Guangjie Huang

Influence of rolling ways on microstructure and anisotropy of AZ31 alloy sheet

Abstract Two rolling ways, unidirectional rolling and cross rolling, were carried out on twin roll cast AZ31 alloy sheet to study the influence of strain path change on the evolution of the rolling microstructure and texture as well as the anisotropic properties of AZ31 alloy sheet with microscopy, X-ray diffraction technique and tensile tests. It is found that cross rolling gives rise to more uniform microstructure and stronger texture intensities compared with unidirectional rolling. The differences in the microstructure and texture intensities are reflected in the anisotropy characterized by the difference in the yield stress and the fracture elongation that were measured along directions in the rolling plane at angles of 0°, 45° and 90° from the rolling direction.

Effects of strain rate and temperature on microstructure and texture for AZ31 during uniaxial compression

Abstract In order to investigate the effects of strain rate and temperature on the microstructure and texture evolution during warm deformation of wrought Mg alloy, AZ31 extruded rods were cut into cylinder samples with the dimension of d 8 mm×12 mm. The samples were compressed using a Gleeble 1500D thermo-mechanical simulation machine at various strain rates (0.001, 0.01, 0.1, 1 and 5 s −1 ) and various temperatures (300, 350, 400 and 450 °C). The microstructure and texture of the compressed samples at the same strain under different deformation conditions were studied and compared by electron backscatter diffraction (EBSD) in scanning electron microscope (SEM). The results show that the size of recrystallized grains in the deformed samples generally increases with the decrease of strain rate and the increase of temperature. After 50% reduction, most basal planes are aligned perpendicular to the compression direction at relatively high strain rate (>0.01 s −1 ) or low temperature ( −1 for uniaxial compression at 300 °C, which produces about 80% of small grains (

Effect of extrusion processing parameters on microstructure and mechanical properties of as-extruded AZ31 sheets

Abstract The AZ31 sheets were prepared by extrusion. The effects of the extrusion processing parameters including the temperature, extrusion ratio, and structure of the extrusion die on the microstructure and mechanical properties of the as-extruded AZ31 sheets were investigated. The results show that the partial grains grow abnormally and the mechanical and anisotropic properties of the as-extruded AZ31 sheets have little change at the extrusion temperatures of 380–400 °C and the extrusion ratio of 13.3. With the increase of the extrusion ratio, the microstructure of the as-extruded AZ31 sheets by conventional die becomes finer and more uniform, and the elongation rate increases, but the strength decreases and its anisotropy becomes worse. Under the porthole die, finer and more uniform microstructure, higher mechanical properties and better anisotropy can be brought for the as-extruded AZ31 sheets. The extruded AZ31 sheets by the porthole die have better anneal process of 300°C and 1 h.

Microstructure and texture evolution of AZ31 magnesium alloy during rolling

Abstract The production of magnesium alloy sheets normally involves several processing stages including hot rolling, cold rolling and intermediate annealing. The microstructure and texture evolution of AZ31 magnesium alloy sheets in different processing states were investigated by optical microscopy and X-ray diffraction technique. It is found that the microstructure of hot-rolled sheets is dominated by recrystallized equiaxed grains, while that of cold-rolled sheets is dominated by deformation twins. With final annealing applied on the cold-rolled sheets, fine recrystallization grains are obtained and ductility of the samples is increased. It is also found that the texture of magnesium alloy sheets prefers the basal texture, and other compositions of texture are relatively weak. Moreover, final annealing does not significantly affect texture distribution. The results of this study provide useful guidelines for optimizing the processing of magnesium alloys.

