Synopsis:Recently the investigations on the local stress/strains and related properties in the engineered superconducting composites have been extensively carried out by using the pulsed neutron facilities, J-PARC TAKUMI. Firstly the key concepts are described in order to understand their mechanical-electromagnetic properties after the performance of TAKUMI is briefly introduced. Unique and important results have been obtained by the present diffraction studies. Highlights of the present review are the three dimensional description of strains in Nb 3 Sn filaments, the determination of force free strains at RT and 77 K for BSCCO and YBCO tapes, and of T o for the BSCCO tape and Nb 3 Sn wires, which is the initiation temperature of thermally induced residual strains. Typically the local axial strain exerted on Nb 3 Sn filaments has been firstly measured along the TF coil used for ITER project in the world.

In this study, the microstructure of hot-extruded and under-extruded Zr bearing aluminum alloys Mesoalite10 ®-1.3 mass%Zr was investigated by high-resolution EBSP analysis and the effect of Zr addition on microstructure formation during hot extrusion was studied. In an extruded Zr free alloy, coarse fibrous grains elongated to the extrusion direction were predominantly evolved. And these grains were considered to be formed by elongation of the original equi-axial grains by extrusion. Whereas, in extruded Meso10-1.3 Zr alloy, many fine grains were evolved near the grain boundaries of the fibrous grains. In under-extruded Meso10-1.3 Zr alloy, inhomogeneous local strains were developed near random grain boundaries and new fine grains were formed by continuous dynamic recrystallization. It is considered that in aluminum alloys, the addition of Zr promotes continuous dynamic recrystallization during hot extrusion.

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Metastable precipitates play important roles in a super high strength Al-Zn-Mg based alloy Mesoalite ®. The present study was undertaken to examine the composition of the metastable precipitates in Mesoalite ® and the effect of Mn addition on the composition. The Zn+Mg concentration of hЈ metastable precipitates detected by 3DAP three dimensional atom probe was ϳ25% in the alloy Al-4.1Zn-3.1Mg-0.57Cu-0.01Ag at%. By comparing with the results of G.P. zones in an Al-Zn alloy, it was suggested that the intrusion of Al atoms from the matrix lowered the Zn+Mg concentration of metastable precipitates detected by 3DAP. A model to quantify the intrusion of Al atoms was developed and applied to the metastable precipitates. The Zn+Mg concentration was quantified to be ϳ65 at% at 383 K and ϳ75 at% at 413 K. When the alloy contained Mn, furthermore, it was suggested that Mn affected the Zn/Mg ratio of metastable precipitates by lowering the virtual Zn/Mg ratio of the specimen composition.

The stress corrosion cracking SCC resistance of hot-extruded P/M Al-Zn-Mg alloys, Mesoalite, was investigated as compared with that of I/M Al-Zn-Mg alloys and the correlation between stress corrosion resistance and microstracture was studied. SCC resistance about P/M alloys was high as compared with that of I/M alloys and when the solute concentration increased, reduction of SCC resistance about P/M alloys was not observed. The difference in width of PFZ, distribution of precipitates on grain boundary, the amount of metastable phase precipitated in the matrix, tilt angle of grain boundary, grain size and shape was investigated as a cause of the difference of SCC resistance. The large change in the size and shape of grain among these factors was observed. In the P/M alloys, the fiber-like grain elongated to the extruded direction was observed to the equi-axial grain having been observed in the I/M alloys. When stress was applied parallel to elongated grains, the stress perpendicular to the grain boundary was low. Since the SCC resistance is improved when the applied stress perpendicular to the grain boundary is small, it is concluded that the SCC resistance of the P/M alloys which has the fiber-like grain elongated to the ED became large.