Daoguang He

The presence of complex microstructures, including deformed grains and high‐density substructures formed during spinning, profoundly impacts the mechanical properties of spinning Hastelloy C‐276 components. This work aims to investigate the microstructural evolution and mechanical property changes of spun Hastelloy C‐276 superalloy components during annealing. Experimental results confirm that subgrain aggregation/coalescence and reconfiguration of dislocation networks/cells through cross‐slip/annihilation occur with a rise in annealing temperature or prolonged time, which also promotes the nucleation/coarsening of static recrystallization (SR) grains. The precipitation of tiny granular μ‐phases is accelerated at higher annealing temperatures or longer durations, but the microstructure undergoes a notable transition for temperatures arriving at 1050°C, where the tiny μ‐phases diminish and give way to coarsened, short‐rod morphologies. In addition, the microstructure consisting of uniformly distributed fine SR grains and dispersed μ‐phases obtained under elevated annealing temperatures or prolonged holding times leads to a simultaneous enhancement in mechanical strength. Meanwhile, it promotes dimple coalescence and the formation of serpentine slip bands and toughness dimples.

This study investigates the effects of different porosities (0%, 11%, 19.6%, 28.3%) on the discharge behavior and corrosion resistance of 1060 Al alloy anodes in a 4 M NaOH electrolyte. Results indicate that the medium-porosity sample (MP, 19.6%) exhibits optimal comprehensive performance: a high polarization resistance of 22253 Ω·cm2, a corrosion current density of 2.793×10-3 mA·cm-2, the most stable discharge plateau and minimal voltage decay across a broad current density range of 2–40 mA·cm-2, along with uniform corrosion morphology. This study demonstrates that a 19.6% porosity achieves an optimal balance between effective expansion of the reaction interface and uniformity of current distribution, providing experimental evidence for the structural design of low-cost Al-air battery anodes.

The AA7075 holds significant importance in the aerospace field. Understanding its microstructure evolution and constitutive relationships during warm deformation is crucial for optimizing forming processes. To this end, isothermal compression experiments were conducted at different temperatures and strain rates to analyze their flow stress behavior. The microstructure evolution was characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Microstructural analysis confirmed that dynamic recovery constitutes the predominant softening mechanism under warm forming conditions. The results indicate that flow stress is highly sensitive to deformation parameters, decreasing with increasing temperature and rising with increasing strain rate. To accurately describe the flow behavior, two distinct constitutive models were formulated: (1) a phenomenological Hensel–Spittel–Garofalo (HSG) model; (2) a novel hybrid machine-learning model that innovatively integrates the Harris Hawks Optimization (HHO) algorithm with an LSTM model. Both constitutive models demonstrate reasonable predictive accuracy. In comparison, the HHO-LSTM model demonstrated a superior ability to capture complex nonlinear relationships, achieving highly precise predictions of flow stress across the full range of deformation conditions tested in this work. The hybrid machine-learning model proposed in this study provides a highly accurate method for describing and predicting the flow behavior of the AA7075 during warm forming, offering a powerful predictive tool for engineering applications.

The deformation mechanism and static recrystallization (SRX) behavior of an Ni-based single-crystal superalloy are investigated. Indentation tests were performed to investigate the effects of crystal orientation and external stress on SRX behavior. Following solution heat treatment, the depth of the SRX layer below the indentation increases with a deviation angle (β) from the [001] orientation. The slip analysis indicates that an increased deviation angle leads to an increase in the resolved shear stress on the slip plane and a decrease in the number of active slip systems. In addition, the variation pattern of the SRX layer depth with the deviation angle is consistent for different external stresses. The depth of the SRX layer also increases with external stress. The coarse γ′ phases and residual γ/γ′ eutectics obviously enhance the pinning effects on the expansion of recrystallized grain boundaries, resulting in slower growth rates of the recrystallized grains in interdendritic regions than those in dendrite core regions.

High-temperature tensile tests were developed to explore the flow features of an Al-Zn-Mg-Cu alloy. The fracture characteristics and microstructural evolution mechanisms were thoroughly revealed. The results demonstrated that both intergranular fractures and ductile fractures occurred, which affected the hot tensile fracture mechanism. During high-temperature tensile, the second phase (Al₂CuMg) at the grain boundaries (GBs) promoted the formation and accumulation of dimples. With the continual progression of high-temperature tensile, the aggregation/coarsening of dimples along GBs appear, aggravating the intergranular fracture. The coalescence and coarsen of dimples are reinforced at higher tensile temperatures or lower strain rates. Considering the impact of microstructural evolution and dimple formation/coarsening on tensile stresses, a physical mechanism constitutive (PMC) equation is herein proposed. According to the validation and analysis, the predictive results were in preferable accordance with the testing data, showing the outstanding reconfiguration capability of the PMC model for high-temperature tensile features in Al–Zn–Mg–Cu alloys.

High-temperature forming behaviors of a 7046-aluminum alloy were investigated by hot compression experiments. The microstructural evolution features with the changes in deformation parameters were dissected. Results indicated the formation of massive dislocation clusters/cells and subgrains through the intense DRV mechanism at low compression temperature. With an increase in deformation temperature, the annihilation of dislocations and the coarsening of subgrains/DRX grains became prominent, due to the collaborative effects of the DRV and DRX mechanisms. However, the growth of subgrains and DRX grains displayed the weakening trend at high strain rates. Moreover, two constitutive models involving a physically based (PB) model and a gate recurrent unit (GRU) model were proposed for predicting the hot compression features. By validation analysis, the predicted values of true stress perfectly fit with the experimental data, indicating that both the proposed PB model and the GRU model can accurately predict the hot compression behaviors of 7046-aluminum alloys.