*Article* **Incipient Bulk Polycrystal Plasticity Observed by Synchrotron In-Situ Topotomography**

#### **Henry Proudhon 1,\*, Nicolas Guéninchault 1,†, Samuel Forest 1 and Wolfgang Ludwig 2,3**


Received: 10 September 2018; Accepted: 10 October 2018; Published: 18 October 2018

**Abstract:** In this paper, we present a comprehensive 4D study of the early stage of plastic deformation in a polycrystalline binary AlLi alloy. The entire microstructure is mapped with X-ray diffraction contrast tomography, and a set of bulk grains is further studied via X-ray topotomography during mechanical loading. The observed contrast is analyzed with respect to the slip system activation, and the evolution of the orientation spread is measured as a function of applied strain. The experimental observations are augmented by the mechanical response predicted by crystal plasticity finite element simulations to analyze the onset of plasticity in detail. Simulation results show a general agreemen<sup>t</sup> of the individual slip system activation during loading and that comparison with experiments at the length scale of the grains may be used to fine tune the constitutive model parameters.

**Dataset:** 10.5281/zenodo.1412401

**Keywords:** polycrystal plasticity; X-ray diffraction imaging; topotomography; in situ experiment; finite element simulation; lattice curvature; rocking curve
