Liquid metal embrittlement (LME) is a phenomenon that can appear in solid metal or alloys that undergo deformation while in contact with a liquid metal or alloy [1, 2]. The apparition of this embrittlement depends on several factors such as the physicochemical properties of the materials in contact and the mechanical stresses applied to the solid. There are several proposed mechanisms to explain LME; all of them rely on micro and atom-scale phenomena [1, 2]. Direct observations at these scales would give more information about the mechanisms involved. The goal of our study is to carry out in-situ mechanical tests to observe the effect of a liquid alloy on the micromechanical behaviour of a solid alloy. The liquid alloy chosen for this study is the eutectic Ga-In (eGaIn), which has a melting point of 16°C. The solid alloy chosen is the Cu-30%Zn alpha brass. A preliminary study shows that the Cu-30%Zn brass can present LME by the eGaIn [3]. We designed a clamped beam bending test for a notched brass specimen. We carry out this experiment in a HELIOS 660, the ion source was used to machine the sample and the electronic source was used to take images before, during, and after the test. A micromanipulator was used to place a drop of liquid eGaIn inside the notch. However, to prevent the formation of the intermetallic CuGa2 that could consume the entire liquid alloy before the start of the test, a W nanometric layer was deposed in the notch before posing the eGaIn. This W layer would break during the test; hence, there is contact between the solid and the liquid only during the deformation of the solid. To account for the effects of the misorientation between grains, EBSD characterisation was done on the sample before the test. The observations done during this experiment provided new evidence of the mechanisms involved in the micromechanical behaviour of 30%Zn brass in contact with the eGaIn. This work was done with the support of the French National Research Agency (ANR) under the project ANR GauguIn (N° ANR-18-CE08-0009-01). References [1]Popovich, V. V. and Dmukhovskaya, I. G., “The embrittlement of metals and alloys being deformed in contact with low-melting alloys (a review of foreign literature)”, Sov. Mater. Sci., vol. 23, no. 6, pp. 535–544, 1988. [2]Norkett, J. E., Dickey, M. D., and Miller, V. M., “A Review of Liquid Metal Embrittlement: Cracking Open the Disparate Mechanisms”, Metall. Mater. Trans. A, vol. 52, no. 6, pp. 2158–2172, Jun. 2021. [3] Ezequiel, M., Proriol Serre, I., “Effect of the Small Punch Test sample geometry on the Liquid Metal Embrittlement of Cu-30 wt% Zn by the eGaIn”, MATEC Web Conf., vol. 340, Nov 2021.