Abstract
The authors formerly found out that intercurrent introduction of nitrogen gas into the milling atmosphere during mechanical alloying of Ti-Al powder mixture promotes the synthesis of alloy powder and named this process "nitrogen shock mechanical alloying". It was confirmed by x-ray diffraction analysis that nitride, Ti2AIN was formed in sintered bodies of the alloy powder synthesized by the nitrogen shock MA. It is expected that TiAl matrix can be strengthened by the nitride, if the nitride precipitates in the form of fine particles dispersed in the matrix.
In this study, the nitrogen shock MA was applied to a mixture of Ti, Al and B powders to make a Ti-Al-B alloy powder and the alloy powder was consolidated by spark plasma activated sintering, in order to investigate effects of nitrogen on the microstructure and properties of sintered bodies. Boron was added in expectation of the formation of fine TiB2 particles which strengthen the matrix as well as the nitride. As a result, it was found that nitrogen taken in the alloy powder enhances amorphization of the powder. It was also found that the nitride increases hardness and Young's modulus of the sintered bodies. However, the nitride formed excessively made the microstructure of the sintered bodies uneven.
