Researchers in The Netherlands are investigating Beta titanium alloys that exhibit toughness properties similar to transformation-induced plasticity (TRIP) steels. Their intention is to use this material in applications such as aeroplane landing gear, which faces heavy loads and demanding fail-safe applications, but could benefit from a lighter material. The team at the Delft University of Technology spent three years creating a thermodynamics-based model to predict the martensite start temperature of the beta alloys. Using this model, the group says it has transformed the metastable beta phase of a 10-2-3 alloy (Ti-10V-2Fe-3Al) to a martensitic phase. This increases its failure load by 30%. The technology used is similar to the phase transformation that occurs during the straining of TRIP steel. The material usually consists of ferrite, bainite, martensite components and restrained austenite. Straining causes the austenite to transform into martensite. This increases the overall strength of the steel. The concept is based on heat treatment to destabilise the beta phase alloy. This involves a redistribution of the solute atoms (to the point where) the destability gets the best effect during straining at room temperature. The effect can be switched on or off by choosing a higher or lower temperature. The group is collaborating with roller bearing company SKF and Tata Steel to further develop the alloys.
