Directionality in structure-property relationships: aluminium and titanium alloys

Mechanical properties are influenced by direction of testing with respect to wrought microstructure. In aluminium alloys the properties most sensitive to direction are ductility, fracture toughness, and stress corrosion and this can be attributed to the well developed mechanical fibring that exists in these alloys. Crystallographic textures are developed, particularly in extrusions, and some useful enhancement of strength is achieved in the longitudinal direction. Nevertheless, from a general viewpoint mechanical fib ring produces the predominant effects. Directionality of properties in α and α + β titanium alloys results primarily from the elastic and plastic anisotropy of the hexagonal lattice a-phase. Directionality effects are discussed, including those exhibited by the fatigue, tensile, fracture toughness, creep, stress corrosion, and sustained load properties. The important benefit of plastic anisotropy in terms of texture strengthening is highlighted, and it is concluded that optimum properties in α and α+β titanium alloys will be obtained by exploiting favourable textures.