Contribution of robust transitional interface featuring Mg segregation to the strength-ductility synergy of boron nitride nanosheets/Al composite

Interfaces play a key role in affecting the strengthening efficiency of metal matrix composites. Herein, boron nitride nanosheets (BNNSs)-AlN-Al transition interface featuring Mg segregation was designed, which contributes to the exceptional strengthening of BNNSs/Al-4Mg composite. Both experiments and theoretical calculations show that Mg solutes tend to segregate at the BNNS/Al interface. Such Mg segregation is revealed to enhance interface bonding and cohesion, which increases the load-transfer efficiency and hence contributes to the exceptional strength of composites. The transitional interface featuring AlN transitional nanolayer and Mg segregation is supposed to alleviate the stress concentration near the interface by mitigating the deformation incompatibility between BNNSs and Al matrix. It is considered that Mg segregation facilitates planar slip of dislocations which benefits strain/stress transfer and delocalization at the interface. Furthermore, the fracture morphologies suggest the BNNSs-AlN-Al transition interface can effectively blunt crack propagation and change crack propagation path, which notably contributes to the exceptional strength-ductility of BNNSs/Al-4Mg composite. The present work provides a new solution to design aluminum matrix composites with excellent mechanical properties through interfacial engineering.