The strengthening mechanism and deformation behavior of Mg–Li matrix composite reinforced by Al3La phase formed in-situ through La2O3 particle

Abstract

Here, the low-cost submicron La2O3 particle modified by lithium salts as a precursor was added to Mg–5Li–3Al–2Zn (LAZ532) alloy melt to form in-situ plenty of submicron Al3La phase, finally, the composite with high strength and plasticity reinforced by Al3La phase formed in-situ was obtained. Compared with the LAZ532 matrix alloy, the properties of the composite exhibited significant improvement of UTS~340.1 MPa, TFS~22.4%, UCS~415.5 MPa and CFS~20.3%. The results showed that the Al3La phase formed in-situ not only had a coherent boundary with Mg matrix, but also refined the grains and weakened the {0001} basal texture, which greatly improved the strength and plasticity of the composite. Based on theoretical analysis, the high strength of the composite was mainly attributed to grain refinement, texture strengthening and Orowan strengthening. In addition, according to the slip trace analysis of in-situ EBSD tensile deformation and the results of ex-situ EBSD compression deformation, during the tensile deformation along the extrusion direction (ED), the texture type had no obvious change, and the deformation was dominated by prismatic slip, next pyramidal I <a> slip; during the compressive deformation along the ED, the initial deformation was dominated by basal slip; with the increase of strain, the formation of {1210}<1010> texture was caused by the nucleation of a large number of {1012} extension twins and the rotation of some grains.