Fabrication of nanostructured TiAl-Mn based intermetallics by a thermomechanical powder process

초록

A thermomechanical powder process approach was made to produce a nanometer-sized grain structure in a titanium aluminide based intermetallic compound. The process was made up of reactive synthesis of elemental powder mixture, intense plastic straining by cold rolling and subsequent vacuum hot pressing. The alloy composition studied was Ti-43.5at%Al-1.6at%Mn-2vol.%TiB2, and the starting materials were a commercially pure titanium powder, a gas atomized Al-3.6at%Mn alloy powder and a fine TiB2 particulate. These powders and particulates were mixed in the necessary ratio using a V-type mixer, and canned in an aluminum container to degas, and then the degassed mixtures were consolidated by extrusion. Reactive synthesis of the extruded mixtures was performed in a tube furnace under Ar atmosphere. The maximum temperature during the reactive synthesis was set up to 1593K, by which a titanium aluminide can be obtained. After the reactive synthesis, severe plastic deformation through cold rolling (80% reduction rate) and subsequent vacuum hot pressing at 1423K for 0.5h were carried out in order to refine the grain structure of the titanium aluminide to several hundred nanometer-sized ranges. The value of Micro Vickers hardness for the nanostructured titanium aluminide was determined to about 5GPa, which was about two times higher compared to the case of the titanium aluminide having the grain size of 50μm.