Search

Al-Ti-C master alloys were fabricated by using aluminum melt reaction method with graphite powders (GPs) or carbon nanotubes (CNTs) as carbon source. The microstructure formation during the reaction process was analyzed. The α-Al grain refinement abilities of the master alloys were checked. The results demonstrate that the TiC particles form mainly through the reaction between the solid C (GPs or CNTs) and the solute Ti. Using CNTs as the carbon source can significantly enhance the recovery rate of carbon and promote the formation of Al-Ti-C master alloy with a well dispersed microstructure and high α-Al grain refining ability. [ABSTRACT FROM AUTHOR]

Recently, an efficient integrated forging process has been proposed in which solutionized aluminum alloy extruded bars are directly hot forged and quenched. In this study, the hot deformation behaviors and microstructure evolution of 6082 aluminum alloy extruded bar was investigated via isothermal compression tests under the temperature range of 400–535 ℃ and strain rates range of 0.1–10 s−1 with different strains. The deformation behaviors were described by the established strain-compensated constitutive model and processing maps. The microstructure evolution of the deformed specimens was revealed by electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). It was found that the Zener-Hollomon (Z) parameter, which involved temperature and strain rate, exerted a considerable influence on the deformation behaviors and microstructure evolution. Deformation-induced extensive dislocations were pinned by the dispersoids and generated cellular substructures under high ln Z (i.e. low temperature or high strain rate), potentially triggering dynamic instability. The tangled dislocations pinned by the insoluble dispersoids continued to overcome the pinning points as ln Z decreased, while the dislocations were consumed by the rotation of subgrain boundaries. As a result, the geometrically necessary dislocation (GND) was decreased with the significant increase of the fraction of high angle grain boundaries (HAGBs). In addition, the stable-end orientations, namely, Brass {011}< 211 > and Goss {011}< 001 > texture components with high Schmid Factors (SFs) are generated during compression, facilitating the dislocation movement and thus promoting the fraction of recrystallization. The above findings demonstrate the foundation for improving forming performance and optimizing the processing parameters for the integrated forging process. • The flow behaviors of solutionzied 6082 aluminum alloy extruded bars were investigated. • The relationship of the dominant softening mechanisms and the Z parameter was revealed. • Evolution of grain boundaries misorientation and geometrically necessary dislocation was illustrated. • The characteristics of grain orientation and Schmid Factors were investigated. [ABSTRACT FROM AUTHOR]

As an emerging technology to solve the bottleneck of plastic processing of light alloys, electromagnetic forming usually causes a complex mechanical response and microstructure evolution of materials. In this work, based on the electromagnetic ring expansion (EMRE) experiment, the relationship between microstructure evolution and mechanical properties of AA2219-T6 under EMRE with different discharge energies is established. In particular, to reveal the influence of strain and temperature parameters on the output response during the electromagnetic pulse process, a Q235 steel sleeve and an epoxy resin sleeve with different thermal conductivities are applied to constrain the deformation of the ring, respectively, thus the performance under electromagnetic treatment (EMT) are investigated. It is found that, under the threshold discharge energy of 4.23 kJ, the microhardness of the ring via EMT with the steel sleeve is similar to that of AA2219-T6, but increases by 20.9% compared with the ring via EMT with the epoxy sleeve and 17.1% compared with the ring via EMRE. The electromagnetic pulse has no significant effect on the evolution of precipitates in AA2219-T6-EMT (Steel), but the adiabatic temperature rise in AA2219-T6-EMT (Epoxy) caused redissolution of G.P.Ⅱ zones. With the gradual increase of discharge energy under EMRE, the microhardness of AA2219-T6 increases initially and followed by a decrease, while the fracture strain increases continuously. When discharge energy reaches 8.63 kJ, 2219 aluminum alloy has the optimal mechanical properties that, compared with AA2219-T6, the microhardness increased by 14.2% and the fracture strain increased by 18.0%. The dislocation density shows a trend of first increasing and then decreasing with the increase of discharge energy. Combined with the observed phase transformation, it is shown that dislocations generated by EMRE will promote G.P.Ⅱ zones to transform into θ ′′ phases, and affected by dislocation density, the transformation effect is most obvious at 8.63 kJ. In addition, the transformation of precipitates greatly increases the probability of hindering the motion of dislocations, which promotes the precipitates to be dispersed, and AA2219-T6 is further strengthened after EMRE. As discharge energy continues to increase, the dislocations begin to annihilate and G.P.Ⅱ zones are redissolved due to the adiabatic temperature rise. • G.P.Ⅱ zones are redissolved with a significant temperature rise in EMRE and EMT. • EMRE promotes the instant phase transformation affected by dislocation density. • The optimal performance under EMRE is obtained at a discharge energy of 8.63 kJ. [ABSTRACT FROM AUTHOR]