Use of finite element modeling to interpret diffraction peak broadening from elastic strain distributions

An approach employing the finite element (FE) method to interpret diffraction peak broadening due to elastic strain distributions is presented that provides a model of the local variations of elastic strain and stress in a composite or multiphase microstructure. The method involves averaging elastic strain output from a representative FE model to generate a strain distribution analogous to the averaging taking place in the diffraction process. The procedure assumes that the FE model adequately represents the thermally stressed system, an aspect addressed by comparison of the strain distributions obtained from diffraction data and the FE model. Example applications are presented for thermal residual strain in 11 and 60vol.%WC-Ni composites. The stress in the WC, which is compressive on average, becomes tensile at corners and at locations that are normal to WC-Ni interfaces. The Ni stress, which is tensile on average, is compressive in narrow bands between WC particles. In addition, asymmetry of the Ni distribution on the high strain side, due to localized plastic flow, is successfully modeled for the 60vol.%WC-Ni. Composition effects are also represented. Uniqueness aspects and limitations of the procedure are discussed.