The hot tensile deformation behaviors and fracture characteristics of a typical Ni-based superalloy are studied by uniaxial tensile tests under the deformation temperature range of 920-1040 oC and strain rate range of 0.01-0.001 1/s. Effects of deformation parameters on the flow behavior, microstructural evolution and fracture characteristics are discussed in detail. The results show that the flow behaviors are significantly affected by the deformation temperature, strain and strain rate. Under relatively low deformation temperatures (920, 950 and 980 oC), the flow curves are composed of three distinct stages, i.e., work hardening, steady stress and flow softening stages. The flow curves show the typical DRX characteristics under relatively high deformation temperatures (1010 and 1040 oC). With the increase of deformation temperature or the decrease of strain rate, the fraction of recrystallized grains increases. The synthetical effects of localized necking and microvoid coalescence cause the fracture of the studied superalloy under all the deformation conditions. δ phase and carbides are the nucleus for the formation of microvoids. Also, δ phase plays an important role in the coalescence of microvoids.

The hot tensile deformation and fracture behaviors of the hot-rolled AZ31 magnesium alloy were studied by uniaxial tensile tests with the temperature range of 523-723 K and strain rate range of 0.05-0.0005 1/s. Effects of deformation parameters on the strain hardening rate, strain rate sensitivity, microstructural evolution and fracture morphology were discussed. The results show that: (1) The flow curves show a considerable strain hardening stage and no obvious diffuse necking stage under the relatively low temperatures (523 and 573 K). (2) The elongation to fracture increases with the increase of the deformation temperature. But, the sharp drop of the elongation to fracture under 723 K and 0.0005 1/s results from the synthetical effects of the grain growth, inverse eutectic melting reaction (α+β=L) and the incipient melting of α matrix. (3) For the case with the deformation temperature of 623 K and relatively low strain rates, the fracture mechanism is the combination of the void coalescence and intergranular fracture. (4) Under the deformation temperature of 723 K, the fine recrystallized grains experienced a rapid growth and the deformation mechanism is the dislocation creep with the help of inverse eutectic liquid phase. (5) The presence of proper amount of liquid phase on the grain boundary changes the deformation mechanisms, and makes great contribution to the high ductility. However, it will deteriorate the material ductility if the amount of liquid phase is too much.

The effects of the deformation temperature and strain rate on the high-temperature flow behavior of 7075 aluminum alloy were studied by hot compressive tests. Based on the experimental data, the efficiencies of power dissipation and instability parameter were evaluated, and processing maps were constructed by superimposing the instability map over the power dissipation map. Microstructural evolution of 7075 aluminum alloy during the hot compression was analyzed to correlate with the processing maps. Results show that (1) The flow stresses increase with the increase of strain rate and the decrease of deformation temperature; (2) The high-angle boundaries and coarse precipitations distributing in the grain interior/boundaries, which may result in the deep inter-granular corrosion and large areas of denudation layer, should be avoided in the microstructures of the final products; (3) The optimum hot working domain is the temperature range of 623-723 K and strain rate range of 0.001-0.05 s-1.

Creep-aging forming, combining both the aging treatment and forming process, has recently drawn much attention of researchers. In this study, the effects of creep-aging processing on the corrosion resistance and mechanical properties of a typical Al-Cu-Mg alloy are investigated by electrochemical corrosion, exfoliation corrosion and uniaxial tensile experiments. The results show that the corrosion resistance and mechanical properties of the studied Al-Cu-Mg alloy are strongly sensitive to the creep-aging processing parameters. The creep-aging processing can change the dimension and density of nanoprecipitates, which greatly affects the corrosion resistance and mechanical properties of the studied Al-Cu-Mg alloy. With the increase of creep-aging temperature, the corrosion resistance and the elongation decrease, while the yield strength and ultimate tensile strength increase. For the materials creep-aged in “under aging” and “peak aging” conditions, the applied stress can increase the ultimate tensile strength, but deteriorate the corrosion resistance.

The creep-aging behaviors of 7075 aluminum alloy are studied by uniaxial tensile creep experiments under elevated temperatures. The effects of creep-aging temperature and applied stress on the precipitates of 7075-T651 aluminum alloy are investigated using scanning electron microscope (SEM) and transmission electron microscope (TEM). Results show that: (1) Coarse insoluble precipitates ( and ) and intermediate precipitates ( and ) are found in the aluminum matrix, and the effects of creep-aging treatment on these precipitates are not obvious; (2) The main aging precipitates are and phases, and the aging precipitates grow up with the increase of creep-aging temperature and applied stress; (3) With the increase of creep-aging temperature and applied stress, the precipitates are discontinuously distributed on the grain boundary, and the width of precipitate free zone increases with the increase of creep-aging temperature and applied stress; (4) Compared with the microstructure in the traditional stress-free aged sample, the creep-aging process can refine the precipitates and narrow the width of the precipitate free zone.