Mirco D'Incau

Whole Powder Pattern Modelling of cubic metal powders deformed by high energy milling

A Whole Powder Pattern Modelling of the diffraction pattern has been used to study the effect of grinding on some cubic metal powders: crystalline domain size distribution, unit cell parameter average dislocation density, effective outer cut-off radius, effective (screw-edge) dislocation character and faulting probabilities provide a detailed picture of the microstructure of heavily deformed metals. Besides proving the effectiveness of the analytical approach, the present study also suggests some generalization in the behaviour of pure powders of cubic metals subjected to an extensive high-energy milling.

Full Pattern Methods for the Analysis of Plastically Deformed Materials

The recent evolution of powder diffraction line profile analysis toward full pattern methods is discussed. Specific reference is made to the Whole Powder Pattern Modelling (WPPM), as applied to metals and ceramics subjected to strong plastic deformation. Examples concerning three different materials science studies are shown to illustrate features and potentialities of the WPPM approach.

Sub-Surface Residual Stress Gradients: Advances in Laboratory XRD Methods

A new algorithm is proposed to determine the through-thickness residual stress gradient by X-ray Diffraction measurements on progressively thinned components. The procedure is based on a chemical or electrochemical attack of the component surface, which is then measured at each thinning stage. The simple algorithm provided for by a specific norm has been revised to take into account the X-ray absorption effects and the conditions of mechanical equilibrium of the component. The new procedure is illustrated for a typical case of study concerning a shot-peened metal component.

Influence of Shot-Peening Parameters on the Sub-Surface Residual Stress Profiles in Al-7075 Alloy Components

Aluminum alloy (Al-7075-T6) samples were analyzed to determine the in-depth residual stress profile induced by a shot-peening treatment. The influence of coverage degree and Almen intensity on the surface residual stress and on the sub-surface residual stress gradient was investigated. Residual stress profiles were obtained using three different techniques: (i) standard laboratory X-ray diffraction (XRD) residual stress analysis with progressive chemical layer-removal; (ii) XRD residual stress analysis with synchrotron radiation using different X-ray energies, thus changing the penetration depths, and (iii) Blind Hole Drilling (BHD). A comprehensive comparison of the results given by the used techniques is shown.