Flow behavior and microstructure evolution of 6A82 aluminium alloy with high copper content during hot compression deformation at elevated temperatures

The flow behavior and microstructure evolution of 6A82 aluminum alloy (Al–Mg–Si–Cu) with high copper content were studied on a Gleeble–1500 system by isothermal hot compression test in the temperature range from 320 to 530 °C and the strain rate range from 0.001 to 10 s−1. The results reveal that the flow stress of the alloy exhibits a continuous flow softening behavior at low temperatures of 320–390 °C, whereas it reaches steady state at high temperatures (≥460 °C), which are influenced greatly by the Zener–Hollomon parameter (Z) in the hyperbolic sine with the hot deformation activation energy of 325.12 kJ/mol. Microstructure characterizations show that prominent dynamic recrystallization and coarsening of dynamic precipitation may be responsible for the continuous flow softening behavior. Due to deformation heating at high strain rates (≥1 s−1), dynamic recrystallization is more prominent in the specimen deformed at 530 °C and 10 s−1 than in the specimen deformed at 460 °C and 0.1 s−1 even though they have very close ln Z values.

Microstructure characterization of Al-cladded Al–Zn–Mg–Cu sheet in different hot deformation conditions

Abstract Al-cladded Al–Zn–Mg–Cu sheets were compressed up to 70% reduction on a Gleeble–3500 thermo-mechanical simulator with temperatures ranging from 380 to 450 °C at strain rates between 0.1 and 30 s−1. The microstructures of the Al cladding and the Al–Zn–Mg–Cu matrix were characterized by electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD). The microstructure is closely related to the level of recovery and recrystallization, which can be influenced by deformation temperature, deformation pass and deformation rate. The level of recovery and recrystallization are different in the Al cladding and the Al–Zn–Mg–Cu matrix. Higher deformation temperature results in higher degree of recrystallization and coarser grain size. Static recrystallization and recovery can happen during the interval of deformation passes. Higher strain rate leads to finer sub-grains at strain rate below 10 s−1; however, dynamic recovery and recrystallization are limited at strain rate of 30 s−1 due to shorter duration at elevated temperatures.

Hot-deformation behaviors of AZ31 alloys with different initial states

Abstract The hot-deformation behaviors of three types of AZ31 samples, extruded sheet, hot rolled sheet and cast rod were studied. These samples had different initial grain size and texture. Compression deformation of these samples was carried out using a Gleeble 1500D under a series of thermal deformation conditions. Microstructure and texture of the initial and deformed samples were examined using electron backscatter diffraction (EBSD) techniques. The flow curves for all these three types of samples shifted upward with strain rate increasing. Significant grain refinement was noticed in the hot rolled sheet sample. The grain size was reduced to 3.7 μm after 50% (ɛ=0.69) compression. The DRX grains in both the extruded rod and hot rolled sheet samples presented the same basal plane texture, irrespective of the difference in the initial texture of the samples.

Comparison of microstructure and properties of AZ31 Mg alloy sheet produced through different routes

Abstract Slabs fabricated by means of three different ingot breakdown modes: hot-rolling, extrusion-rolling and twin-roll strip continuous casting-cum-rolling, were rolled into sheets and then annealed. Both the rolled and annealed sheets were investigated by SEM-EBSP, BSE, X-ray diffraction and tensile test, and compared in terms of microstructure, texture, and mechanical properties. Effects of different processing methods on the microstructure, texture and the related mechanical properties were discussed based on the experimental results.

Improvement of strength and ductility of Al-Cu-Li alloy through cryogenic rolling followed by aging

Abstract To develop an improved approach in achieving an excellent combination of high strength and ductility, the solutionized Al-Cu-Li plates were subjected to rolling at cryogenic and room temperatures, respectively, to a reduction of 83%, followed by aging treatment at 160 °C. The results indicate that Al-Cu-Li alloys through cryogenic rolling followed by aging treatment possess better mechanical properties. Rolling at cryogenic temperature produces a high density of dislocations because of the suppression of dynamic recovery, which in turn promotes the precipitation of T 1 (Al 2 CuLi) precipitates during aging. Such high density of T 1 precipitates enable effective dislocation pinning, leading to an increase in strength and ductility. In contrast, room temperature rolled alloys after aging treatment exhibit lower strength and ductility due to low density of T 1 precipitates in the grain interior and high density of T 1 precipitates around subgrain boundaries.