Synchrotron 3D X-ray Laue microdiffraction, available at beamline 34-ID-E at Advanced Photon Source in Argonne National Laboratory, is a powerful tool for 3D non-destructive mapping of local orientations and strains at sub-micron scale in the bulk. With this technique, it is possible to study local residual stresses developed during manufacturing or while in service due to interactions between, for example, different phases and/or grains with different orientations in materials containing multiple or single phase(s). Such information is essential for understanding mechanical properties and designing advanced materials, but is largely non-existent in the current generation of materials models. In the present paper, the principle and experimental set-up of the 3D microdiffraction are introduced, followed by a description of a method for quantification of the local plastic deformation based on high-angular-resolution orientation maps. The quantification of local residual stresses in two model materials, ductile cast iron (two phases) and partially recrystallized pure nickel (single phase), using 3D microdiffraction will then be presented. The results show that 3D microdiffraction is important for understanding the origin of local residual stresses and to relate them to the microstructural evolution. Finally, the limitations of the 3D microdiffraction on the current generation synchrotron source and new possibilities after the synchrotron upgrade are discussed.

An inverse magnetocaloric effect is studied in Ni${}_2$ Mn${}_{1+x}{X}_{1-x}$ -type Heusler alloys. Principally known for their shape-memory properties, these alloys also exhibit significant entropy and temperature changes ($\mathrm{\Delta }S$ and $\mathrm{\Delta }{T}_{Ad}$ , respectively) under adiabatic conditions when a modest magnetic field is applied. We investigated the impact on magnetocaloric properties of introducing substantial chemical disorder on the $X$ -site ($X=\mathrm{Si},\mathrm{Ga},\mathrm{In}$ ), of replacing Ni with nonmagnetic Ag, and of replacing a small amount of Mn with Gd. While a reduction in $\mathrm{\Delta }S$ is observed in the first two cases, we observe a significant enhancement of $\mathrm{\Delta }S$ when a small amount of Gd is substituted for Mn. A thermodynamic analysis was conducted using magnetization and heat capacity data to estimate adiabatic temperature changes in the range of $\mathrm{\Delta }{T}_{Ad}\simeq$ $-1$ to $-3$ K for a 5 T magnetic field. Several alloys characterized in this study exhibit these respectable $\mathrm{\Delta }{T}_{Ad}$ values near room temperature, making them potentially viable candidates for magnetic refrigeration applications.

Spatially resolved elastic strains in the bulk interior of a laminated Ti-Al metal composite were studied during in situ tensile loading at strains up to 1.66% by a synchrotron-based micro-diffraction technique, namely differential aperture X-ray microscopy (DAXM). For both Al and Ti grains, deviatoric elastic strains were estimated based on polychromatic X-ray microbeam diffraction, while lattice strains along the normal direction of the tensile sample were directly measured using monochromatic X-ray microbeam diffraction. The estimated deviatoric strains show large spatial variations, and the mean values are consistent with the external loading conditions, i.e., increasing tensile strain along the tensile direction and increasing compressive strain along the sample normal with increasing loading. The directly measured lattice strains also show large spatial variations, although the magnitude of this variation is smaller than that for the estimated deviatoric strain. The directly measured lattice strains in Ti grains are largely consistent with the external loading, whereas those in Al grains are in contradiction with the external loading. The causes of the experimental results are discussed and related to both the laminated microstructure of the composite material and the limitations of the techniques.