Hao Jianmin

Microscopic Characterization of Semi-Solid Ti14 Alloy

The microstructural evolution and the element distribution of Ti14 (a+Ti2Cu) alloy during semi-solid compression were investigated. Moreover, the Ti2Cu precipitate behaviors were discussed in detail. The results show that the microstructure, the number and distribution of Ti2Cu precipitates have significant dependence on the process parameters. More Ti2Cu will precipitate on grain boundaries at a higher deformation temperature, and/or a lower strain rate as well as deformation ratio, and finally a network structure is formed after deformation at 1100 °C. The precipitation on grain boundaries is found to be mainly controlled by peritectic reactions. The elevated temperatures resulted in more liquid along the prior grain boundaries, and a Cu-rich region is formed, finally. the “coarse” grain boundaries appear during re-solidification.

Surface Strengthening of Ti-6Al-4V Alloy by Glow Plasma Carbonization Process

Abstract A glow plasma carburizing technique was applied to strengthen the surface of the Ti-6Al-4V alloy. The alloy was carburized at 950 °C and 30∼35 Pa for 3 h using plasma of Ar gas. Graphite rod was employed as carbon supply to avoid the hydrogen brittleness which is common in traditional gas carbonization. The carburized layer was examined by an optical microscope (OM), field emission scanning electron microscope (FESEM), and X-ray diffractometer (XRD). The wear resistance under ring-block wear testing and the surface hardness were evaluated and compared to those for the untreated material. Results show that a carburized layer (416 μm thick), mainly composed of TiC and V 8 C 7 , is found. These hard carbides contributed to the imrovement of the hardness and wear resistance.

Influence of Processing Parameters on the Deformation Behavior of Ti14 Alloy Containing a Small Volume of Liquid

Abstract The effects of the processing parameters on the deformation behavior of Ti14 alloy containing a small volume of liquid have been investigated through compressive tests. Experiments were conducted at deformation temperatures from 1000 to 1150 °C, strain rates from 5×10−3 to 5 s−1 and deformation degrees from 40% to 70%. The results show that deformation temperature and strain rate have significant effects on the peak flow stress. The flow stress decreases with increasing of deformation temperature and/or decreasing of strain rate. The response time required by deformation is affected by the strain rate and liquid fraction is controlled by the temperature. As the temperature increases, deformation mechanism transforms from sliding between solid particles (SS) to the flow of liquid incorporating solid particles (FLS), which improves the semi-solid deformation behavior. In addition, the flow stress decreases with increasing of deformation degrees during the compression which is associated with lubricating effect of liquid during semi-solid deformation.

Design of Micro-oxidation power control system based on LPC2119

MAO (micro-oxidation) is a surface process technique which makes ceram layer grows in the original position of the surface of metal. A self-developed micro-oxidation power control system was introduced in this paper. The hardware part composed of low consumption 32-bit microcontroller LPC2119 developed by Philips Company instead of MSC 51 single chip, which enhanced the stability and extensibility of system; while the software design adopted uC/OS-II multitask type instead of the traditional forward and backward design type, which enhanced the precision and real-time response of the system. Parameters can be set the same as PC, and preset functions can also realized in this system. We have used the PID control way in the system.. In addition, large scale adjustment of voltage, current, pulse frequency and duty ratio can also be satisfied. The developed system has been applied in products, leading to well effects.