Microstructure and Mechanical Properties of Cast Composites of Steel Wool Infiltrated by Magnesium and AZ91 Alloy

Abstract

In the present study, composites have been synthesized by infiltration of 0.15 wt% carbon steel wool by molten magnesium and AZ91 alloy, which solidifies by cooling under vacuum. The microstructure of the composites observed on a plane normal to the direction of flow shows the transverse section of steel wool strands mostly and clustering of these strands due to pushing by stream of melt during infiltration. The composite based on AZ91 alloy shows network of precipitates of Mg₁₇Al₁₂ along the boundaries of dendrite cells in the matrix, which are significantly finer compared to that in the cast AZ91 alloy. The microhardness of the steel wool in the composite increases with increasing steel wool content, which has been attributed to increased restraining influence of steel wool at higher steel wool content on the plastic flow of the surrounding matrix. The ultimate tensile strength (UTS) is higher in the AZ91 alloy-based composite compared to those observed in the composites based on commercial magnesium, at comparable steel wool content, and the strength increases with increasing steel wool content although densities of the composites increases as well.

Keywords:

• AZ91 alloy
• Composite
• Magnesium
• Steel wool