Papers by Author: Tian Fu Jing

Abstract: The warm deformation behavior of as-quenched and as-annealed ASTM 1045 steel was studied by isothermal compression testing on a Gleeble3500 machine. The temperature range was 550-700°C and the strain rate range 0.001-0.1s^-1. Transmission electron microscopy (TEM) was used to study the microstructures associated with the observed deformation phenomenons. The results show that the flow stress of quenched specimens is higher than that of annealed ones at 550°C when strain rates are greater than 0.001s^-1. However, at 600-700°C and strain rate of 0.001s^-1, the whole flow curves of quenched specimens are below that of annealed ones. Under the rest conditions, the flow stress of quenched specimens is higher at the beginning of compression and then the opposite is true after the strain is greater than a critical value. The microstructure examination proves that the dynamic recrystallization easily occurs in quenched specimens during warm compression, which results in the above phenomenons. Keywords: warm deformation, flow stress, steel, quenching, annealing

Abstract: Specimens of medium carbon steel were quenched and warm-compressed on a Gleeble 3500 Machine. The microstructure of the specimens was studied by using an optical microscope and a transmission electron microscopy. And the properties were investigated by using tensile tests and hardness tests. Results show that the starting microstructure is lath martensite with a small amount of flake martensite. After 50% compression at 550-650°C, ultrafine grains can be observed in the specimens. The microstructure of the specimens compressed at 600°C is equiaxed ultrafine ferrite grains + nano-carbides and a good combination of strength and ductility is obtained. The tensile strength and total elongation are 861MPa and 19.1%, respectively. The hardness is 233.81Hv.

Abstract: The bulk nano-crystalline cobalt-nickel alloys have been prepared by the double refined methods (DRM) combined the high-speed jet electrodeposition (JED) with the additive added in jet electrolyte, and their microstructure and properties, such as the microhardness and magnetic properties, have been evaluated. The results indicate that the DRM is a very effective technique for grain size refinement and property improvement. The concentration of the additive added in the jet electrolyte has little effect on the Co-content in the deposited alloys, but they have a remarkable effect upon the microstructure and properties.