Formation of Ultrafine-Grained Ti3Al on a Ti48Al2Cr2Nb Intermetallic Alloy Induced by Pulsed Electron Beam Treatment

Abstract

The microstructure modifications, phase, and texture formations encountered in a TiAl based Ti48Al2Cr2Nb intermetallic alloy induced by the high current pulsed electron beam (HCPEB) treatment were carefully investigated using scanning electron microscope (SEM), X-ray diffraction (XRD), and electron backscattered diffraction (EBSD) techniques. The initial material contains the majorityγ-TiAl phase and the minorityα-Ti3Al phase. After the HCPEB treatment, the initialα-Ti3Al was dissolved into the melted layer and the very top surface is covered by ultrafine-grainedα-Ti3Al phase having thermal stress induced cracks. EBSD analyses showed thatα-Ti3Al phase on the very top surface has a001//ND fiber texture and its texture intensity increases with the number of pulses. The superfast thermal stress cycles and the selective evaporation induced by the HCPEB treatment account for the microstructure modifications and formations of ultrafineα-Ti3Al in the TiAl based intermetallic alloy.