Deformation of Mg-γMg17Al12 in situ composites: Room temperature mechanical behaviour, microstructures and mechanisms

Abstract

Deformation tests at room temperature have been carried out on a series of in situ Mg-Mg17Al12 composites with volume fraction of Mg17Al12 phase varying between 20 % and 60%. Regardless of the phase volume fraction, these Mg-Mg17Al12 composites that are prepared by solidification consist in magnesium-rich dendrites and a eutectic mixture. The eutectic mixture is made of magnesium fibres embedded in a matrix formed by the Mg17Al12 phase, a hard and brittle complex metallic alloy. Compression tests at room temperature have shown that a global plastic deformation is observed even though the soft phase is always enclosed in the brittle one. According to the strain-stress curve, deformation proceeds in two stages: a first stage at low stress (~ 100 MPa) and low strain ( < 0.01) almost similar for all the composites and a second stage characterized by a strain hardening effect along with a significant deformation for composites with  phase volume fraction smaller than 40 %, whereas no or little additional deformation is observed for composites with volume fraction higher than 40% that break at high stress (~ 400 MPa). Microstructural observations of the deformed samples have evidenced dislocations in the Mg17Al12 matrix and their localisation as pile-ups and slip bands as well as the transmission of deformation across the eutectic mixture. The plasticity of the Mg17Al12 phase and the mechanical behaviour of the Mg-Mg17Al12 composites are discussed with respect to the microstructure characteristics and to the specific atomic features of complex metallic alloy phases.

Microstructure, Mechanical, and Corrosion Behavior of Al2O3 Reinforced Mg2Zn Matrix Magnesium Composites

“…First, it must be biocompatible and have good corrosion resistance. Secondly, the mechanical strength of the reinforcement should be better than the matrix of the composite [13,30,[34][35][36]. It is possible to say that ceramic reinforcement elements such as Al 2 O 3 , SiC, and HA (hydroxyapatite) can meet these requirements [9,13,37,38].…”