Synthesis of Nanostructure Ti-۴۵Al-۵Cr Alloy by Mechanical Alloying and Study the Effect of Cr Addition on Microstructure of TiAl Alloy

In this work, mechanical alloying was employed to produce Ti-۵۰Al and Ti-۴۵Al-۵Cr (at%) alloys. Alloying was performed in a planetary mill and the alloying time varying from ۵ to ۷۰h. Characterization of the powder mixture was performed by X-ray diffraction (XRD), SEM analyses and DTA test, during mechanical alloying and after annealing at ۱۱۰۰°c in vacuum oven. The results showed, after ۵۰h of milling of TiAl powder mixture, only a complete amorphous phase was detected but with Cr addition (۵at%) the Cr (Ti,Al) solid solution within the amorphous matrix were identified. After annealed of mechanically alloyed Ti-۵۰Al for ۵۰h, the γ-phase with high purity and nanostructured size was produced but for sample with Cr addition, TiAl(γ) and amount of Ti۳Al(alpha۲) were detected. Cr accelerated the production of duplex structure (gamma+alpha۲). It suggested the Cr(Ti,Al) solid solution was dissolved in TiAl(gamma) and Ti۳Al(alpha۲).

Keywords:

Nanostructure , TiAl , Chromium , Ti۴۵Al۵Cr , mechanical alloying