Near-net forming of porous Co-Al by isothermal treatment: Phase formation sequence and diffusion kinetics

Porous CoAl 3 intermetallics have great catalytic potential. However, its high porosity and controllable preparation are still incipient. In this paper, the effect of isothermal treatment on the near-net formation process of porous CoAl 3 material is studied, and the phase transformation process and diffusion kinetics of the Co/Al diffusion couple in the solid-phase diffusion stage are described. The results show that isothermal treatments in the range of 510–550 °C reduce the exothermic intensity of the thermal explosion (TE) reaction. The holding time of 30 min at 530 °C facilitates the near-net formation of porous CoAl 3 . The isothermal treatment does not affect the phase composition of the final product. Still, it causes changes in the phase and depth of the diffusion, affecting the exothermic strength and skeleton morphology. Based on the phase transition and thermodynamic analysis , the CoAl phase formation is the key to reducing the exothermic intensity. The diffusion kinetics indicates that the low diffusion activation energy of the CoAl phase (Q 1  = 1.66 kJ mol −1 ) is the main reason for the preferential formation. And the exponential kinetic factor of the second diffusion layer (n 2  = 0.75) explains its high diffusion depth.