Amorphous powders of Al-Hf prepared by mechanical alloying

The authors synthesized amorphous Al50Hf50 alloy powder by mechanically alloying an equimolar mixture of crystalline powders of Al and Hf using hexane as a dispersant. The powder is characterized as a function of mechanical alloying time by scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry. Amorphous Al50Hf50 powder heated at 10 K s-1 crystallizes polymorphously at 1003 K into orthorhombic AlHf (CrB type structure). During mechanical alloying, some hexane decomposes and hydrogen and carbon are incorporated into the powder. The hydrogen can be removed by annealing the powder in vacuum below its crystallization temperature. The amorphous compacts have a diamond pyramid hardness of 1025 DPH.