at 300°C. The grain growth kinetics can be described by Dn = DRn + kt, where n was found to range between 6 and 11. A net randomization of the texture was evidenced for all the deformation conditions.

Texture and Microstructure of WE54 Alloy after Hot Rolling and Annealing

The texture and microstructure after hot rolling and annealing of WE54 alloy was investigated using X-ray techniques and optical microscopy. WE54 alloy was hot rolled at 400°C to two different reductions (20% and 53%) and then annealed at 450°C for 30 minutes. These treatments resulted in a retained but much weaker basal texture with grain size almost unchanged.

Grain boundary character distribution of CuNiSi and FeNi alloys processed by severe plastic deformation

In this work the Grain Boundary Character Distribution (GBCD) in general and the relative proportion of low-Σ CSL (Coincidence Site Lattice) grain boundaries are determined through EBSD in Cu-2.5Ni-0.6Si (wt.%) and Fe-36Ni (wt.%) alloys after processing by high-pressure torsion, equal- channel angular pressing and accumulative roll bonding.

Microstructure and Microtexture Evolution of Invar Alloy after Cross Accumulative Roll Bonding (CARB) Compared to ARB

The microstructure and microtexture evolution of a Fe-36%Ni alloy processed by cross accumulative roll-bonding was investigated using Electron BackScatter Diffraction. Deformation led to the development of elongated ultrafine grains parallel to the rolling direction that subsequently became more equiaxed. The grains were more effectivelly refined after CARB than after ARB processing. The grain aspect ratio (l/L) decreased (which means a trend towards elongated sub-grain structure) after 2 and 3 CARB processing cycles and then increased (which means a trend towards equiaxed subgrain structure) from 4 to 5 cycles. The fraction of HAGB, CSL boundaries and the estimated deformed volume fraction gradually increased with increasing number of CARB cycles. Copper-type texture was observed after CARB odd cycles (RD//RD), while after even cycles (RD//TD) a new texture component named H ({012}<221>) was observed.

Investigation of texture, microstructure, and mechanical properties of a magnesium–lanthanum alloy after thermo-mechanical processing

Abstract The texture, microstructure, and mechanical properties of Mg-1.33La (wt.%) alloy after hot rolling and cold plane strain compression were investigated by using X-ray diffraction, optical microscopy, and micro-hardness measurements. This thermo-mechanical processing resulted in a relative weakening of the texture that was mainly a basal type. The microstructures after hot rolling and cold plane strain compression revealed the presence of a second phase (Mg17La2), mostly at grain boundaries. Twins were profuse, and their morphologies were quite different after hot rolling and cold plane strain compression. The Mg-1.33La (wt.%) alloy exhibited good room temperature formability and an increase in strength. The alloys hardness increased with increasing deformation strain. Such properties were explained by the effect of both the Mg17La2 phase precipitation and the samples texture.

Characterization of the deformation texture after tensile test and cold rolling of a Ti-6Al-4V sheet alloy

The deformation texture after cold rolling and tensile test of an industrial Ti-6Al-4V sheet alloy was studied using X-ray diffraction. The alloy was subjected to a cold rolling to different thickness reductions (from 20% to 60%) and then tensile tests have been carried out along three directions relatively to the rolling direction (0°, 45° and 90°). The experimental results were compared to the existing literature and discussed in terms of active plastic deformation mechanisms.