H. Xiong; M. Yu; L. Gu; J. Wang; L. Zhou; J. Wang; J. Llorca; X. Zeng
Acta Materialia 301 (2025) 121532
The specific stiffness of structural metallic alloys is around 26 MJ⋅kg−1 and conventional strengthening strategies
(alloying and thermomechanical processing) cannot overcome this limitation. It is, however, well established
that superior values of specific stiffness can be achieved by reinforcing with stiff ceramic particles. Mg alloys are
ideal candidates for this purpose because of their moderate mechanical properties and low density, but the
introduction of large volume fractions of ceramic particles always systematically led to the composites with
negligible ductility due to the weak particle/matrix interfacial bonding and poor toughness of the interface
region. Here, we report a novel Mg-5Zn-0.2Ca/SiC composite with superior specific stiffness (34 MJ⋅kg−1), high
strength (> 300 MPa) and ductility (> 7 %). The composite is manufactured through semi-solid stirring, followed
by extrusion, a technique can be easily scaled-up for industrial applications. The co-segregation of Zn/Ca atoms
along the interface enhances the atomic bonding and delays interface decohesion and microcrack initiation at the
particle/matrix interface. Moreover, the activation of 〈c + a〉 dislocations near the Mg alloy/SiC interface was
confirmed, and their subsequent rearrangement into dislocation arrays was found to promote dynamic recrys
tallization, thus contributing to crack-tip blunting and enhanced damage tolerance. This mechanism improves
the toughness and delays crack propagation, allowing the development of strain hardening and improving
dramatically the tensile ductility of the composite. The present work provides an efficient approach to improve
the interfacial properties and further inspires the development of high-performance metal matrix composites
with exceptionally high modulus, strength and ductility.