Investigation On Technology Of Vacuum Hot Roll Welding Of Invar Alloy And Pure Aluminum

The vacuum hot roll bonding (VHRB) was used to join Invar alloy and pure aluminum, and the interlayer was made of tantalum. The microstructure of interface and mechanical property of Invar/Ta, Ta/Al and Invar/Ta/Al are investigated. The interface microstructure were analyzed by means of Optical microscope, SEM, and EDAX. Peel strength and Bending property were also investigated by means of respective equipments.This paper discussed the relationship between deformation and the rolling position, and the effect of different deformation on the compression ratio distribution of the VHRB Invar/Ta, and Ta/Al. The results shows that the middle position of the work piece is favorable for deformation. Along with the deformation increasing, the compression ratio of tantalum and invar is increased , but the increasement of tantalum is less than that of Invar alloy. This is due to the deformation resistence of Ta increases faster than that of Invar alloy. As the deformation increases, the compression ratio of aluminum is increased by positive, but that of tantalum is decreased. This is due to the soften of aluminum. The VHRB was used to join Ta/Invar alloy with different deformation, at 900℃. Better property joint can be made when the deformation was 25%, and the peel strength was 13.9N/mm. No metallic compounds generated on the interface. When the compression ratio is low, the interface was straight-like; with compression ratio increasing, the interface was wavy and straight mixed. when the compression ratio is 8%, fracture analysis shows that the joining is mainly apply on the mechanic extrusion. when the compression ratio is 25%, the peel sthength increased apparently, the welding joint was broken with Ta matrix and the interface. The elements of the composite metal were interdiffused.The VHRB was used to join Ta/Al and (Invar alloy/Ta)/Al with different deformation, at 500℃. Better property joint can be made when the compression ratio was 55%, and the peel strength was 26.7N/mm, the interface of which was wavy. There are a number of burr-like materials on interface. When the deformation was 16%, fracture analysis shows that the welding joint broken mainly on the interface. When the compression ratio was 55%, the welding joint broken on matrix, the joining is mainly apply on metallurgical bonding. The bending properties were tested on the specimen of Invar alloy/Ta, Ta/Al, and Invar alloy/Ta/Al with different deformation. The bending angle is 180°. Results show that there were no broken on the interface of the joint.