Xing Jiandong

Phase Structure and Fine Microstructure of In-Situ Vanadium Carbides in Cast High-Vanadium High-Speed Steel

The phase structure and fine-microstructure of in-situ vanadium carbide formed during solidification in cast high-speed steel were studied and observed through high resolution electron microscope (HREM). In addition, the different micro-area compositions in vanadium carbide were analyzed via energy-dispersive spectroscopy (EDS). The results show that vanadium carbides are characterized by large amounts of MC-type nano-particles carbides, an enriched Mo element, distributed in a matrix composed of VC (FCC lattice) and V6C5 (HCP lattice). MC-type nano-particles are coherent or partially coherent with a matrix of vanadium carbide.

Effect of quenching temperature on the microstructure and mechanical properties of Fe-B-Ti alloy

Abstract The effects of quenching temperature on the microstructure and mechanical properties of a cast Fe – B – Ti alloy containing 2.0 wt.% of boron and 1.0 wt.% of titanium were investigated. No clear influence on microstructure has been observed unless the quenching temperature is above 900 °C. As the quenching temperature exceeds 950 °C, most of the boride networks are broken and a large quantity of irregular borides appears. When the quenching temperature reaches 1050 °C, the networks disappear completely. The mechanical properties of the cast Fe – B – Ti alloy begin to improve when the quenching temperature increases. The hardness, impact toughness and bend strength have no obvious change when the quenching temperature exceeds 1000 °C. The cast Fe – B – Ti alloy quenching at 1000 °C has excellent comprehensive mechanical properties, its hardness, bend strength and impact toughness are 58.3 HRC, 2.39 GPa, 17.5 J cm−2 respectively.

Structures and Properties of High-Carbon High Speed Steel by RE-Mg-Ti Compound Modification

The effects of rare earths (RE)-Mg-Ti compound modification on the structures and properties of high-carbon high speed steel (HSS) were researched. The impact toughness (αk), the fracture toughness (K1c) and threshold of fatigue crack growth (ΔKth) are tested. The thermal fatigue test is done on a self-straining thermal fatigue tester, the wear test is done on a high temperature wear test machine. The results show that the matrix can be refined by the RE-Mg-Ti compound modification, the eutectic carbides are inclined to spheroidicize and are distributed evenly, the morphology and distribution of eutectic carbides are unproved by appropriate RE-Mg-Ti complex modification. After RE-Mg-Ti compound modification, a little effects can be found on the strength, hardness and red hardness, but the fracture toughness (K1c) and threshold of fatigue crack growth (ΔKth) are improved in the meantime, the impact toughness (αk) is increased by over one time, and the resistance to thermal fatigue and wear resistance at an elevated temperature are remarkably improved.The effects of rare earths (RE)-Mg-Ti compound modification on the structures and properties of high-carbon high speed steel (HSS) were researched. The impact toughness (αk), the fracture toughness (K1c) and threshold of fatigue crack growth (ΔKth) are tested. The thermal fatigue test is done on a self-straining thermal fatigue tester, the wear test is done on a high temperature wear test machine. The results show that the matrix can be refined by the RE-Mg-Ti compound modification, the eutectic carbides are inclined to spheroidicize and are distributed evenly, the morphology and distribution of eutectic carbides are unproved by appropriate RE-Mg-Ti complex modification. After RE-Mg-Ti compound modification, a little effects can be found on the strength, hardness and red hardness, but the fracture toughness (K1c) and threshold of fatigue crack growth (ΔKth) are improved in the meantime, the impact toughness (αk) is increased by over one time, and the resistance to thermal fatigue and wear resistance at an elevated temperature are remarkably improved.

Effects of Content of MoS2 on Sliding Tribological Behavior of Copper-Based Powder Metallurgy Materials under Electrical Current

Cu-0%,10%,20%MoS2 composite materials were prepared by means of powder metallurgy. By using self-made pin-disk tester, the electribological behavior of pin were investigated against QCr0.5 bronze as disk under electrical sliding. The experimental results indicate that friction coefficient of the Cu- MoS2 powder metallurgy material/bronze pair and wear rates of MoS2 powder metallurgy material are greatly decreased because of MoS2 power added. Under conditions of the electrical current, wear rates are alike between Cu-10%MoS2 and Cu-20%MoS2 composite materials

Use of Artificial Neural Network in Predicting Mechanical Properties of High-Speed Steel (HSS)

This paper is dedicated to the application of artificial neural networks in building prediction models of mechanical properties of new high-speed steel, including predictions of hardness (H) and impact toughness (Ak) according to quenching and tempering temperatures (T1, T2). multilayer backpropagation (BP) networks are created and trained using comprehensive datasets tested by the authors. And very good performances of the neural networks are achieved. The prediction values sufficiently mine the basic domain knowledge of heat treatment process of HSS. A new application field of neural network was developed by the authors

Kinetics of internal oxidation of Cu−Al alloy plate

The kinetics of internal oxidation of dilute Cu−Al alloys, containing up to 2.214% molar fraction Al, was investigated over the temperature range of 1023 K to 1273 K, and the depth of internal oxidation was measured by microscopies. A modified rate equation was derived to describe the kinetics of internal oxidation of Cu−Al alloy plate. Based on the derived equation, the permeability of oxygen in solid copper was obtained from the internal oxidation measurements. The experimental results show that the depth of the internal oxidation is a parabolic function of time, there is no evidence for preferential diffusion along grain boundaries and an outer layer of pure copper was formed on the external surface of samples.