Study Of The Effect Of Silicon And Magnium On Properties Of High Aluminum Zinc Matrix Alloys

ZA27 alloy-one of the most widely used ZA series alloys-is studied in this paper. In actual engineering applications, its wear resistance reduces due to the high temperature resulted from the continuous and heavy load service, which cannot fit the demand of engineering applications. Based on the recent research throughout the world, in order to improve mechanical properties and wear resistance at high temperature of ZA27 alloy, Si and Mn are added to modify its microstructure. Its microstructure and mechanical properties are tested and the sliding friction at ambient temperature and sliding friction at high temperature of ZnAlSi and ZnAIMn are studied.Alloys are melted in intermediate frequency furnace and Graphite crucible respectively. Si and Mn are alloyed to improve properties. Through SEM, metallographic microscope and Electronic probe microscopical analyzer, the microstructures of the alloy are studied and the properties are analyzed.Results show that the high aluminum zinc base alloy ZA27 alloyed by Si has an overall higher hardness and tensile strength; Mn can improve alloy's hardness and at the same time reduce the elongation. When the content of Mn is 1.5wt. %, the hardness of the alloy is the highest but the elongation lowest. The premium content of Mn is about 0.4-0.8wt.%; Under the tensile stress, the fracture mode of ZA27 alloyed with Si or Mn is a mix type fracture- the plastic fracture and the brittle fracture are coexistence. Cracks are mainly stemmed from brittle phases of Si and Mn and develop along the grain boundary. When lightly loaded, the sliding friction resistance (at ambient temperature) of ZA27 alloyed with Si is no better than that of common ZA alloy. But when heavyly loaded, the former is far better than the latter. The wear resistance of ZA27 alloyed with Mn is no obviously better than that of common ZA27 alloy. Under the sliding friction conditions, the wear resistance at high temperature of ZA27 is improved by alloyed Si and reaches the highest level when the content of Si is 1-3wt.%. And also, the wear resistance at ambient temperature and of ZA27 alloyed with Mn when lightly loaded is desirable but becomes worse at high temperature. The wear mechanism of the one mixed with both adhesive and abrasive wear under sliding friction conditions (at high temperature).