Study On Liquid Forging Of High Aluminum Zn-based Alloys Wear-resistant Parts

Because of its outstanding properties, the high-aluminum Zn-based alloy, as the substitutes for copper-tin alloy, has been a study focus on metal material since 1990s.In virtue of many properties, such as excellent flowing property, processability, higher mechanical performance, various process operation and the best high-temperature behavior among all of Zn-Al alloy, ZA27 alloy is now given a special attention during the research and development of the high-aluminum Zn-based alloy.Forming experiment on liquid forging technology of ZA27 alloy was studied in this paper. Using hat-shaped die and wear-resisting underboarding die, the precision semi-finished product was obtained. The effect of different process parameters (point of pouring, specific pressure, time of pressure maintaining, preheat temperature of die, etc.) on microstructure and performance has also been studied. Furthermore, influencing factors on surface quality and dimensional accuracy of the drip molding and shaped mechanism of liquid forging have been discussed. Mechanical properties and wear-resisting property tests were used on ZA27 alloy drip molding by sand casting metal mould casting and liquid forging, wear mechanics has been analyzed, the relation between wear-resisting property and forming technology has been indicated.Because of the wide interval of freezing temperature, ZA27 alloy can easily give birth to dendritic structure and shrinkage porosity during its freezing course. The experiment indicated that liquid forging technology can give birth to dense structure and reduce flaws to a great extent, so the mechanical properties of drip molding are better than sand casting and metal mould casting.Point of pouring, specific pressure, time of pressure maintaining and preheat temperature of die are the key process parameters of liquid forging, which direct affect the mechanical properties, surface quality and the die life and its service performance. The experiment result indicated that wear-resisting underboarding drip molding can represent dense structure, excellent mechanical properties and wear-resisting property in this condition: specific pressure is 50-60MPa,forcing speed of upper die drift pin is 20-40mm/s, time of pressure maintaining is 30-50s, Point of pouring is 590-630℃, preheat temperature of die is 250-300℃.