Al-X (X=Nb, Cr, Fe) Ultra-High Strength In-Situ Composite Wire

Abstract

Cast and deformed microcomposites such as Cu-Nb multifilamentary composites have been reported as ultra-high strength wires which exhibits anomalous increase in tensile strength with heavy deformation. To apply this procedure to aluminum based wires, powder metallurgy process is an attractive alternative to avoid interfacial reaction between chemically reactive Al and secondary elements. The present study is aimed at fabrication of such a heavily deformed in-situ composite wire based on Al and evaluation of its mechanical properties. Tensile strength is of particular interests, especially from the viewpoint of relationship with microstructures. Al powder and Nb powder are mixed, uni-axially pressed, and swaged with two restacking steps employed to obtain high drawing strain. All processes including the pressing are performed in room temperature air. Metal filaments get finer and closer together as the drawing strain increases, and uniformity of the filament distribution also increases with deformation. Tensile strength increases to 1063 MPa at drawing strain of 14.6, which is the maximum drawing strain in this study. The dependence of ultimate tensile strengths of the composites on the mean filamentary spacing is investigated. There is a good correlation with the Hall-Petch type relationship. This result suggests that the filaments acts as barriers against dislocation motion, and that shear modulus of the second phase barrier is a predominant parameter for the strengthening of the wire.