Study On Preparation And Properties Of Si_p/ZA40 Composites

In this paper, the Si_p/ZA40 composites was fabricated by melting method using ZA40 alloy (matrix material), aluminum-silicon alloy (silicon carrier) Zinc as the raw materials. The microstructure, phase and mechanical properties of the alloys were studied by using X-ray diffraction, scamming electronical microscope, optical microscope, impact, hardness, wear, and tensile anaysis, respectively. The main results are as follows.The Si_p/ZA40 composites was fabricated using gravity casting technique with sodium salt as modifier. The results indicated that the size of silicon particle in the composites was influenced by pouring temperature and silicon content. The size of silicon particle increased when the pouring temperature decreased at the same silicon content. And when the addition content of silicon increased at the same pouring temperature. The Si_p/ZA40 composites was obtained with regular, fine and uniform distribution silicon particle by adding 4.5wt% silicon and pouring at 700℃.The amount of primary silicon and the irregular particles increased when the addition content of silicon increased. And the mechanical properties of the composites decreased because of the laceration of primary silicon in the matrix. But the hardness of the composites increased by increasing silicon content and the size stability improved at 150℃and at room temperature. The fracture type of the composites included plastic and brittle fracture.The wear resistance of Si_p/ZA40 composites was investigated under the conditions of dry friction and oily lubrication. The results show that the wear resistance of the composites was better than that of the matrix materials and the wear resistance increased when the applied load increased. The wear resistance of the composites was superior to the matrix materials when the load was big under oily lubrication, but it was not satisfactory under dry friction conditions. High aluminum Zn-based alloys exhibited excellent wear properties under low speed and overload conditions and it was not suitable to work under dry friction conditions. The wear resistance of the composites depended on the silicon content and the composite with 4.5wt% silicon had the best wear resistance. The wear mechanism of the composites was the function of micro-cutting,adhere and grain wear.The wear resistance was studied by comparing the ZA40-4.5%Si composites with tin bronze. The wear resistance of the composites was found to be superior to the phosphor bronze in all test conditions. The wear resistance of the composites was better than the phosphor bronze under oily lubrication and overload conditions. The phosphor bronze was suitable for working under low load. But the ZA40-4.5%Si composites still show good wear resistance under high load. Thus, the application of ZA40-4.5%Si composites was wider than that of phosphor bronze.