No abstract

Specimens of pure Fe and of Fe-0.8 mass % C, Fe-0.5 mass % Cr, Fe-4.0 mass % Cr, Fe-4.0 mass% Ni, and Fe-10.0 mass% Ni alloys were borided in boriding powder. A boron-compound layer developed consisting of a surface-adjacent “FeB” sublayer on top of an “Fe2B” sublayer. Layer-growth kinetics were analyzed by measuring the extent of penetration of the “FeB” and “Fe2B” sublayers as a function of boriding time and temperature in the range 1025–1275 K. Layer growth is dominated by B diffusion through “FeB/Fe2B”. This diffusion process is of strongly anisotropic nature. Consequently, ragged interfaces occur between the substrate and the boride layers. The depths of the tips of the most deeply penetrated “FeB” and “Fe2B” needles have been taken as measures for diffusion in the easy [001] diffusion directions. Assuming unidirectional B diffusion and parabolic growth, a simple model of layer growth has been given. It accounts for the specific volume difference between “FeB” and “Fe2B”. In contrast with earlier work, the model provides values for the kinetic parameters for growth of each of the phases in the boron-compound layer.

No abstract

No abstract

No abstract

No abstract

A quantitative formulation is given of the X-ray diffraction determination of (elastic) lattice deformation in a direction determined by two angles ff and q~ with respect to the specimen frame: the so-called sin2ff method giving full credit now to crystallographic texture. In most cases of practical X-ray stress analysis, (residual) stresses are evaluated by the traditional sin2~, method using quasi-isotropic X-ray elastic constants depending on the lattice plane {hkl} chosen for the measurement but not on the directions q~ and ft. For the case of a textured specimen, however, the single-crystal elastic bitensor components should be coupled to the orientation distribution function (o.d.f.). At variance with most papers published on this subject, which describe the texture using ideal texture components, a general method is developed making full use of relevant o.d.f, theory. It is demonstrated that for orthorhombic specimen symmetry no ff splitting occurs in contrast with the case of monoclinic specimen symmetry. The theory developed is used to explain some experimental results published previously. All calculations use Reuss's theory of elasticity which neglects the mutual coupling of the crystallites.

No abstract