ARTICLES Microstructure and texture evolution in Mg–Al–Zn–(AgIn) alloy during single and multiple pass warm rolling (original) (raw)
Related papers
Key Engineering Materials, 2018
In the present investigation the rolling response, microstructure and texture evolution of four Mg alloys during multi-pass warm rolling were evaluated. The nominal composition of the base alloy (alloy-1) was Mg-3Al-1Zn. The alloy-2, 3 and 4 were developed by separate additions of non-rare earth elements Ag and In, and a master alloy 85Ag15In (wt.%) to make target compositions Mg-3Al-1Zn-0.5x, (x = Ag ,In, AgIn). Samples from all four alloys were subjected to multi-pass warm rolling at 300 °C to accumulative reductions of 50, 75 and 90% with 8 minutes inter-pass annealing. For all four alloys, crack free sheets of less than 1 mm thickness were produced successfully with true strain corresponding to 90% reduction. The as-cast microstructures revealed second phase particles at grain boundaries and grains interiors for all alloys. A slight scatter in the size of the deformed grains was observed for alloy-1, 2 and 3 after rolling reductions of 50, 75 and 90%. However, a sustained decrea...
Materials Science and Engineering: A, 2012
The microstructure and texture evolution during hot rolling (350 • C) and subsequent annealing are compared in Mg-2.9Y and Mg-2.9Zn (in wt%) solid solution alloys. It is shown that Y in solid solution, unlike Zn, suppresses dynamic recrystallization. Nevertheless, the two alloys exhibit similar, strong basal textures. Upon isothermal annealing of the rolled material at 400 • C, the texture is weakened only in the Mg-2.9Y alloy. The texture weakening is attributed to static recrystallization in basal parent grains. During rolling of Mg-2.9Y, basal parent grains store a high amount of basal dislocations that are organized in a very fine substructure. Such a highly energetic configuration gives rise to fine recrystallized grains with a wide orientation spread during annealing. On the other hand, off-basal parent grains with c-axes close to the RD-TD plane develop coarser substructure accommodating prismatic slip during rolling. The energy stored in these grains is significantly lower than that in basal ones (∼20 times smaller). Static recrystallization at off-basal parent grains leads to coarse new grains and involves rotations about caxis. The texture weakening induced by static recrystallization in Mg-2.9Y was found to result in higher ductility and lower anisotropy when compared to Mg-2.9Zn.
Materials Science and Engineering: A, 2008
The combined effects of lithium additions (1-3 wt%) and processing parameters (rolling temperature, annealing) on the microstructural and texture evolution of pure Mg and Mg-3 wt% Al-1 wt% Zn alloy have been studied. Following rolling the basal planes were aligned with the sheet surface, although the basal poles were split and rotated towards the rolling direction. Lithium additions increased the rotation of basal poles in the rolling and transverse directions; an increase in the rolling temperature was associated with decreased rotation in the rolling direction and some broadening of texture in the transverse direction. Recrystallization during rolling varied between alloys, but had little influence on the texture. Recrystallization, and particularly grain growth, during annealing resulted in a single peak in the basal poles replacing the split observed following rolling. Texture is interpreted in terms of deformation, recrystallization and grain growth. Microstructural and texture evolution during industrial forming processes are also discussed.
Microstructural evolution during recrystallization of magnesium alloys
2012
Microstructural evolution during the annealing of cold rolled Mg, Mg-1.5Nd and Mg-3Y sheets has been examined. The experimental results show a significant difference in recrystallization kinetics and grain growth between pure Mg and Mg-RE alloy sheets. Pure Mg sheet shows rapid recrystallization and grain growth, whereas recrystallization is considerably retarded in the Mg-RE alloys. Although recrystallized grains which are triggered at shear bands in the cold rolled pure Mg sheet show a relatively weak texture with a basal pole split into the sheet rolling direction, rapid grain growth is accompanied by re-strengthening of the basal-type texture. In contrast, a weak texture appears in the early recrystallization stage in Mg-RE alloys and is retained during annealing due to retarded recrystallization and grain growth.
