The Deformation Behaviors and Mechanism of the High-Temperature Mechanical Properties of a Ni48W35Co17 Alloy

Investigations of the plastic deformation mechanisms of Ni-W-based heavy alloys varying with increasing temperatures are very important for the development of hot forming processes and applications at elevated temperatures. In this study, the continuous variation of strength and plasticity of a novel Ni-W-based heavy alloy with increasing temperatures was investigated. The tensile strength of a Ni48W35Co17 sample at 600 °C was 471 MPa, which was 47% lower than that at 100 °C. A variation in an abnormal decrease in elongations at temperatures from 400 °C to 800 °C was found in this alloy. The elongation rate of the sample tensile at 600 °C was 19%, which was 73% lower than that at 100 °C. A microstructural analysis revealed that the number of twins in the sample tensile at a temperature higher than 600 °C increased considerably compared with the sample tensile at lower temperatures, indicating that the dislocation slips were suppressed during the high-temperature stretching process. The precipitates of the NiW phase were found in the 600 °C tensile sample, which was not clearly observed in the 400 °C tensile sample, suggesting that dislocation slips were affected by the formation of these precipitates. Moreover, the orientation relationship between the matrix and NiW phase was (200)Ni//(240)NiW and [001]Ni//[001]NiW. The tiny precipitated phase was the main reason for the plasticity decrease of the alloy with the temperature increase.

Application of Finite Element Analysis Software MSC.Marc in Material Tests

The process of using finite element analysis software MSC.Marc to simulate Q345 smooth cylinder tensile sample damage. The result shows that the breaking and crack growth process of materials may be well simulated by using Gurson model and improved damage parameters. The nucleation of internal holes in the material, growth, polymerization and the damage of the material is a very quick process. The material damage process may be accurately simulated by taking the strain of the necking of the tensile sample as the nucleation strain of the holes in the material.

Fracture Behaviors of the Rolled Isotactic Polypropylene

The mechanical properties of the rolled isotactic polypropylene and the morphology of fracture surfaces were measured and observed by tensile tests and the scanning electron microscopy. And then the tensile fracture behaviors along the rolling and transvers directions of the rolled samples were analyzed. After rolling, strong anisotropy mechanical properties occurred along the rolling and transverse directions: high tensile strength with low total elongation along the rolling direction and low tensile strength with high total elongation along the transverse direction. After tensile test, three characteristic structures were found on the fracture surfaces. The tensile fracture behavior of the rolled samples is: stress concentration happens on the edge of tensile sample and then fracture develops to the center part of the tensile sample. When the fracture is big enough, the tensile sample will be failed very quickly.

Hot Ductility Behaviors of HRB600 Vanadium-Containing Steel Rebar

Hot ductility behaviors of HRB600 vanadium-containing steel rebar was study with thermal simulation test and the fracture was observed and analyzed by scanning electron microscope (SEM). The result shows that, the contraction ratio of cross sectional area (Z) in 1050°C - 1300°C was more than 60%, tensile sample showed good ductility; Z in 750°C-1000°C was less than 60%, tensile sample showed brittle, namely third brittle zone. Then third brittle zone should be avoided or minimize stays in the development process of continuous casting and hot rolling. The fracture mode and the morphology of fracture surfaces were different at different temperatures.

Study on the Relationship between Tensile Sample Lamination and Inner Quality of Q345 Slabs

In order to find the relationship between tensile sample laminations and inner quality of Q345 slabs, casting trials in conditions of with and without EMS and different superheating have been carried out. It is found that slab inner quality can be improved a lot with EMS, center equiaxial grain ratio increases greatly. Lowering superheating leads to downgrading of center deviation, however, center equiaxial grain ratio increases not too much compared with EMS. Tensile samples produced by above-mentioned measures do not break in the center area.