U. Stuhr

Plasticity of multiscale nanofilamentary Cu/Nb composite wires during in situ neutron diffraction: Codeformation and size effect

In situ neutron diffraction was performed on Cu∕Nb nanocomposite wires composed of a multiscale Cu matrix embedding Nb nanofilaments with a diameter of 267nm and spacing of 45nm. The evolution of elastic strains and peak profiles versus applied stress evidenced the codeformation behavior with different elastic-plastic regimes: the Cu matrix exhibit size effect in the finest channels while the Nb nanowhiskers remain elastic up to the macroscopic failure, with a strong load transfer from the Cu matrix onto the Nb filaments. The measured yield stress in the finest Cu channels is in agreement with calculations based on a single dislocation regime.

In situ neutron diffraction under tensile loading of powder-in-tube Cu∕Nb3Sn composite wires: Effect of reaction heat treatment on texture, internal stress state, and load transfer

The strain induced degradation of Nb3Sn superconductors can hamper the performance of high field magnets. The authors report elastic strain measurements in the different phases of entire non-heat treated and fully reacted Nb3Sn composite strands as a function of uniaxial stress during in situ deformation under neutron beam. After the reaction heat treatment the Cu matrix loses entirely its load carrying capability and the applied stress is transferred to the remaining Nb–Ta alloy and to the brittle (Nb–Ta)3Sn phase, which exhibits a preferential ⟨110⟩ grain orientation parallel to the strand axis.

Residual Strain in a

The strain dependence of the critical properties of Nb3Sn superconducting strands is a major complication for critical current (Ic) measurements. We report neutron diffraction measurements that have been carried out at room temperature and at 10 K in order to determine the strain state of a Nb3Sn powder-in-tube (PIT) strand mounted on a critical current measurement barrel made out of a Ti-6Al-4V alloy.

{\rm Nb}_{3}{\rm Sn}

Copper-based high strength nanofilamentary wires reinforced by bcc nanofilaments (Nb or Ta) are prepared by severe plastic deformation for the winding of high pulsed magnets. In-situ tensile tests under neutron beam were performed on a Cu/Nb nanocomposite composed of a multiscale Cu matrix embedding 55 4 Nb filaments with a diameter of 267 nm and spacing of 45 nm. The evolution of elastic strains for individual lattice plane in each phase and peak profiles in the copper matrix versus applied stress evidenced the co-deformation behavior with different elastic-plastic regimes and load sharing: the Cu matrix exhibits size effect in the finest channels while the Nb nanowhiskers remain elastic up to the macroscopic failure, with a strong load transfer from the copper matrix onto zones that are still in the elastic regime. Taking into account results from residual lattice strains also determined by neutron diffraction, the yield stress in the finest Cu channels is in agreement with calculations based on a single dislocation regime.