Papers by Author: Li Bin Niu

Abstract: The microstructure and corrosion behavior of commercial AZ91/AZ91-0.4%Nd alloys were investigated by OM, immersion test and weight-loss method. It was found that the number of Nd element in the AZ91 magnesium alloy has effect on the grain refining efficiency, the coarse β-Mg₁₇Al₁₂ phase distributed along the grain boundaries transformed into granular, and the granular or acicular Al₃Nd phase precipitated in matrix. The addition of Nd element significantly reduces the corrosion rate of AZ91-0.4%Nd magnesium alloy, as a result the corrosion resistance of alloy was improved obviously.

Abstract: In the paper, titanium tri-aluminide (Al₃Ti) particles reinforced aluminium (Al)-based composite coatings were fabricated by infiltration plus in-situ techniques at 891.3 °C. The obtained composite coatings are characterized by XRD, SEM and friction and wear testers. The experimental results show that the reaction between Ti wires and Al molten increases with extending time, Ti wires can totally transform into Al3Ti particles for 20 min, which present blocky and strip-like states, respectively. The wear rates of the composite coatings decrease with increasing time.

Abstract: The atomic diffusion and mechanical properties of as-cast AZ80 magnesium alloy after solution treatment at different time were studied by OM,SEM,EDS as well as tensile testing. The results show that the coarse β-Mg₁₇Al₁₂ phase distributed along the grain boundaries as net microstructure is almost dissolved after solution treatment, and the content of Al that in the α-Mg matrix is well distributed with the solution time prolonged. Because of the β-Mg₁₇Al₁₂ phase reducing and granulating, the function of precipitates phase strengthening was depressed and the hardness (HB) of alloy dropped obviously. However, the tensile strength(σb ) and elongation(δ) enhanced remarkably and the yield strength (σ_0.2) decreased slightly.

Abstract: The microstructure and element distribution of AZ80 magnesium alloy as-cast and after annealing treatment were studied by OM, SEM, XRD, EDS and TEM. The results show that the coarse divorced eutectic phase distributed along the grain boundary dissolve into Mg matrix during the isothermal process at 415°C for 24h. During the cooling process of annealing treatment, the lameller-shape β-Mg₁₇Al₁₂ nucleated preferentially in the grain near the boundary, then grows towards the neighbor grains with longitudinal direction, which precipitated from magnesium solid solution as perlite-type precipitation. When cooled to room temperature, the lameller-shape β-Mg₁₇Al₁₂ was uniformly distributed in the matrix, and the lamellar spacing inside β phase is about 1-2μm.

Abstract: In the paper, tungsten carbide (WC) particles can be in-situ synthesized by applying electromagnetic field to the system consisting of tungsten wires and gray cast iron melt at 1573 K. The microstructures and wear-resistant properties of composites reinforced by both WC particles and the residual tungsten wires were investigated by XRD, SEM, EDS, micro-hardness and pin-on-disc wear measurements. The results show that, with enhancing frequencies of electromagnetic field from 0 to 5 KHz, the amounts of in-situ WC particles increased and of the residual tungsten wires gradually decreased until tungsten wires completely reacted. Due to the higher hardness of in-situ WCp(2100-2231HV0.1) and the strong interfacial bonding, the composites displayed an excellent wear-resistant properties. When the frequency was 5 kHz, the wear loss for the composite fabricated was optimal and 2.69 times lower than that of reference samples.