Microstructure and Texture Evolution During Annealing of Caliber Rolled Mg–3Al–1Zn Alloy
Mg–3Al–1Zn (AZ31) alloy was caliber rolled isothermally at the temperature of 300 °C to develop fine grains of 3 lm size. The microstructure and texture evolution of caliber rolled bar during annealing at 300 °C was investigated for 5 to 6000 min. The grain growth from 6 to 17 lm was observed. The grain growth was noted to be faster initially but it became sluggish after *60 min of annealing. The changes in pole figure intensity, mis-orientation angle, kernel average mis-orientation and grain orientation spread were observed after caliber rolling and after annealing. The microstructure and presence of twins after caliber rolling play a vital role in formation of texture after annealing. The changes in microstructure and texture were analysed and the mechanisms involved are discussed.
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing, 2012
In the present study, asymmetric rolling was carried out for incorporating a shear component during the rolling at different temperatures, and was compared with conventional (symmetric) rolling. The microstructures were investigated using electron back-scatter diffraction (EBSD). The strain incorporated was compared with the help of grain orientation spread (GOS). GOS was eventually used as a criterion to partition the microstructure for separating the deformed and the dynamically recrystallized (DRX) grains. The texture of the partitioned DRX grains was shifted by ∼30 • along the c-axis from the deformed grains. The mechanism of dynamic recrystallization (DRX) has been identified as continuous dynamic recovery and recrystallization (CDRR). The partitioned deformed grains for the higher temperature rolled specimens exhibited a texture similar to the room temperature rolled specimen. The asymmetric rolling introduces a shear component which shifts the texture fibre by ∼5-10 • from the conventional rolling texture. This led to an increase in ductility with little compromise on strength.
Scripta Materialia
We examined the microstructure and texture evolution during the recrystallization annealing of cold rolled Mg-1Y and Mg-0.2Zn-1Y alloys. At the early annealing stage, new grains are nucleated on subunits with 200-300 nm surrounded by dislocation walls within shear bands. The Zn and Y addition reduced the stacking fault energy which results in the high activity of non-basal deformation mechanisms and formation of segregation zones along the stacking faults. This causes the orientation of recrystallization nuclei to be effectively retained so that the texture weakens during the recrystallization without reducing the basal pole split into the sheet transverse direction.
Acta Materialia, 2009
Asymmetric rolling of commercially pure magnesium was carried out at three different temperatures: room temperature, 200°C and 350°C. Systematic analysis of microstructures, grain size distributions, texture and misorientation distributions were performed using electron backscattered diffraction in a field emission gun scanning electron microscope. The results were compared with conventional (symmetric) rolling carried out under the same conditions of temperature and strain rate. Simulations of deformation texture evolution were performed using the viscoplastic self-consistent polycrystal plasticity model. The main trends of texture evolution are faithfully reproduced by the simulations for the tests at room temperature. The deviations that appear for the textures obtained at high temperature can be explained by the occurrence of dynamic recrystallization. Finally, the mechanisms of texture evolution in magnesium during asymmetric and symmetric rolling are explained with the help of ideal orientations, grain velocity fields and divergence maps displayed in orientation space.
Archives of Metallurgy and Materials, 2015
Magnesium alloys are the lightest structural materials, which makes them particularly suitable for use in the aircraft and automotive industry. However, due to hexagonal close-packed crystal structure, resulting in insufficient number of independent slip systems, magnesium alloys exhibit poor formability at room temperature. Conventional methods of work hardening of magnesium alloys requires the temperature about 300°C, which favours simultaneously processes of thermal recovery and grain growth, but decreases beneficial microstructure strengthening effect. Thus, it is a crucial to undertake development of a technology for semi-finished magnesium alloys elements, which will ensure better mechanical properties of the final products by forming desirable microstructure. In the paper we present the development of crystallographic texture of the Mg-based alloy (Mg-AZ31) in the form of pipe extruded at 430°C and subjected to pilger rolling at relatively low temperature.