Papers by Author: Jian Hua Liu

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Authors: Yu Wen Liu, Lin Liu, Wei Zhang, Jian Hua Liu, Gui Rong Peng, Rui Jun Zhang
Abstract: Effects of high pressure heat treatment on the microstructure refinement and corrosion resistance of brass were studied by means of metallographic observation, SEM/EDX, profilometer and CH1660A electrochemical instrument. Brass were heated from 23°C to 700°C and kept at 700°C for 10 minutes under high pressure of 1GPa, 3GPa, 4GPa and 6GPa, respectively. The results show that high pressure heat treatment has great influence not only on the microstructure refinement of the alloy but also on its corrosion resistance in HCl solution. Under 3GPa, the refined microstructure can be found and the corrosion resistance of the alloy changes into much worse. However, under a higher pressure of 6GPa, the corrosion resistance increases and the microstructure refining effect is not obvious. All the findings of this work were elucidated in terms of the change in the formation and growing of the crystal under a high pressure heat treatment condition.
Authors: Lai Lei Wu, Lin Liu, Mai Shun Qi, Jian Hua Liu, Rui Jun Zhang
Abstract: After heat treatment at 800°C for 15min, a Cu-Al alloy was cryogenic treated at -196°C for 30min, the micro-mechanical properties of the Cu-Al alloy before and after cryogenic treatment were measured by nanometer mechanical testing system and the microstructure of the Cu-Al alloy were also analyzed by optical microscope, SEM/EDS and XRD. On the basis of that, the effects of cryogenic treatment on micro-mechanical properties of the Cu-Al alloy were investigated. The results show that the cryogenic treatment can refine the grains, and increase the hardness, elastic modulus, elastic recovery rate and ratio of hardness to modulus of the Cu-Al alloy. As a result, cryogenic treatment can improve the ability to resist applied load and anti-indentation creep effectively.
Authors: Li Min Chang, Jian Hua Liu, Rui Jun Zhang
Abstract: Ni/Al2O3 composite coatings were prepared by direct current (DC), single pulse current (PC) and pulse reversal current (PRC), respectively. The hardness and wear resistance of the coatings were investigated and the morphology and elements distribution in cross-section were analyzed by the application of SEM/EDS, XRF and XRD equipped with stress measuring device. The results show that the hardness of the three kinds of coatings increase with increasing Al2O3 content. The coating prepared by PRC plating exhibits higher hardness and better wear resistance, while that of DC plating has lower hardness and poorer wear resistance. The higher hardness and better wear resistance of coating of PRC plating can be ascribed to fine microstructure and weaker stress between substrate and coatings.
Authors: Yu Wen Liu, Wei Lu, Jian Zheng Song, Jian Hua Liu, Rui Jun Zhang
Abstract: The influence of deformation on dechromization of CuCr alloy in H3PO4 solutions was investigated by static immersion corrosion tests. The properties of undeformed and deformed alloys were characterised by XRD, Metallograph, SEM and X-ray fluorescence spectrometer respectively. It is observed that the deformation plays an important role in dechromization of CuCr alloys in H3PO4 solutions. Compared with undeformed one, the deformed CuCr alloy’s incubation time of corrosion is shortened, the concentration and temperature of H3PO4 solutions needed for dechromization decrease. Consequently the tendency of dechromization increases. Surface analysis showed that the microstructure of the dechromization layer is scarcely influenced. Finally, the dechromisation mechanism was discussed.
Authors: Mai Shun Qi, Ya Li Li, Lai Lei Wu, Jian Hua Liu, Rui Jun Zhang
Abstract: The transformation temperature and time of α+γ2 to ß in a Cu-Al alloy after cryogenic treatment during heating were measured by DSC, and the transformation activation energy of α+γ2 to ß was also calculated. It is indicated that the Cu-Al alloy with heating rate of 10°C/min, the phase transformation onset and ending temperature is 561.75°C and 582.88°C, respectively, and the phase transformation time is126.6S. The phase transformation activation energy decreases with the increasing volume fraction of their phase transformation.
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