MECHANICAL PROPERTIES OF COLD-ROLLED AND AGED MP35N ALLOYS FOR CRYOGENIC MAGNET APPLICATIONS

MP35N is a Nickel-Cobalt based superalloy that currently has numerous applications at both room and elevated temperatures due to its ultra high strength, high modulus and outstanding corrosion resistance. The National High Magnetic Field Laboratory (NHMFL) further explored the use of MP35N in cryogenic temperature applications. Currently, the material is used as a structural reinforcement component for high field pulsed magnets operating at 77 K. The NHMFL is also pursuing the application of MP35N below 77 K, such as either reinforcement or substrates for high-temperature superconducting (HTS) magnets operating at 4.2 K. This paper reports the tensile properties of cold-rolled and aged MP35N at room temperature, liquid nitrogen and liquid helium temperatures. Optimized fabrication methods developed by the NHMFL and H. C. Starck have improved the material's cryogenic properties with ultimate tensile strengths exceeding 2500 MPa and a modulus of elasticity higher than 200 GPa. Closer examination of the stress-strain curve reveals that the material exhibits internal stress which is attributed to the development of nanoplatelets during the fabrication process.