Mechanically milled and reactively sintered Ti-Al compacts used for production of TiAl based IMC's


Ozbilen S.

7th International Symposium on Processing and Fabrication of Advanced Materials VII, Illinois, Amerika Birleşik Devletleri, 11 - 15 Ekim 1998, ss.267-277 identifier identifier

  • Yayın Türü: Bildiri / Tam Metin Bildiri
  • Cilt numarası:
  • Basıldığı Şehir: Illinois
  • Basıldığı Ülke: Amerika Birleşik Devletleri
  • Sayfa Sayıları: ss.267-277

Özet

Elemental powders of Ti and Al were mixed to get Ti-8 at % Al and Ti-53at % Al powder mixtures before mechanical milling. TiAl (gamma) powder produced by are-melting of pure Al and Ti is also mechanically milled before pressing. These mechanically milled powder samples, i.e., commercial purity Ti powder, Ti-8 at % Al and Ti-53 at % Al powder mixes and TiAl (gamma) compound powder were pressed to obtain compressed pellets. Afterwards, these pellets were not only vacuum annealed up to 720 degrees C but also reactively sintered at 1020, 1070, and 1135 degrees C under vacuum. As-received, as-mixed, mechanically milled, pressed, annealed, and reactively sintered samples of experimental materials were characterized by XRD and SEM investigation. In addition, elevated temperature micro-hardness measurements were also carried out. It was observed that liquid phase reactive sintering between molten Al and Ti results in incomplete synthesis and swelling in mechanically milled, pressed and sintered Ti-53 at % Al powder mix due to the presence of unreacted Ti in the structure after reactive sintering process thereby leading to the formation of a multi-phase, porous compact of TiAl(gamma)-Ti IMC material. Elevated temperature hardness values of Ti-53 at % Al sintered compacts were lower than those of 100% TiAl (gamma) compound compacts regardless of the sintering temperatures used indicating the presence of unreacted Ti thereby causing observed lower values of high temperature hardness values. This brings in the possibility of workability of TiAl (gamma)-Ti IMC material. However, as sintering temperature is increased, hardness increases due to the further formation of TiAl compound by reactive sintering and therefore ductility and workability of this IMC material becomes difficult. Since lower sintering temperatures results in less TiAl formation due to the incomplete synthesis reactions, these temperatures are advantageous in terms of room temperature ductility of the IMC material investigated in the present work.