NiTi shape memory alloy adding Al intermediate layer ultrasonic welding method

The invention discloses an NiTi shape memory alloy adding Al intermediate layer ultrasonic welding method. An NiTi shape memory alloy is overlapped, an aluminum foil is taken as an intermediate layer,vibration energy of ultrasonic welding equipment is transferred to a welding head, under the combined action of static pressure and mechanical vibration of the welding head, interfaces of the NiTi shape memory alloy and the aluminum foil are subjected to high-speed friction heat generation, plastic deformation and other behaviors, a NiTi oxide film is broken, metal atom combination is achieved, and thus welding is completed. According to the technical scheme, the problems that harmful intermetallic compounds are formed and joint phase components are obviously changed in a traditional fusion welding method are solved, the aluminum foil is taken as the intermediate layer, the mechanical property of an NiTi ultrasonic welding joint is improved, and obvious improvement is achieved in remaining the functional characte