Powder Metallurgical Manufacturing of Ti-Nb alloys Using Coarse Nb Powders

Powder metallurgy is an attractive method for cost effective production of near net shape Ti-Nb alloys, and, when elemental powders and coarse HDH powders are used, a higher flexibility in alloy composition and low processing costs can be achieved. In this study, manufacturing of (α+β) Ti-Nb alloys by powder metallurgical techniques using coarse HDH Nb (D₅₀= 110 μm and D₅₀= 255 μm) and HDH Ti (D₅₀= 22.6 μm) powders as starting materials was described. Tape casting was applied for the production of porous sheets while warm compaction of Metal Injection Molding (MIM) feedstock was applied for the production of dense parts. Microstructural and mechanical tests were employed to investigated the effect of coarse Nb powders on the sintering behavior and mechanical properties. Tape casting enabled to produce porous sheets of Ti16Nb alloy with an interconnected porosity varying from 14 - 31 vol.%. Warm compaction enabled to produce Ti-Nb parts with less than 2% porosity and Yield strength in compression of 975-1100 MPa, which is similar to the values reported for Ti-Nb based alloys produced by powder metallurgy of finer powders. A dynamic Young’s Modulus of 37-52 GPa, significantly lower than that of cp-Ti was achieved. These results might provide guidelines for the use of coarse Nb powders as starting materials for the powder metallurgical development of low-cost Ti-Nb based alloys.

Keywords:
Sintering; Ti-Nb alloys; MIM; tape casting