Interfacial bonding, texture evolution, and mechanical properties of different structured extruded Mg-7Gd-4Y-1Zn-0.2Zr and Mg-3Zn-1Al-1Ca-0.5Mn composites

In the present study, different structured, Mg-7Gd-4Y-1Zn-0.2Zr (GWZ) and Mg-3Zn-1Al-1Ca-0.5Mn (ZA) alloys based bi-metal composites were fabricated through extrusion. In particular, we reported that the strong and large diffusional interfacial thickness comprised of fine grains along with the segregation of the different elements at the interfacial region transferred the load to the base of the composite, and hence acted like a bonder and increased the stability of the interfaces. Most specifically, the rare “composite texture” having c-axes//radial direction (RD) and tilted c-axes//extruded direction (ED) with very low texture intensities was developed in all composites, which is the key requirement for retaining high strength and high ductility. The microstructure of GWZ Mg alloy consists of dense lamellar LPSO_s, blocky LPSO_s, rod-shaped LPSO_s, Mg-enriched rare earth (RE) precipitates, and broken square-shaped RE-enriched precipitates. In contrast, the microstructure of ZA Mg alloy is comprised of MgAl₂Ca laves, different-shaped Al₈Mn₅, and nano-sized Mg₁₇Al₁₂ precipitates. Particularly, after extrusion, the strongly bonded interfacial region was decorated by Al, Ca, Gd, Y, and Zr elements. The WAW bi-metal composite showed a wavy interfacial morphology compared to the AWA and AW bi-metal composites and the diffusional thickness for all composites was quite large (> 20 µm). Therefore, based on the above brief discussion, the AWA bi-metal composite (having HAGBs > 93%), exhibited exceptionally high performance. The elongation to fracture and strength under compression was significantly higher (EF ∼ 50%, UCS ∼ 17.70%) compared to the GWZ Mg alloy. Likewise, the bendability of the AWA bi-metal composite was much higher (∼ 103.2%) than the GWZ Mg alloy and higher than other composites. Therefore, the fabrication of bi-metal composites is a practical approach in achieving strength and ductility.