Magnetoelastic effect during the low-temperature deformation of 316LN-IG stainless steel

The segments of tubes made of austenitic 316LN-IG stainless steel that are cut along the tube axis are subjected to tensile tests in liquid and gaseous helium at temperatures below 7 K. The tubes are intended for the conductor conduits of the toroidal magnetic system of ITER. The time evolution of the strain, the temperature, and the strain-induced magnetization of specimens in the form of the normal component of the magnetic field on their surfaces is studied as a function of the applied load. The behavior of local deformation near slip bands is complicated: the areas near slip planes undergo unloading and shrinking. A magnetoelastic effect is detected; it indicates a negative longitudinal magnetostriction for the initial $\beta$ phase and the strain-induced $\alpha$ phase. The cases of absent local heating during strain jumps are explained by the magnetocaloric effect in the areas unloaded during slip.