Structural characterization of copper alloy foams prepared by powder metallurgy

M.T. MALACHEVSKY; E. ZELAYA; M. ESQUIVEL; E.OLIBER; C.D'OVIDIO

Bariloche

Simposio; SLAFES XXIII; 2018

Cellular materials are currently being used for applications involving en-ergy absorption by irreversible plastic deformation. The possibility of em-ploying materials presenting pseudoeslastic behavior would expand their ap-plication to dynamic solicitation with reversible deformation. Copper shapememory alloys in the Cu-Al-Ni and Cu-Zn-Al systems had being largelystudied along the years [1]. In particular, cellular materials had alreadybeing prepared using space holders inltrated with melted Cu-Zn-Al alloys[2]. Nevertheless their resulting grain size is in the millimetre range, leadingto transgranular fracture after a few compression cycles. The powder met-allurgy route is proposed as an option for grain size reduction in an eort toavoid this failure. Cu-Ni-Al system was selected as it is more promising foractuator applications. The initial alloy powder precursor was prepared in aFristsch Pulverissette 7 mill, to obtain a pre-alloyed mixture of Cu-13.5Al-4Ni composition. This powder is manually mixed with the space holder(ammonium bicarbonate) that is eliminated after compaction with a ther-mal treatment. Then the pellet is encapsulated in argon and sintered for 2days before quenching in water to retain the shape memory phase. Phaseformation is controlled by x-ray diraction. X-ray tomography (X-RadiaMicro XCT-200) allows a complete structural characterization of the ob-tained foams. The cell size distribution, connectivity and resulting porositycan be evaluated from the volumetric reconstruction. Tortuosity is obtainedfrom spatial distance maps and cell wall thickness is evaluated from voxelintensity variation.