STUDY OF Ti-Al B ASED ALLOYS

Abstract

Elemental powders of AI and Ti with compositions, AI-(20, 40 and

60wt.%) Ti with the same amount of n-heptane were mechanically alloyed in ball milling "Attritor". Milling was carried up to 120-130 hours for the first two systems while for the third one to 90 hours, in an inert atmosphere at room temperature. X-Ray Diffraction (XRD), Optical Microscope (OM), Scanning Electron Microscope (SEM) and Differential Thennal Analysis (DTA) characterized the alloyed systems. The powder particles of Ti and AI interact with each other forming AhTi and Ti 3AI intermetallic. Mechanochemical reactions took place between metals and

liquid heptane, where the reactivity was enhanced by dry pre-milling of the metals powders for SOh. The heptane decomposed into carbon and hydrogen, forming f.c.c. TiC, and AhTi.tC2 . The hydrogen that is released as another product of n-heptane decomposition could have some effect on the alloying process. However, there is no hydride phase was observed by XRD, possible hydride phase fonnation in a small quantity can not be excluded to occur during milling. While AI3Ti and Ti3Al intermetallic did not react with carbon or hydrogen. From the change in the lattice parameter of AI after SOh ofMA (AI-20wt.%Ti), the solubility ofTi in AI could be estimated to be3.2at.%Ti. With the progression of the milling time, the particle size was effectively reduced and the grain size becomes in the nanoscale. The XRD patterns showed that, the Ti concentration plays an important role for the system amorphization, where the amorphous phases were seen to be more rapidly formed with increasing Ti content. It is possible to say that, at the final stage, one might have an in-situ composite in amorphous base.