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 mere 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 ph ase equilibrium. However, second phase particles of the size below 10 nm we re present especially in the Zr-rich alloys. They precipitated preferential ly in a fan-shape morphology and electron diffraction identified most of th em to be formed by the metastable Al-3(ZrxTi1-x) phase with the cubic L1(2) structure. The grains of the Ti-rich alloys were nearly free of such parti cles. The coarse particles present in the Ti-rich alloys were mostly consti tutional particles in the spectrum of which Fe was found. The microhardness values were found much higher in the Zr-rich alloys. A correspondence betw een microhardness and solidification microstructure and phase composition w as found.