Sintering aluminum alloy powder using direct current electric fields at room temperature in seconds

The sintering of a metallic alloy powder into bulk form using only direct current (DC) electric energy input at ambient room temperature is presented for the first time. It was found that a flash sintering phenomena is achievable in aluminum alloy powder, with no addition of external thermal energy, at applied DC electric fields in the range of 175–330 V/cm in which the formation of interparticle necks occurs rapidly and is characterized by a near-instant change in the physical properties of the compact from electrically non-conductive to electrically conducting in a time period on the order of seconds. It was found that the kinetics of this effect have a logarithmic dependence on the magnitude of the applied electric field. Above approximately 330 V/cm, the critical field strength is reached at which an incubation time for flash sintering is not required and sintering occurs instantly with the application of the DC field. This technique has promise to greatly reduce processing time and costs associated with sintering of powder metallurgy products as well as consolidation of nanostructured metals by limiting exposure to high temperatures which result in excessive grain growth.