Microstructure and mechanical properties of Ti-B-N cast alloys prepared by reactive arc-melting

Ti-B-N cast alloys were prepared by a reactive arc-melting technique using elemental titanium and boron nitride powders. The alloys obtained were composites of titanium matrix containing nitrogen of 3 mol% or less and a small amount of TiB reinforcement. The microstructure of the matrix was a cellular structure consisting of elongated dislocation cells with 1-2 μm in width and 5-10 μm in length, for Ti-1B-1N alloy. The TiB particles were rod-like in shape with size of less than 0.5 μm in diameter and agglomerated to form clusters along the grain boundary. The mechanical properties were mainly dependent on the content of nitrogen and the influence of TiB on the mechanical properties was relatively small. The Ti-B-N cast alloys containing suitable concentration of nitrogen, Ti-0.5B-0.5N alloys, had a high strength of 920 MPa with adequate ductility of more than 5%.