Nb Doping Effects on Formation Mechanism and Structural Characteristics of Nanostructured Ti₅Si₃

Abstract

Nanocrystalline (Ti,Nb)₅Si₃ intermetallic compound was successfully synthesized by mechanical alloying of Ti_62.5-xNb_xSi_37.5 (X = 0, 10, 20) powder mixtures. The structural changes of powder particles during mechanical alloying (MA) were studied by X-ray diffraction, scanning electron microscopy, and microhardness measurements. It was found that a microstructure containing Ti/Nb/Si particles was formed in the early stages of MA followed by dissolution of Nb in Ti and gradual formation of disordered (Ti,Nb)₅Si₃ intermetallic compound having a nanograin structure. Annealing increased the D8₈ ordering in all samples. It was found that the long range order (LRO) parameter of intermetallic compound decreased with increasing Nb content. Also, after 45 h of MA, the microhardness of Ti_52.5Nb₁₀Si_37.5 powder mixture increased to 1325 HV. It was also increased continually by increasing the Nb content of the compound.

Keywords:

• Doping
• Intermetallic
• Milling
• Nanostructure