Microstructural Modification of Al–30Si–5Fe Alloy Using a Combination of Rapid Solidification and Thixoforming Processes

Abstract

It is commonly known that the properties of materials are strongly related to their microstructure. This paper introduces a method that is a combination of rapid solidification (melt spinning) and semisolid forming (thixoforming) processes, which are used to refine the microstructure of “as-cast” Al–30Si–5Fe alloy and improve its mechanical properties. Produced Al–30Si–5Fe ribbons by melt-spinning process, were pulverized and subsequently consolidated at 300 °C in argon atmosphere. Prepared specimens were thixoformed at temperatures ranging from 580 to 700 °C in various holding times. Some samples were also directly thixoformed from as-cast condition. Microstructure of the as-cast, meltspun, and thixoformed samples were investigated in each stage of manufacturing procedure. In all thixoformed samples, microstructures were modified, and needle-like intermetallic compounds as well as silicon particles in the as-cast part were changed into rounded corners or multifaceted structure with uniform distribution. The average size of hard particles significantly reduced from 160 μm in the as-cast condition to 3–30 μm in the meltspun-thixoformed samples. Finally, hardness test was carried out to evaluate specimens. In comparison with the as-cast condition, results showed 23–94% increase in hardness for meltspun-thixoformed samples and 12–29% for cast-thixoformed samples.