Siavash Zamani - Department of Materials and Metallurgical Engineering, Iran University of Science and Technology, Tehran, Iran
Hekmat Razavizadeh - Department of Materials and Metallurgical Engineering, Iran University of Science and Technology
Mohammad Jahazi - Department of Mechanical Engineering, Ecole de Technologie Superieure, Montreal, Canada

In the present study, to determine the influence of the Vanadium and Chromium additions on the deformation mechanisms of the TiAl based alloys, theoretical and experimental approaches were used. In one hand, the changes of electronic structure parameters in the lattice of ternary TiAl alloys were calculated by employing the discrete variational Xα cluster method. Calculations were set such to consider the ternary TiAl containing third alloying elements for about 2 at.% in the hypothetical composition. Parameters changes of the bond strength, the bonding anisotropy ratio and the lattice resistivity to the micro-deformations, by addition of V and Cr alloying elements were calculated and discussed. In the other hand, experimental tension tests were designed and carried out at ambient temperature on the standard samples of the Ti-48Al, Ti-48Al-2V and Ti-48Al-2Cr alloys which produced with the similar compositions to those calculated. Calculations results show that addition of V and Cr alloying elements to binary TiAl can increase the yield strength of the alloy by increasing the lattice resistivity to motion of preferred dislocations. Also, addition of both the Cr and V alloying elements results in improving the ductility of TiAl alloys by reducing the resistance of the lattice to motion of the l/2<110] ordinary dislocation and 1/2<112] superdiclocation relative to the <011] superdislocation which is in agreeing with the experimental results. Moreover, Results show that the Cr addition has more ductilizing effect on the binary TiAl compared to the V because of the fact that addition of Cr has a larger influence on nearing the tetragonal ratio to unity

TiAl, deformation mechanisms, discrete variational-Xα method, mechanical behavior, alloy designing