Relations entre la microstructure et les propriétés mécaniques à froid des alliages de titane

The influence of microstructure on the room temperature mechanical properties of titanium alloys

O.N.E.R.A.

Abstract

The influence of the main microstructural parameters on the low temperature mechanical properties of Ti alloys are reviewed. In the case of α alloys the strength depends of grain size, solid solution hardening and precipitation or dispersion hardening ; it is shown that Ti₃Al containing alloys are brittle when α₂ is sheared by the moving dislocations. In α + β alloys a wide variety of α and β morphologies can be obtained. It is emphasized that only the fracture touhgness is strongly dependent on the acicular or equiaxed shape of the α grains ; the ductility is a decreasing function of the primary β grain size. In actual applications the possibility of playing on the cristallographic texture can be of interest.

The various decompositions of metastable β alloys in β + ω, β + β' and β + α are described and the fragilizing role of ω briefly sketched.