Hot compressive deformation behaviors and micro-mechanisms of TA15 alloy

The hot deformation behaviors of TA15 alloy,as well as the microstructure obtained after compressive deformation,were investigated.The results show that TA15 alloy exhibits a peak stress when deformed at temperature lower than 900 ℃,implying recrystallization characteristics.However,steady flow stress-stain behavior is observed without peak stress when deformation is employed at temperature higher than 900 ℃,showing recovery characteristics.Micro-deformation band appears at deformation temperature of 750 ℃,and equiaxed grains are found at 800 ℃,implying the occurrence of recrystallization.When deformed at 925 ℃,the specimen shows the recovery characteristics with dislocation networks and sub-grain boundaries.

Effects of hot compression deformation temperature on the microstructure and properties of Al–Zr–La alloys

The main goal of this study is to investigate the microstructure and electrical properties of Al–Zr–La alloys under different hot compression deformation temperatures. In particular, a Gleeble 3500 thermal simulator was used to carry out multi-pass hot compression tests. For five-pass hot compression deformation, the last-pass deformation temperatures were 240, 260, 300, 340, 380, and 420°C, respectively, where the first-pass deformation temperature was 460°C. The experimental results indicated that increasing the hot compression deformation temperature with each pass resulted in improved electrical conductivity of the alloy. Consequently, the flow stress was reduced after deformation of the samples subjected to the same number of passes. In addition, the dislocation density gradually decreased and the grain size increased after hot compression deformation. Furthermore, the dynamic recrystallization behavior was effectively suppressed during the hot compression process because spherical Al;Zr precipitates pinned the dislocation movement effectively and prevented grain boundary sliding.

The Dislocation Sub-structure Evolution during Hot Compressive Deformation of Ti-6Al-2Zr-1Mo-1V Alloy at 800℃

Hot compressive behaviors of Ti-6Al-2Zr-1Mo-1V alloy at 800℃, as well as the evolution of microstructure during deformation process, were investigated. The experimental results show that flow stress increases to a peak stress followed by a decease with increasing strain, and finally forms a stable stage. Dislocations are generated at the interface of αβ phase, and the phase interface and dislocation loops play an important role in impeding the movement of dislocation. As strain increasing, micro-deformation bands with high-density dislocation are formed, and dynamic recrystallizaton occurs finally. XRD Fourier analysis reveals that dislocation density increases followed by a decrease during compressive deformation, and falls into the range from 10^10 to 10^11 cm^-2.

Gaussian process regressions on hot deformation behaviors of FGH98 nickel-based powder superalloy

The hot deformation behaviors of FGH98 nickel-based powder superalloy were experimentally investigated and theoretically analyzed by Arrhenius models and machine learning(ML).Hot compression tests were conducted with a Gleeble-3800 thermo-mechanical simulation machine on the FGH98 superalloy at strain rates of 0.001–1 s–1 and temperatures of 1025–1175℃.The peak stresses under different deformation conditions were analyzed via the Sellars model and an ML-inspired Gaussian process regression(GPR)model.The prediction of the GPR model outperformed that from the Sellars model.In addition,the stress-strain responses were predicted by the GPR model and tested by experimentally measured stress-strain curves.The results indicate that the developed GPR model has great power with wide generalization capability in the prediction of hot deformation behaviors of FGH98 superalloy,as evidenced by the R2 value higher than 0.99 on the test dataset.

Novel cobalt base superalloy and its high-temperature flow behavior

A novel cobalt base superalloy containing titanium and aluminum was investigated through metallography, tensile test, and high-temperature isothermal compression deformation. The results show that proper content of titanium and aluminum with can improve the strength and ductility of the cobalt base superalloy. The Co3（Ti,Al） compound with L12 structure precipitates when the novel superalloy is aged at 800℃ for 20 h. The e phase with hcp structure also precipitates when the superalloy is deformed by 28% and then aged at 650℃ for 4 h. The e phase can exist at 800℃. The superalloy has excellent high-temperature mechanical properties. Its maximum flow stress at 850℃ is in the range of 360-475 MPa when the strain rate is between 0.0021 and 2.1 s^-1. The flow stress of the superalloy during high-temperature deformation can be described by the Zener-Hollomon parameter with a hot deformation activation energy of 397 kJ.mol^-1.

High temperature deformation behavior and processing map of hot isostatically pressed Ti-47.5Al-2Cr-2Nb-0.2W-0.2B alloy using gas atomization powders

The hot compressive deformation behavior of hot isostatically pressed Ti-47.5Al-2Cr-2Nb-0.2W-0.2B alloy using gas atomization powders was systematically investigated and the processing map was obtained in the temperature range of 1323-1473 Kand strain rate range of 0.001-0.5s^（-1）.The calculated activation energy in the above variational ranges of temperature and strain rate possesses a low activation energy value of approximately 365.6kJ/mol based on the constitutive relationship models developed with the Arrhenius-type constitutive model respectively considering the strain rate and deformation temperature.The hot working flow behavior during the deformation process was analyzed combined with the microstructural evolution.Meanwhile,the processing maps during the deformation process were established based on the dynamic material model and Prasad instability criterion under different deformation conditions.Finally,the optimal hot processing window of this alloy corresponding to the wide temperature range of 1353-1453 Kand the low strain rate of 0.001-0.1s^（-1） was obtained.

Effect of squeeze casting process on microstructures and flow stress behavior of Al-17.5Si-4Cu-0.5Mg alloy

The effects of squeeze casting process on microstructure and flow stress behavior of Al-17.5Si-4Cu-0.5Mg alloy were investigated and the hot-compression tests of gravity casting and squeeze casting alloy were carried out at 350-500°C and 0.001-5s-1.The results show that microstructures of Al-17.5Si-4Cu-0.5Mg alloys were obviously improved by squeeze casting.Due to the decrease of coarse primary Si particles,softα-Al dendrite as well as the fine microstructures appeared,and the mechanical properties of squeeze casting alloys were improved.However,when the strain rate rises or the deformation temperature decreases,the flow stress increases and it was proved that the alloy is a positive strain rate sensitive material.It was deduced that compared with the gravity casting alloy,squeeze casting alloy（solidified at 632 MPa）is more difficult to deform since the flow stress of squeeze casting alloy is higher than that of gravity casting alloy when the deformation temperature exceeds 400°C.Flow stress behavior of Al-17.5Si-4Cu-0.5Mg alloy can be described by a hyperbolic sine form with Zener-Hollomon parameter,and the average hot deformation activation energy Q of gravity casting alloy and squeeze casting alloy is 278.97 and 308.77kJ/mol,respectively.