Correlation of polarized light phenomena with the orientation of some metal crystals

Abstract

A photometric study was made of t h e refl ection of plane pol ari zed li ght no rmalh' incident in a metallographic microscope upon specim ens of tin, aluminum, and monel with variou s surface treatments. A high degree of correlation was found in most c9,se~ between the extin ction position and the projection of the optic axis or of the cubic axis making the greatest angle with the surface normal. Moreo ver, a fourth power sine relationship was obser ved between the change of intensity and t he angle between t.he s urface normal and the optic ax is in t in. The inte nsity correlation in the case of the cubic metals was not so clear, but a sli ght indication of position d epend ence was obse rv ed for a luminum . The res ults indicate that the optically anisotropic effects obser ved with cubic m etals can be caused both by an isotropic fi lm s a nd by oriented surface conto urs, but that the latte r is the source of t hose effects that are correlated \\'i t h t he crystall ograph ic ori e ntation of t he grain.

Epitaxial NaxCoO2 Thin Films via Molecular-Beam Epitaxy and Topotactic Transformation: A Model System for Sodium Intercalation

“…The optical microscope image taken with a polarizer and analyzer set at an angle of approximately 0° from one another shows domains visible in AFM images. Polarized light microscopy can distinguish grain orientation in polycrystalline materials. , The contrast seen in this method is perhaps due to different crystallographic facets being exposed and creating anisotropic roughness, which reflects polarized light depending on orientation. Optical microscopy reveals a large variation in domain sizes.…”

Quantitative polarised light microscopy of metals

“…Anodised aluminium alloys become optically anisotropic under polarised light microscopy due to the light interaction between the oxidised film on the grain surface. The light reflection from the anodised surface and the interface between the anodic layer and Al substrate intertwined with scattering and absorption within the anodic layer generates a specific optical appearance as has been previously described (16,26,124).…”

“…The alloy studied is a commercially available 2XXX aluminium alloy. It has long been the case that this alloy group can be anodised to generate qualitative optical orientation contrast (26). Franklin and Stirland discovered in 1963 that this optical anisotropy is due to variations in pore inclination as the formed Alumina on the surface is in different crystals.…”

“…In this case properties vary along with their crystal structure. The textured or directionally microstructure typically causes during the forming process (1,3,5,(26)(27)(28)(29). Also grain size has a measurable effect on most mechanical properties.…”