燃焼合成法による中空パイプ/Al<SUB>3</SUB>Niフォーム複合構造体の作製と気孔性状の解析

Abstract

Al3Ni foam was synthesized by a combustion reaction in a hollow steel pipe. Aluminum powder and nickel powder were blended by Al/Ni molar bending ratio of 4.5, and titanium and boron carbide (B4C) powders were added to increase the heat of reaction. Al3Ni matrix was synthesized by the reaction between Al and Ni, and TiC and TiB2 particles were formed in the Al3Ni matrix by the reaction between Ti and B4C. The blended powder precursor expanded and filled inner space of the pipe during the combustion reaction. The heating rate of the precursor should be lower than a critical level because temperature distribution in the precursor needs to be uniform to avoid inhomogeneous pore formation. At the interface, Al3Ni foam adhered to the steel pipe without cracks or reaction layer formation. The porosity of the foam in the pipe was around 80%, whereas the porosity of the free foamed specimen was 90%. The pore morphology of the free foamed specimen was equiaxed with vertical/horizontal fillet size ratio of 0.95. The pore morphology became elongated shape along the pipe axis, as the inner diameter of the pipe became smaller. The vertical/horizontal fillet size ratio was 1.61 when inner diameter of the pipe and diameter of the precursor were 30 and 25mm, respectively. The pore size became larger when the combustion reaction was carried out in the steel pipe, compared with the free foamed specimen.