High Temperature Deformation Behavior and Dynamic Recrystallization Law of 33Mn2V Steel for Oil Well Tube

Deformation behavior of steel 33Μn2v for oil well tube was studied by hot compression tests conducted at various temperatures and strain rates.The Kumar model was developed to predict the hot deformation behavior of steel 33Mn2V for oil well tube.In this regard,the hot compression tests were carried out at the temperatures from 750°C to 1200°C and at the strain rates of 0.02s1 to 0.16 s1.The experimental data were then used to determine the constants of developed constitutive equations. The Kumar model can be represented by ZenerHollomon parameter in a hyperbolic sinusoidal equation form.The apparent activation energy of deformation is calculated to be 342.1481kJ/Mol.Dynamic recrystallization of steel 33Mn2V occur and the completion of the critical deformation is small,termination error and the initial deformation is smaller.Therefore,its easy for the steel 33Mn2V to the occurrence and completion of dynamic recrystallization.

Study on Hot Deformation Behavior of Ti-6Al-4V-0.1B Alloy with Equiaxed Microstructure

Isothermal compression of Ti-6Al-4V-0.1B alloy was carried out at deformation temperature of 850-980 °C, strain rate of 0.01-1s-1, and maximum height reduction of 60% with Gleeb1500D simulator. The equation between flow stress and strain was gotten for plastic deformation. It shows that the peak flow stress and steady stress were sensitive to the strain rate and temperature except low strain rate and above 950 °C. The activation energy of deformation was obtained in isothermal compression of Ti-6Al-4V-0.1B alloy was 578.29KJ/mol in (α+β) region. The constitutive equation which describes the relationship between the flow stress as a function of strain rate, strain, and deformation temperature were established by adopting the Arrhenius equation:=3.22×1024sinh3.29527(0.0107σ) exp (-578290/ RT).

Hot Deformation Behaviors and Microstructure Evolution in a New PM Nickel-Base Superalloy

The hot deformation behaviors and the effect of flow stress on the microstructure were investigated for the as-HIPed and as-extruded materials in a new PM nickel-base superalloy. Under most test conditions, the as-extruded material exhibits superplastic flow because of grain growth corresponding to work hardening during deformation process, activation energy for deformation of which is 211 kJ/mol. However, activation energy of deformation for the as-HIPed material is 717 kJ/mol, because grain size is refined due to dynamic recrystallization, the reason being considered to be associated with the initial microstructure before the deformation. Based on the results of compression tests, two constitutive equations for the two materials were established using the mathematical regression; these will provide the valuable helps for predicting and controlling the deformed microstructure as well as optimizing hot-working process.

Effects of Rare Earths on the Austenite Recrystallization Behavior in X80 Pipeline Steel

In order to improve the effects of rare earths (RE) as microalloy on the recrystallization behavior in the high strength micro-alloyed steel, the X80 pipeline steels with different RE content were produced with a vacuum induction furnace, a series of hot torsion tests were performed under a range of deformation conditions, and the stress-strain curves were analyzed. The results showed that trace RE would improve the austenite recrystallization behavior. The activation energy of deformation and static recrystallization of the austenite in the X80 pipeline steel without RE additions were respectively 393 and 366 kJ/mol. When the RE addition was 0.0025 wt.%, the activation energy of deformation and static recrystallization were reduced by 33 and 29 kJ/mol respectively. But when the RE addition was increased to 0.0220 wt.%, RE would significantly inhibit the dynamic recrystallization of the austenite, the activation energy of deformation would be increased by 35 kJ/mol, but the activation energy of static recrystallization would reduce by 15 kJ/mol.

Hot Deformation Behavior of SiCw/AZ91 Magnesium Matrix Composite in Compression

The compressive behavior of squeeze cast SiCw/AZ91 composite in the temperature range of 423-723K and in the strain rate range of 0.001-0.25 s-1 was investigated. The compressive true stress-true strain curves were measured and hot deformation microstructures were observed. The strain rate sensitivity exponent (m) of the SiCw/AZ91 composite increased with the increasing of temperature. The activation energy of deformation varied over the range of test conditions examined indicated that the deformation was controlled by more than one mechanism. The reorientation of SiC whiskers in the composite was observed during compression. During the compression, dynamic recovery and dynamic recrystallization occurred in the SiCw/AZ91 composite.

Effect of Silver on Superplastic Deformation in YBa2Cu3O7–x/Ag Composites

Superplastic deformation was studied in fine-grained (0.7–1.1 μm) YBa2Cu3O7–x/Ag composites containing 2.5–25 vol% Ag. The compression tests were conducted in the temperature range of 750–875 °C and at strain rates of 10−5 to 10−3/s. For the YBa2Cu3O7−x/25%Ag composites with grain size of 0.7–1.1 μm, deformed at 800–850 °C and 10−5 to 10−3/s, the stress exponent, grain size exponent, and the activation energy of deformation were 2.0 ± 0.1, 2.5 ± 0.7, and 760 ± 100 kJ/mol, respectively. These values were the same as those of the pure YBa2Cu3O7−x, indicating that the deformation of the composite was controlled by that of the rigid YBa2Cu3O7−x phase. However, the strain rate was increased by the addition of silver as explained by the soft inclusion model of Chen. The dependence of the flow stress on the silver content was in close agreement with the prediction of the model.

Deformation of Ice Single Crystals Close to the Melting Point

Constant strain-rate compression tests on ice single crystals at temperatures between –20°C and -0.2°C are described. The power-law dependence of yield stress on strain-rate gives a value of n which varies from 1.95±0.04 at –0.2°C to 2.07±0.08 at –20°C. The activation energy of deformation varies with strain-rate, but a mean value of 70±2 kJ mol–1 is obtained, with no indication of any increase close to maleting point,as has been found polycrystalline ice. An apparent work-hardening effect, at strains greater than 15%, is explained as being due to bending of the crystal changing the orientation of the basal planes.

Deformation of Ice Single Crystals Close to the Melting Point

Constant strain-rate compression tests on ice single crystals at temperatures between –20°C and -0.2°C are described. The power-law dependence of yield stress on strain-rate gives a value of n which varies from 1.95±0.04 at –0.2°C to 2.07±0.08 at –20°C. The activation energy of deformation varies with strain-rate, but a mean value of 70±2 kJ mol–1 is obtained, with no indication of any increase close to maleting point,as has been found polycrystalline ice. An apparent work-hardening effect, at strains greater than 15%, is explained as being due to bending of the crystal changing the orientation of the basal planes.