Asymmetry in the Mechanical Properties of Block Ni-Cr-Al Superalloy Foam Fabricated by the Combination of Powder Alloying and Hot Rolling Processes

초록

A block Ni-Cr-Al superalloy foam with dimensions of 300 mm (width direction, WD) x 500 mm (rolling direction, RD) x 60 mm (normal direction, ND) was fabricated using powder alloying, multi-sheet stacking, and hot rolling processes. The structural characteristics, microstructure, and mechanical asymmetry of the block Ni-based foam were investigated. Analysis of the structural features showed that the interfaces between the sheets had complex strut interactions, such as contacted (deformed) and intersected struts. The average pore size along the directions was measured to be 2569.6 mu m (WD), 2988.1 mu m (RD), and 2493.2 mu m (ND). The average thickness of the strut was 340.8 mu m, and the wall thickness of the strut was 27.7 mu m. The elemental distributions in the struts were uniformly controlled, and the block foam consisted of gamma (matrix) and gamma' (Ni3Al) phases. Tensile properties in the ND direction showed a yield strength of 0.175 MPa, tensile strength of 0.233 MPa, and elongation of 2.54%, while the tensile properties in the RD direction were 1.27 MPa (YS), 3.01 MPa (UTS), 8.92% (El.) respectively. The foam was observed to have a compressive yield strength of 0.795 MPa in the ND direction, and that of 2.18 MPa in the RD direction were obtained. The asymmetry and anisotropy of these mechanical properties could be explained by the difference in pore sizes along the direction, and the structural characteristics of the sheet interface generated by sheet stacking and rolling.

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