IN-SITU FORMATION OF TIB2 REINFORCED ALUMINUM VIA MECHANICAL ALLOYING

This paper investigates the possibility of in-situ formation of TiB2 c eramic particulates via the process of mechanical alloying of elementa l Ti and B powders in a system diluted with Al. Elemental Al powder wa s mechanically milled together with Ti and B powders in a high energy planetary ball mill. 30 stainless steel balls with diameter of 15 mm w ere employed. The ball to powder weight ratio was 20:1. X-ray spectra revealed the evolution of structural changes of the alloyed powder par ticles. No evidence of formation of TiB2 was manifested when the milli ng duration was shorter than 30 h. A TiB2-like structure could be dete cted only after 40 hour of milling. Because of broadening and weakenin g of the X-ray diffraction (XRD) peaks corresponding to Al and TiB2 st ructures as a result of refinement of crystalline size and the presenc e of large structural distortion, only very weak and vague TiB2 XRD pe aks could be detected. Clear evidence of formation of TiB2 was, howeve r, observed when the mechanically alloyed powder was annealed. Therefo re, the results of the present investigation clearly indicate that for mation of in-situ TiB2 particulates within Al is possible although a l onger milling duration is required. Mechanical testing shows that both the 0.2 % yield and the ultimate tensile stresses are increased with MA duration and sintering duration.