Anisotropic ductile fracture: Part II: theory

AlSi10Mg cylinders produced by laser powder-bed fusion have somewhat different yield behavior for cylinders with XY orientation and Z orientation. Earlier yielding for Z-oriented samples is likely related to micro-residual stress, resulting from the difference in thermal expansion of the aluminum matrix and cellular silicon. Smaller tensile reduction in area of Z-oriented samples is related to tearing along the softer region at the boundaries of melt pools, where the silicon cell spacing is larger. Indentation measurements confirmed the lower hardness at the edges of melt pools.

Anisotropic Mechanical Behavior of AlSi10Mg Parts Produced by Selective Laser Melting

Sources of anisotropy in metals are discusssed as well as ways of interpreting and modelling this behaviour. A number of case studies are presented relating to mechanical and magnetic properties.

https://www.tandfonline.com/doi/pdf/10.1179/1743284715Y.0000000118

Critical Assessment 16: Anisotropy in metals

Results obtained from mechanical tests on a Ti6%Al4%V sheet alloy were used to obtain the biaxial normal stress and the in-plane simple shear flow stress sections of its yield locus The critical resolved shear stress (CRSS) of the different activated slip systems is derived from these experimental results of mechanical tests combined with microstructural observations A strong asymmetry of the CRSS and some influence on it of the hydrostatic stress state was found for pyramidal 〈 c + a 〉 systems, ie a deviation from the Schmid law Owing to the high sharpness of the texture in this alloy, a quasi-single-crystal approximation of the plastic anisotropy on the rolling plane (RP) and of the yield locus sections measured was made The good agreement between the simulated and the experimental results encourages the use of the proposed CRSS values for a simulation of polycrystalline texture development and yield locus derivation

Two-dimensional sections of the yield locus of a Ti6%Al4%V alloy with a strong transverse-type crystallographic α-texture

An alpha + beta Ti-6Al-2Nb-lTa-0.8Mo alloy with an initial Widmanstatten structure was thermally treated to produce a wide range of microstructures. The effects of individual microstructural parameters on deformation behavior and mechanical properties were investigated. The results show that the Widmanstatten colony boundaries are major barriers to slip. However, the slip distance can be decreased to a distance equal to the thickness of acicular alpha by transforming the beta phase in the Widmanstatten structure to martensite by quenching from 950°C. The decrease in slip distance is accompanied by a 25 pct increase in yield strength with no loss in ductility. A large decrease in ductility occurs after excursions above the beta-transus. The development of both equiaxed beta grains during heating in the beta phase field and continuous grain boundary alpha during cooling in the alpha + beta phase field leads to strain localization along prior beta grain boundaries.

The effect of microstructure on the deformation modes and mechanical properties of Ti-6Al-2Nb-1Ta-0.8Mo: Part I. Widmanstätten structures

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 proper...

P. J. E. Forsyth

Papers

Directionality in structure-property relationships: aluminium and titanium alloys