Strengthening mechanism of porous Cu-Al-Mn alloy via nanoscale Al2O3 introduced in-situ through staged powder metallurgy process

Currently, the simultaneous enhancement of mechanical strength and ductility in porous composite alloys remains a formidable challenge. To address this limitation, we have innovatively synthesized in-situ nanoscale amorphous Al₂O₃ in porous composite Cu-Al-Mn (CAM) alloys utilizing a well-orchestrated staged powder metallurgy (PM) process, employing Cu, Mn, and oxygen-containing Al elemental powder as raw materials. In the optimized porous CAM/Al₂O₃ processed by staged PM, strong equiaxed crystals in average grain size 29.20 μm with a near-unity aspect ratio, and the pore soft phase characterized by pore sizes ranging from 0.1 to 10 μm and its porosity of 33.20 % was found. Crucially, in-situ formation of amorphous Al₂O₃ nanoparticles strategically positions themselves along grain boundaries and pore edges, constructing a protective shell structure that safeguards grains against fracture under severe compressive deformation. This protective architecture, coupled with the abundant soft phase providing ample deformation accommodation, facilitates an exceptional balance of strength and ductility. Consequently, a remarkable enhancement in ultimate compressive strength (∼ 570.6 MPa) by 1.8 times is achieved, while maintaining a ductility capability (∼ 44.3 %) 3.0 times that of comparable porosity porous CAM alloy. The staged PM process for fabricating porous Cu-Al-Mn alloys with high strength and ductility via utilizing partially oxidized Al powder as one of the raw materials without relying on the difficult-to-obtain microstructure required in high strength structural materials. This approach demonstrates the capability of staged PM process in fabricating high performance porous Cu-Al-Mn alloys with controllable structures.