Duplex stainless steel is an example of composite material with approximately equal amounts of austenite and ferrite phases. Difference of physical and mechanical properties of component is additional factor that contributes appearance of residual stresses after welding of duplex steel plates. Measurements of stress distributions in weld region were made by X-ray diffraction method both in ferrite and austenite phases. Duplex Steel plates were joined by GTAW (Gas Tungsten Arc Welding) technology. There were studied longitudinal and transverse stress components in welded butt joint, in heat affected zone (HAZ) and in points of base metal 10 mm from the weld. Residual stresses measured in duplex steel plates jointed by welding are caused by temperature gradients between weld zone and base metal and by difference of thermal expansion coefficients of ferrite and austenite phases. Proposed analytical model allows evaluating of residual stress distribution over the cross section in the weld region.
A theoretical model has been developed to explain the variation of surface residual stress introduced by shot-peening with external plastic deformation, during a uniaxial tensile test. The model is based on the difference of yield stress values of the shot-peened surface layer and the remaining bulk material. It has been shown that the model fits well with experimental results obtained for the base metal and heat-affected zone of a 5.0Cr-0.5Mo steel.
É conhecido da teoria da difração de raios X que os alargamentos das linhas de reflexões de uma amostra de pó estão associados com as imperfeições dos cristalitos, com os erros instrumentais e com efeitos da radiação utilizada. Nesse estudo, são separados os parâmetros microestruturais de duas amostras beneficiadas de caulinitas provenientes de depósitos brasileiros de diferentes regiões, usando o método de ajuste do perfil "Profile Matching", também conhecido como ajuste Le Bail, incorporado ao programa FullProf, que trata de difratogramas de raios X pelo método de Rietveld. O refinamento de Rietveld foi realizado com os dados de um material padrão LaB6, para obter os parâmetros da função instrumental e como uma forma de validar o método "profile matching". Uma função pseudo-Voigt modificada (TCHZ) foi usada para o ajuste dos perfis. Os valores das larguras integrais betah e dos parâmetros etah calculados pelo programa serviram de dados para a aplicação do "modelo" aqui denominado TCHZpV. Os resultados dos parâmetros microestruturais calculados pelos dois procedimentos foram, então, comparados com boa concordância, indicando que os tamanhos dos cristalitos constituem a maior fonte das imperfeições cristalinas das amostras de caulinita.
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