Gamma titanium aluminide refers to a group of alloys of titanium with a distinct composition containing long-range ordered structures. This, along with strong interatomic bonding means that they have high temperature strength and low density as well as good corrosion resistance. However, as they are brittle at room temperature, they are very hard to machine. Gamma titanium aluminides contain titanium and aluminium as well as a number of alloying elements such as chrome, iron, manganese and niobium in varying amounts.
MBN have determined a range of possible powder compositions based on the requirements of the different case-study parts. They have produced small batches of powder for the additive manufacturing machine using high energy ball milling. Factors to take into account are the process yield and the characteristics of the resultant powders, including particle shape and size distribution. The powder microstructure strongly influenes the mechanical properties of additively manufactured parts built using this material.
To reduce the cost of the powder, one of the project objectives, a trade-off must be made between the cost and quality of the raw materials used and the effect on the powder produced, so a trade study has been carried out to determine the sensitivity of the final material to the quality of the base elements.
Powders in the correct size range are selected by sieving the material from the ball mill. To further reduce costs, methods of recycling the unused material have been developed, which increased the yield by 15 percentage points. The material formulation will be refined after additive tests have been carried out and the result material properties determined.