A Comparison between the Effect of Cr and W Addition on Formation Kinetic of Nanostructure TiAl(γ) Alloy by Mechanical Alloying Route

Abbasi Nargesi, F.; Azari Khosroshahi, R.

A Comparison between the Effect of Cr and W Addition on Formation Kinetic of Nanostructure TiAl(γ) Alloy by Mechanical Alloying Route

Document Type : Research Paper

Authors

F. Abbasi Nargesi

R. Azari Khosroshahi

Matrials Engineering Faculty, Sahand University of Technology, Tabriz, I. R. Iran

Abstract

In this research, mechanical alloying was used to produce Ti-50Al, Ti-45Al-5Cr and Ti-45Al-5W (at%) alloys. The effect of ternary addition (Cr and W) on microstructure and production efficiency of TiAl alloy were investigated. Alloying was performed in a planetary mill and the milling time varying from 5 to 70h. The structural evaluation in these powders was done by X-ray diffraction (XRD) technique and Scanning Electron Microscopy (SEM) during mechanical alloying and after annealing at 1100°C in vacuum oven. The results showed only a complete amorphous phase after 50h of milling of Ti-50Al powder mixture, but with 5at% addition of Cr, the Cr (Ti, Al) solid solution within the amorphous matrix were identified after 70h milling and with 5at% addition of W, the W lattice was remained with amorphous phase. The time required for solid solution or amorphous phase formation was longer in Cr and W containing powders. After annealing of mechanically alloyed Ti-50Al, the γ-phase with high purity and nanostructured size was produced and for sample with Cr addition, the TiAl(γ) with amount of Ti3Al(a2) were formed and for sample with W addition, the duplex phase (γ+a2) with a minor amount of W, were formed.

Keywords

Mechanical alloying

Titanium Aluminide

Chromium

tungsten

nanostructure