The Joints Properties of TiAl and AISI4140 by Friction Welding Method

摘要

The microstructural change and mechanical properties of friction welded TiAl alloy/AISI 4140 joint have been investigated with various friction welding conditions for example friction time, friction pressure and upset pressure. At the peripheral side of the joint, crack was observed because of brittle nature of TiAl and internal stress of transformed martensite. This defect cannot be avoidable and deteriorated the mechanical property of the friction welded joint. The microstructure of weld zone was composed of TiAl lamellar structure, TiC, recrystallized fertile and fine pearlite. Remarkable microstructural variation was observed at the AISI 4140 part. Fine pearlite structure of AISI 4140 base metal was transformed to the lath-like martensite and fine pearlite during thermal cycle of friction welding. The hardness profile of the joint showed higher value those of the TiAl and AISI 4140 base metal. This result may be occurred by the intermetallic compound and the martensite transformation. The tensile strength showed approximately 120MPa which was lower value relative to those of other joining method due to the crack existed in the peripheral joint. To improve the mechanical property of the friction welded joint, it is needed to prevent the formation of the crack inserting materials act as the buffer.