Extrusion-activated thermal explosion applied to intermetallics processing

Abstract

The present study deals with synthesizing the NiAl compound through the thermal-explosion route akin to self-propagating high-temperature synthesis under the novel circumstance of extrusion-induced mechanical activation. Either route has the potential for addressing the intermetallics processing cost problem and both reactions may alike be significantly enhanced by prior activation. Reactant powders were homogeneously mixed and precompacted by cold isostatic pressing (CIP) at 800 MPa. Hydrostatic extrusion was performed with a lower-chamber pressure fixed at 50 MPa and an upper-chamber pressure of 1.4 GPa, hence yielding a fully dense Ni+Al mixture, maximizing the contact areas between reactants and enhancing the specific surfaces of Al without such a grain refinement as with mechanical activation by ball milling. After heating up to 550 ^°C with a rate of 10 ^°C/min, uniquely CIPed samples did not react, whereas those subsequently extruded did react in the thermal-explosion mode with temperature overstepping 1084 ^°C.

Keywords:

• intermetallics
• extrusion
• mechanical activation
• powder metallurgy