Papers by Keyword: Hot-Compression

Abstract: Hot compression of AZ3l magnesium alloy was carried out at deformation temperatures of 523-723K and strain rates of 0.01-10s^-1. The effects of deformation process on the microstructure and flow stress were investigated. The flow stress curves showed the characteristic of dynamic recrystallization (DRX) with deformation process parameters. Optical microscopy and TEM observations indicated that dynamic recrystallisation and twins structure were found during hot compression. Deformation mechanism of AZ3l magnesium alloy at elevated temperature was discussed in this paper.

Abstract: Hot compression test for AZ3l magnesium alloy at deformation temperatures of 523-723K and strain rates of 0.01-10s-1 were carried out using Gleeble-3500 thermo-mechanical simulator. The experimental results show that the flow stress and microstructure vary apparently with deformation process parameters. Microstructure observations show that dynamic recrystallisation (DRX) takes place during the deformation. The characteristic with the dynamic recrystallization change with the process parameters.

Abstract: The stress-strain behavior of hot-compression Mg-Li alloy was investigated by using a physical simulator Gleeble-3500 system. And the constitutive equation was set up by regression analysis and BP neural networks. Results show that the dynamic recrystallization occured during the hot-compression process. The grain size of the alloy increased and the stress decreased with increasing temperature. Regression analysis indicates that the flow stress can be expressed by hyperbolic sine model and the arithmetic average of errors is 14.13%. Training the flow stress prediction model with MatLab by an improved BP，the maximum arithmetic average of errors is 4.27%. The predicted stress-strain curves are in good agreement with the experimental results.

Abstract: To identify the relationship between grain orientation and precipitation of MnS/AlN particles during hot deformation, cylinder samples containing columnar grains in electrical steels were prepared with different angles between columnar grain axis and sample axis. They were heated at 1360°C and compressed at 1100°C for 50%. Grain orientations and the precipitation states are determined using XRD, EBSD, EDS and SEM. Results indicate a general behavior of less precipitates in <100> and more precipitates in <111> grains. In addition, more precipitates were observed in samples with grain boundaries perpendicular to compression axis.

Abstract: The texture evolution in the surface and center layer of hot rolled electrical steel containing initial columnar grains with their <100> nearly along ND, RD and TD of sheets were determined by EBSD technique. The transition from Goss to Brass or Copper orientation in surface was analyzed. The difference in texture of center layers in these samples was compared. In particular, orientation evolutions within grains and at grain boundaries of different types of orientations were explored. The results are discussed in terms of the special alignments of grain boundaries among columnar grains.

Abstract: The filling capability of forging die is important to design forging die and it exerts a decisive influence to the quality and life of die. Due to the deficiency of the filling capability, and taking Ti₃Al alloy as the research object, at the same height of reducing, work-piece dimensions as the control objective, the finite element numerical simulation method was used to simulate the hot compression of Ti₃Al alloy with DEFORM-3D. This test simulated the process of hot compression, analyzed the hot deforming behavior of the stuff and discussed the effect of work-piece dimension on the variety and distribution of stress and strain.

Abstract: Based on the characteristics of the flow stress curves for one new kind of metastable Ti2448 titanium alloy from isothermal hot compression tests, the constitutive model was developed to describe the relation between flow stress and strain, strain rate, deformation temperature completely. During this process, the flow behavior of alloy at high temperature undergo flow softening caused by dynamic recovery (DRV) was modeled by the adopted hyperbolic sine function based on the unified viscoplasticity theory, the further drop in flow stress after the peak value in stress-strain curves was assumed to be caused by temperature rise and the constitutive model was modified accordingly. Additionally, the material constants were determined by optimization strategies, which is a new method to solve the nonlinear constitutive equation. The stress-strain curves predicted by the developed constitutive model well agree with experimental results, which confirms that the developed constitutive model gives an accurate estimate of the flow stress of Ti2448 titanium alloy and can provide an effect method to model the flow behavior of metastable titanium alloy at high temperature.

Abstract: The effects of hot compression deformation (300°C/0.1s-1) and annealing on the microstructural evolution of ZK60+0.8Zn (ZK60M) alloys were investigated in the present works. Lots of sub-structures were studded in the shear bands under the deformed conditions, and after annealing, the sub-structures in the shear bands occurred static recrystallization following by the growth of recrystallized grains. With the increase of annealing temperature, amounts of twins decrease while static recrystallization (SRX) grains increase while dislocations rearrange forming sub-grains ultimately induced static recrystallization. And that, the micro structural evolution and grain boundary distribution of the specimen as-deformed and as-annealed at different temperatures were analyzed by electron back scatter diffraction (EBSD) data.

Abstract: Among the infrared spectrum, the range of 4-14 μm belonging to far-infrared (FIR) spectrum is named as “growth rays” due to many beneficial effects represented on organisms. Recently, many biomedical materials have been provided and manufactured based on the growth rays for health care as well as complimentary and alternative therapies. In this study, we probed the effect of FIR hot compress on antioxidation ability in human by determining the concentration of superoxide anions in blood. The results revealed that the level of superoxide anions in sympathetic, parasympathetic, and sympathetic plus parasympathetic group was decreased, rather than control group. This suggested that FIR exposure can significantly eliminate superoxide anions and provide protective effect against oxidative damage in human.

Abstract: Hot compression experiments of 304 austenite stainless steel were carried out with Gleeble-1500D simulator under the strain rates of 0.05 s-1~0.5 s-1 at 950°C~1200°C. The effects of temperatures and strain rates on flow stresses during hot compression deformation of 304 austenite stainless steel were investigated. The regression analysis of experiment data was used to evaluated the stress exponent and deformation activation energy, and fit the constitutive equation of the flow stress during hot compression of 304 austenite stainless steel. In addition, the kinetic model and the grain size model of dynamic recrystallization of the steel were obtained by use of the metallographic analysis of the microstructure. The results can provide theoretical basis for design of hot deformation parameters and prediction of microstructure of 304 austenite stainless steel.