Al-Ni intermetallic foam is fabricated by a combustion reaction. Al and Ni powders are blended together with Ti and B_4C powders (reactive foaming agents). The blended powder is extruded to make a long rod precursor. When one end of the rod precursor is heated and the reaction between the starting powder occurs, the reaction propagates spontaneously throughout the precursor from heated side to another. The blowing process takes place at the same time as the reaction propagates. The blowing behavior of Al-Ni precursors is self-sustainable, once the heated side of the precursor is reacted. The reaction starts at the melting point of aluminum and combustion temperature exceeds the melting point of Al_3Ni.The precursor expands during this high-temperature period. Adding the foaming agent is effective to make pores in the synthesized product. However, the effect is not sufficient enough to achieve high porosity. Preheating the precursor before ignition is quite effective to produce the Al-Ni intermetallic foam with high porosity. By preheating the precursor, high porosity (>90 percent) can be achieved.
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