Abstract
Structural modification of nanocrystalline trialuminde Al3V by microalloying with Ti and macroalloying with Zr was studied. For micro and macroalloying, the Al75(VxTi1−x) x = 0-25 and Al5ZrV2 were synthesized by mechanical alloying of elemental blends of the nominal composition. The structural changes of powder particles during mechanical alloying were investigated by x-ray diffraction patterns. Microstructure of powders was characterized by scanning electron microscopy and the hardness of powder particles was determined by Vickers microhardness measurement. It was found that microalloying of trialuminides by Ti led to the formation of Al3(V,Ti) with stable tetragonal structure (DO22) in different amounts of Ti after 40 h milling. Thermodynamic calculations, which were based on Miedema model, showed that the higher negative formation enthalpy of intermetallics in Al-V-Ti system induced refinement of trialuminides. In addition, it was found that the hardness of compounds was increased by enhancement of Ti in trialuminide composition. For Al5V2Zr compound, the metastable L12 phase was formed after 20 h milling. Thermal analysis of the synthesized compound showed an exothermic peak around 550 °C, which was related to the partial transition of L12 structure to DO22. Moreover, ordering of L12 phase took place due to increasing temperature.
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