Structural characterization of copper alloy foams prepared by powder metallurgy

M.T.MALACHEVSKY; E. ZELAYA; E.OLIBER; M.R. ESQUIVEL; C.DOVIDIO

Bariloche, Rio Negro, Argentina

Congreso; XXIII Latin American Symposium on Solid State Physics; 2018

Universidad de Rio Negro-Comisión Nacional de Energía Atomica

Cellular materials are currently being used for applicationsinvolving energy absorption by irreversibleplastic deformation. The possibility of employing materialspresenting pseudoeslastic behavior would expandtheir application to dynamic solicitation withreversible deformation. Copper shape memory alloysin the Cu-Al-Ni and Cu-Zn-Al systems had being largelystudied along the years [1]. In particular, cellularmaterials had already being prepared using spaceholders inltrated with melted Cu-Zn-Al alloys [2].Nevertheless their resulting grain size is in the millimetrerange, leading to transgranular fracture after afew compression cycles. The powder metallurgy routeis proposed as an option for grain size reduction in aneort to avoid this failure. Cu-Ni-Al system was selectedas it is more promising for actuator applications.The initial alloy powder precursor was prepared in aFristsch Pulverissette 7 mill, to obtain a pre-alloyedmixture of Cu-13.5Al-4Ni composition. This powderis manually mixed with the space holder (ammoniumbicarbonate) that is eliminated after compaction witha thermal treatment. Then the pellet is encapsulatedin argon and sintered for 2 days before quenching inwater to retain the shape memory phase. Phase formationis controlled by x-ray diraction. X-ray tomo-graphy (X-Radia Micro XCT-200) allows a completestructural characterization of the obtained foams.The cell size distribution, connectivity and resultingporosity can be evaluated from the volumetric reconstruction.Tortuosity is obtained from spatial distancemaps and cell wall thickness is evaluated from voxelintensity variation.