Thermomechanical Formation of the Internal Surfaces of Waveguide System Couplings

A method has been developed for forming a complex connecting element with an internal surface (rectangular coupling) for a waveguide system pipe made of a shape memory alloy. The proposed method is based on the high-precision formation of a complex internal surface by restoring pre-deformed dimensions through a phase transition upon heating, followed by heat treatment above the recrystallization temperature of the connecting material (over 400°C) and maintaining the required shape. The method of plastic self-forming of complex asymmetric internal surfaces in parts made of shape memory alloys involves the following steps: fabrication of a mandrel tool from a structural material, featuring high surface finish and precision, with external dimensions mirroring the size and configuration of the finished part; production of a workpiece with a smooth internal surface, smaller in size than the final part made of a shape memory alloy; cooling the workpiece below the direct martensitic transformation temperature of the material; deforming it using the mandrel tool; heating the workpiece together with the mandrel above the reverse martensitic transformation temperature, resulting in restoration of the initial dimensions of the part and filling of the relief cavities with the coupling material onto the mandrel outer surface; fixing the material memory by heat treatment at a temperature above the recrystallization point followed by holding; and cooling below the direct martensitic transformation temperature and removing the mandrel tool. At temperatures below the recrystallization temperature, the parts are found to undergo plastic deformation, polishing, and heat treatment by applying external stress. The proposed method can be recommended for connecting pipelines in waveguide systems, ensuring their tightness under high magnetic impermeability of the gap and excess pressure differentials of up to 0.2 MPa.