TiN formation in the TiH2-B system during reactive mechanical alloying to produce Ti-TiN-TiO2-TiB metal-matrix composites


Ozbilen S.

7th International Symposium on Processing and Fabrication of Advanced Materials VII, Illinois, United States Of America, 11 - 15 October 1998, pp.257-266 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Volume:
  • City: Illinois
  • Country: United States Of America
  • Page Numbers: pp.257-266

Abstract

Reactive mechanical alloying of TiH2-B powder mix for ten uninterrupted hours with sealed vial was carried out under nitrogen and air together with MA under purified Ar for comparison. Powder samples MA'ed under different atmospheres were then examined by EDAX analysis for their oxygen and nitrogen contents. This was followed by annealing of MA'ed powders under purified Ar to 1200 degrees C for thermal treatment to determine the stability of nitrides and oxides plus inter-metallic compound (i.e., TiB) forming. Representative samples of each powder MA'ed and thermally treated were characterized by XRD using Cu K alpha radiation and examined by Cambridge ST40 Stereoscan SEM operating under 25kV to determine morphology and crystal structure change of the powders. It is observed that RMA cause to the formation of TiN when it is carried out under N-2; to that of (Ti,O)N with RMA under air. The f.c.c. (Ti,O)N phase forms as a result of the preferential reaction of nitrogen with Ti to form TiN with which any oxygen present can then react to form (Ti,O)N. This indicates reversed reaction kinetics of Ti with oxygen and nitrogen during RMA. MA under purified Ar prevents the formation of any Ti-nitride or Ti-oxy-nitride. Annealing under purified Ar to 1200 degrees C for one hour leads to the formation of Ti-TiN-TiB multi-phase material in powder mix RMA'ed under N-2; to that of Ti-TiN-TiO2-TiB with RMA under air; and only Ti-TiB with MA under purified Ar. This shows that sintering of the MA'ed powders is a promising way for producing ultrafine grained metal-nitride-boride composite materials with RMA processing under N-2; metal-nitride-oxide-boride CM's with RMA under air, and finally metal-boride CM's with MA under purified Ar of TiH2-B powder mix.