Microstructures and properties of semisolid billet and thixo-forging product prepared by vibrating wavelike sloping plate (VWSP) process

Abstract

By using self-made vibrating wavelike sloping plate (VWSP) setup, the process of preparing semisolid billets of light alloys by semi-continuous casting and thixo-forging process were studied. Semisolid billets with fine spherical or rosette grains were prepared by the proposed process, and the solidified shell on the sloping plate surface can be effectively avoided. During the casting process, due to metal flow and vibrating, burst nucleation in the whole melt and dendrite fracture take place, which causes the formation of fine spherical microstructures. Casting temperature, vibrating amplitude, sloping plate length and sloping angle are the main factors influencing the alloy microstructure. Under the current experimental conditions, the proper casting temperature ranges of 660°C–680°C, the amplitude value smaller than 2 mm and the proper sloping angle ranges of 40°–60° are suggested. When the reheating temperature is 575°C and the holding time is 60 min for AZ91D alloy, and 597°C and 90 min for Al-6Si-2Mg (wt.%) alloy, the semisolid forging process can be successfully implemented. Thixo-forming products of such two alloys are fine with smooth appearance, good microstructures and properties.

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