Structure and properties of melt-spun Al-Zr-Ti alloys. II. The solidification microstructure and microhardness

Thin ribbons of the Al-Zr-Ti alloy with variable Zr:Ti ratio were prepared using the melt spinning method. The solidification microstructure was found to be inhomogeneous along the direction perpendicular to the ribbon plane and dependent on the Zr:Ti ratio. The phase composition was far from the phase equilibrium. However, second phase particles of the size below 10 nm were present especially in the Zr-rich alloys. They precipitated preferentially in a fan-shape morphology and electron diffraction identified most of them to be formed by the metastable Al sub 3 (Zr sub x Ti sub 1-x ) phase with the cubic L1 sub 2 structure. The grains of the Ti-rich alloys were nearly free of such particles. The coarse particles present in the Ti-rich alloys were mostly constitutional particles in the spectrum of which Fe was found. The microhardness values were found much higher in the Zr-rich alloys. A correspondence between microhardness and solidification microstructure and phase composition was found.