브레이징법에 의한 TiA1 금속간 화합물의 접합에 관한 연구

Abstract

본 연구에서는 Al을 삽입금속으로 사용하여 브레이징법으로 접합한 TiAl 금속간화홥물의 접합특성에 대하여 조사하였다. 삽입금속인 Al과 모재인 TiAl과의 반응에 의해 접합계면에서는 반응생성층으로서 경도가 모재보다 높고 취약한 TiAl₃가 형성되었으며, 접합온도가 600℃로 낮았거나 가열속도가 30K/min으로 너무 빠를 경우에는 반응생성층내에 void와 미소균열과 같은 접합결함이 존재하였다. 이와 같은 접합결함들은 700℃보다 높은 온도에서 접합하거나 가열속도를 10K/min보다 낮게 하여 접합한 경우에는 나타나지 않았다. 한편 접합체의 기계적 성질의 향상을 위하여 접합 후 Ar가스 분위기에서 열처리를 행한결과, 1300℃에서 3시간 동안 열처리를 했을 경우 모재와의 조성의 균일화가 완전히 이루어지지 않았으며 또한 반응생성층의 형태도 변화가 없었다. 그러나 1350℃에서 3시간 동안 열처리한 결과 조성의 균일화와 함께 반응생성층은 ??단상으로 변하였으며, 반응생성층의 미소경도는 층상조직인 모재의 미소경도보다 조금 낮게 나타났다.

In this study, Joining properties of TiAl intermetallic compound bonded by brazing method using an insert metal of Al foil were investigated. A brittle reaction product layer. TiAl₃was formed at the joining interface and its microhardness was very higher than that of base metal. When the specimen was bonded at low temperature of 600℃ or with high heating rate of 30K/min respectively, joining defects like void and micro-crack were formed in the in the inside of reaction layer. These joining defects were disapeared when the speciment had been bonded at higher temperature than 700℃ or with lower heating rate than 10K/min. For the purpose of improving the mechanical properties of joints, effects of the post-bond heat treatment in Ar gas atmosphere on microstructure and hardness distribution of the bonded speciment were studied. When the joint was geat-treated at 1300℃ for 3 hr, homogenization of the compositions in the joining interface region was not achieved completely and morpholgy of the reaction product layer was still remained without morphological change. However, when the joint was heat-treated at 1350℃ for 3 hr, homogenization of the compositions in the joining interface region was achieved and the reaction product layer changed to γ single phase. And micro-vickers hardness of reaction layer region was slightly lower than that of base metal.

In this study, Joining properties of TiAl intermetallic compound bonded by brazing method using an insert metal of Al foil were investigated. A brittle reaction product layer. TiAl₃was formed at the joining interface and its microhardness was very higher than that of base metal. When the specimen was bonded at low temperature of 600℃ or with high heating rate of 30K/min respectively, joining defects like void and micro-crack were formed in the in the inside of reaction layer. These joining defects were disapeared when the speciment had been bonded at higher temperature than 700℃ or with lower heating rate than 10K/min. For the purpose of improving the mechanical properties of joints, effects of the post-bond heat treatment in Ar gas atmosphere on microstructure and hardness distribution of the bonded speciment were studied. When the joint was geat-treated at 1300℃ for 3 hr, homogenization of the compositions in the joining interface region was not achieved completely and morpholgy of the reaction product layer was still remained without morphological change. However, when the joint was heat-treated at 1350℃ for 3 hr, homogenization of the compositions in the joining interface region was achieved and the reaction product layer changed to γ single phase. And micro-vickers hardness of reaction layer region was slightly lower than that of base metal.