Consolidation of nano-crystalline titanium carbonitride powders

Abstract

This article describes the basic idea that process control of electric discharge consolidation makes it possible to obtain fully dense high-strength nano-intermetallics. This powder processing provides sensors of pulse discharging and densification for making a process model and a control methodology. The discharging of rectangular pulses, monitored by voltage wave, is characterized by spark and arc, resulting in the neck formation between spherical amorphous particles. Then, densification of the amorphous Ti50Al50 powder under an electrical field is expressed by an Arrhenius-type equation of viscous flow: ηp=ηp0(I)exp{H(I)/kT}, where ηp is process viscosity. A mechanism of bulk transport via enhanced viscous flow through artificial multiple necks accounts for rapid pore-free consolidation. For ductile nano-intermetallic Ti50Al50 synthesized via crystallization, the highest specific strength is 790 MPa Mg m−3 at the γ grain size of 17 nm; and the softening temperature is comparable to those of cast TiAl and Ni-base superalloy.