Abstract
The mechanical behaviour of MgAl alloys can be largely improved by the formation of an intermetallic Laves phase skeleton, in particular the creep strength. Recent nanomechanical studies revealed plasticity by dislocation glide in the (Mg,Al)2Ca Laves phase, even at room temperature. As strengthening skeleton, this phase remains, however, brittle at low temperature. In this work, we present experimental evidence of slip transfer from the Mg matrix to the (Mg,Al)2Ca skeleton at room temperature and explore associated mechanisms by means of atomistic simulations. We identify two possible mechanisms for transferring Mg basal slip into Laves phases depending on the crystallographic orientation: a direct and an indirect slip transfer triggered by full and partial dislocations, respectively. Our experimental and numerical observations also highlight the importance of interfacial sliding that can prevent the transfer of the plasticity from one phase to the other.
Highlights
The mechanical response of composite materials is dependent on the properties of their different phases individually, and largely on the properties of their interfaces
It can be seen in the figure that the microstructure consists of two phases, i.e. α-matrix reinforced with an intermetallic Laves phase skeleton
The critical resolved shear stress (CRSS) values for the Mg phase are much lower than the CRSS values reported for the same slip systems in the C14 Mg2Ca Laves phase, which were determined as ≈520 MPa, ≈440 MPa and ≈530 MPa by micropillar compression [2] (NB: a direct comparison is impeded by the brittleness of the Laves phase and the size effect encountered in microcompression testing of Mg, resulting in a CRSS for basal slip of the order of ≈ 7 MPa as opposed to 0.52 MPa [17] measured macroscopically [20])
Summary
The mechanical response of composite materials is dependent on the properties of their different phases individually, and largely on the properties of their interfaces. Lightweight Mg-based composites with a controlled proportion of Al and Ca can be strengthened by the precipitation of a Laves phases skeleton [1]. The reinforcement potential of Laves phases in these alloys is primarily due to their high strength compared to the matrix phase [2]. Laves phases are hard intermetallic phases with a topologically close packed structure arranged in a cubic (C15) or hexagonal (C14 and C36) unit cell [3,4]. The mechanical response of such a dual phase microstructure typically shows plasticity in the Mg matrix and fracture in the hard-intermetallic phase [1,5]. While effectively strengthening the composite, the brittleness of the Laves phase limits the maximum strength and the formability of the composite
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
