Abstract The adhesion strength as well as the crack resistance of hard CVD coatings on cutting tools are widely influenced by the appertaining residual stress states. They are generated during cooling down from coating temperature, or during a subsequent heat treatment. To enhance the knowledge of the residual stress development in such CVD coatings on steels, X-ray residual stress analyses were performed during the cooling process. Therefore, a high temperature chamber for a Ψ-diffractometer was developed and manufactured. It allows X-ray residual stress analyses at temperatures of up to at least 1000°C using a measuring range of 2θ ≥ 94° at |Ψ| ≤ 60°.

A series of measurements has been performed on the neutron strain scanner of the Laboratoire Leon Brillouin in order to explore the limits of the spatial resolution achievable by neutron stress analysis. Two types of samples were investigated, i.e. sandwich structures consisting of thin sheets of copper and aluminum nitride (AIN) and shot peened steel sheets. With slits before and after the sample as small as 0.3 × 10 mm2 (AIN) or even 0.15 × 10mm2 (steel) counting times were not longer than 1–2 h/peak. Checks revealed that a spatial resolution of ≈0.3 mm (AIN) resp. 0.15 mm (steel) was indeed achieved in the direction perpendicular to the surface. Using partial immersion of the gauge volume, near-surface/interface strains could be explored with even higher spatial resolution, down to ≈30 μm in the case of steel. The stress gradients determined by neutron diffraction were checked by measurements using other techniques.

Thin plates of AIN were joined with Cu sheets by active brazing, and the residual stresses generated by the brazing process were investigated by neutron and X-ray diffraction. Residual stresses with values between 100 MPa and - 150 MPa were found in the ceramic layers. The residual stresses in the Cu layers had to be inferred from the balance of forces, because coarse grain effects and a strong variation of the stress-free lattice constant across the thickness due to interdiffusion of the brazing metal and the Cu layer did not allow to obtain reliable residual stress values by diffraction methods. The results are discussed with regard to failure of the joints due to cracking.

La repartition des textures sur l'epaisseur de l'echantillon dans du fer « armco » lamine a froid ete examine par diffraction des rayons X. Contrairement a la litterature, l'echantillon en fer armco d'un taux de laminage a froid final d'environ 67% analyse ici presente une repartition complexe des textures a travers la section Dans le domaine proche de la surface se trouve une texture typique des materiaux cubiques-centres lamines a froid, caracterisee par une composante {001} etalee de ±60° autour de l'axe Dans les domaines inferieurs, soumis a un cisaillement modere, on trouve une texture de Goss essentiellement caracterisee par des orientations cristallographiques autour de {110} . Elle a son maximum d'intensite a environ 25% de l'epaisseur de l'echantillon Au coeur de l'echantillon, ou le cisaillement disparait pour des raisons de symetrie, une texture fibreuse avec l'axe de la fibre perpendiculaire a la surface de l'echantillon domine, accompagnee d'une composante de texture de laminage de type {001} comme en surface. Les transitions entre les differentes composantes sont progressives.

The depth distribution of the crystallographic texture of a cold rolled low carbon steel was investigated using X-ray diffraction. In contrary to literature, the material under investigation showed a complex distribution of the texture with depth. At and near the surface a typical rolling texture {001}<110> with a spread of about +/-60 degrees around the <110> axis was found. In deeper regions, the rolling texture was followed by a Goss texture {110}<001> with a maximum at 25% of the thickness below the surface. In the sample centre, however, a <111> fibre texture with the fibre axis in normal direction and a small amount of a {001}<110> rolling texture were observed. Between these texture components smooth transitions occur.

Grinding residual stress states in Al2O3 and AlN were investigated by means of X-ray diffraction using a conventional Bragg-Brentano geometry as well as an advanced quasi-parallel beam set-up. Depending on the grinding conditions, steep near-surface residual stress gradients were found and discussed with respect to the grinding process. Furthermore, it could be proved, that residual stress analyses performed in quasi-focussing Bragg-Brentano geometry cannot resolve residual stress maxima or huge changes of the residual stress state near the surface [1]. In contrary, X-ray residual stress analyses using a quasi-parallel beam allow a highly resolved determination even of steep graded grinding residual stress states.

Due to the individual steps of manufacturing, various kinds of residual stresses and strains are induced in devices and components of microsystems. These residual stress states often differ considerably from those determined in well-known conventional materials and material compounds. This is caused by the small dimensions of the single components and by the great variety of material combinations used. X-Ray diffraction is a powerful tool also for the investigation of the residual stress states in microsystems, because it enables the non-destructive testing of materials and components, and the investigation of very small measurement volumes. Due to the small thickness of the individual layers in multi-layered microsystems, the X-rays penetrate in many cases deeply into the samples, and diffraction patterns occur in layers of different materials. Using new X-ray optics like fibres and mirrors, the size of the spots to be measured can be reduced to very small lateral dimensions without unacceptable loss of intensity. As a result of this miniaturisation, the material within the volume to be measured differs more and more from the polycrystalline state. In this situation, new detection systems like area detectors can be used successfully. New evaluation procedures are required.

AlN is of increasing importance as structural material in microelectronics and microsystems in order to replace Al2O3. However, the knowledge of mechanical properties of this material is still restricted, and an enhanced understanding about the material behaviour of AlN requires the knowledge concerning the residual stresses. In order to determine the residual stresses by means of X-ray diffraction, X-ray elastic constants are needed which account for the elastic anisotropy and the coupling conditions of the crystallites in the polycrystalline material. Therefore, the X-ray elastic constants of AlN were determined for selected lattice planes {hkl} by X-ray diffraction. From the single crystal elastic constants calculated on the base of this knowledge, the X-ray elastic constants were derived for all sets of lattice planes {hkl} of interest. Employing these data, X-ray residual stress analyses were performed on differently machined samples of AlN.