Application of Ultrasonic Image to the Evaluation of Temperature Distribution in Metal Powder Compacts During Spark Plasma Activated Sintering

Abstract

Spark Plasma Activated Sintering, SPAS, is a newly developed sintering method for both metal and ceramic powders. An advantage of the SPAS is that a powder can be consolidated in a very short time within several hundreds seconds, because the powder is pressurized in a mold and is heated by direct electric resistance heating of the powder, using pulsative electric current. Another advantage of the SPAS is that the sintering temperature is lower than conventional sintering methods such as hot press and HIP. For instance, a titanium-aluminide powder has to be sintered at 1473K by HIP, while well sintered at 1223K by the SPAS. However, so called “sintering temperature” of the SPAS is usually measured at the mold in place of the powder itself, because direct measurement of the powder’s temperature is much difficult from a technical point of view. It is considered that the powder is heated more rapidly than the mold and therefore the heat flows from the powder to the mold during sintering. Consequently, a temperature distribution is generated in the powder and therefore “true sintering temperature” cannot be clear.