Abstract
The self-propagating foaming process of porous Al-Ni intermetallics was investigated. Aluminum and nickel powders were blended, and titanium and boron carbide powders were added as reactive exothermic agents. The blended powder was extruded to make a rod-shape precursor. Only one end of the rod precursor was heated to ignite the reaction. The reaction propagated spontaneously throughout the precursor. Pore formation took place at the same time as the reaction occurred. Adding the exothermic agent was effective to increase the porosity. Preheating the precursor before the ignition was also very effective to produce porous Al-Ni intermetallics with high porosity.
Highlights
Porous metals exhibit various unique physical and mechanical properties, such as low apparent density, low thermal conductivity, high specific stiffness, gas permeability and high strain energy absorbing capacity [1]
Titanium and B4C powders were added as reactive exothermic agents, which increases the heat of reaction
When the precursor is heated, the exothermic reactions between (1) nickel and aluminum [15,16] and (2) titanium and B4C [17] shown below take place: 3Al + Ni Æ Al3Ni + 151 kJ/mole Ni
Summary
Porous metals exhibit various unique physical and mechanical properties, such as low apparent density, low thermal conductivity, high specific stiffness, gas permeability and high strain energy absorbing capacity [1]. The authors have developed an innovative fabrication process for porous intermetallics using combustion synthesis, and reported porous Al-Ni intermetallics with porosities of more than 80% [11,12,13,14]. In this technique, porous Al-Ni intermetallics were fabricated by heating a reactive precursor consisting of aluminum, nickel, titanium and boron carbide (B4C) powders. When the precursor is heated, the exothermic reactions between (1) nickel and aluminum [15,16] and (2) titanium and B4C [17] shown below take place:
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