Papers by Author: Hong Gu

Abstract: The influences of Sn addition of 3%-30% on the friction and thermal expansion properties of Al-Sn bearing alloys were investigated in this paper. The experiments were carried out on a specially designed friction testing machine and a dilatometer. It is shown by the experiments that the friction coefficient and hardness of the alloys decrease with the increasing of Sn content. The friction coefficient decreases dramatically when Sn content is higher than 6%. On the other hand, the friction coefficient is also dependent on the load. The friction coefficient increases as the load rises. The linear CTE is also a function of temperature and Sn contents. CTE increases when the temperature rises but has no obvious differences for the alloy system when the temperature is below 80°C. As the temperature rises, the differences become large among the alloy system. The higher the Sn content, the lower the CTE.

Abstract: In this paper, a new low-pressure die-casting with degassing function, casting under adjusted pressure (CAP), is proposed. The working principle of CAP process is introduced in details. This paper focuses on the influences of moisture of compressed air on the hydrogen content within the melt aluminum during the cyclic vacuum-pressurizing programs for CAP process. The experimental results indicate that degassing under vacuum acts positive in refining aluminum melt. The relative moisture of compressed air exerts a significant influence on the hydrogen content of aluminum melt. After the melt aluminum is exposed to the air with a relative moisture of 85% for 90 min, the hydrogen content of the melt aluminum can get to 0.4 ml/100g/Al; while under the circumstance of CAP process, the hydrogen content is maintained between 0.05 and 0.15 ml/100g/Al depending on the moisture capacity of the air, which virtually has no more influence on the casting qualities. Under the condition of dry compressed air, the hydrogen content can be kept at a level as low as 0.05ml/100g/Al, which facilitates to obtain high air-tightness castings.

Abstract: In the present paper, TiB2/Al composite with 5% volume fraction of TiB2 was fabricated by LSM method. The effects of purification and degassing methods on TiB2/Al composite were examined by means of X-ray diffraction (XRD) and image analysis. Hydrogen contents in the molten composites were detected and compared among flux, inert gas and vacuum purification processes. The experimental results indicate that under general cast condition a majority of the TiB2 particles distribute on grain boundary, and only a few particles disperse within grains. The flux and vacuum purifications have no virtual impact on the distribution of TiB2 and the fraction of TiB2 remains the same after purification. However, degassing with inert gas will be detrimental; the TiB2 particles will be separated and removed from the matrix. The hydrogen contents for flux, inert gas and vacuum processes are 0.15ml/100g/Al, 0.12ml/100g/Al and 0.12ml/100g/Al respectively.