Papers by Author: Zhen Liang Qiao

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Authors: Yue Ying Li, Qi Chao Deng, Ping Shi, Zhen Liang Qiao
Abstract: Two kinds of surface heat treatment (wide-band laser surface quenching and high-frequency induction quenching) had been performed on a ferrous PM cam material for automobile applications. Microstructure, hardness and tribological properties of ferrous PM cam materials were investigated. After laser surface quenching, the sintered cam materials could obtain finer martensite microstructure and higher hardness value, compared to high-frequency induction quenching. Wear tests revealed the superior wear resistance and coefficient of friction of laser surface hardened specimens in comparison with high-frequency induction quenched ones. Laser surface quenching can be a more effective surface heat treatment to improve wear resistance of the sintered cam materials than high-frequency induction quenching. On the lower test loads (such as 50N), the wear mechanism of the surface quenched ferrous PM cam materials is dominated adhesive and abrasive wear, while on the higher test loads (such as 120N and 150N), it is primarily delamination wear and abrasive wear.
Authors: Yue Ying Li, Fu Wen Zhu, Zhen Liang Qiao
Abstract: TiB2 particulate reinforced titanium matrix composites were prepared by mechanical alloying and spark plasma sintering. Volume fraction of TiB2 powders in the composites are 5%, 10%, 15%. The effect of milling time and the volume fraction of reinforcement on microstructure and properties of the composites were studied. The results show that with increasing milling time, the size of powder particles decreases, quantity of them increases, and microstructure of the sintered samples becomes finer and more uniform. When milling time reaches 30h, the trend of powder agglomeration increases, the downward trend of the particle size becomes slowly. With the milling time, the density of titanium matrix composites is on the rise. The density of 10vol%TiB2 particulate reinforced titanium matrix composites can reach 4.799 g/cm3, with 30h milling time and sintering at 900°C. The density and hardness of the composites increase with increasing the volume fraction of TiB2. When the volume fraction of TiB2 is 15%, after milling 10h and sintered at 800°C, the density and hardness of the composites can reach 4.713g/cm3 and HV851.58.
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