MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF TITANIUM CASTINGS

Precision casting is an attractive method for the net shape production of parts, particularly interesting for expensive alloys like titanium . This paper investigates the possibilities to improve the properties of titanium castings, solely applying thermal treatments. It was shown that in the (alpha+beta) titanium alloy Ti-6Al-4V, which is used for casting applications, the yield stress, the fatigue strength and the c reep resistance can be simultaneously improved by producing bi-lamella r microstructures where the beta phase is hardened by the precipitatio n of fine alpha lamellae. In titanium alloys with a lower volume fract ion of the beta phase, e. g. in the near-alpha alloy Ti-6242, localize d dissolution of beta lamellae may occur, which has a negative influen ce on the fatigue resistance while the yield stress and the creep resi stance are still improved.