Stress/Strain Characteristics of PIT MgB2 Tapes with Ni Sheath

Abstract

Þâèåwåw@ ¶(Graduate Student, Iwate University) ú{à®wï ae 68 ª ae 9 (2004)642_ 647 ÁWu´`±Þ¿\Þ¿Èw©çÀp»ÜÅv jbPV[X PIT @ MgB 2 e[vÌÍ/иÝÁ« The stress/strain dependence of critical current and the mechanical properties of nickel sheathed PIT MgB 2 mono_ core tapes with various kinds of metal powders addition to the core were evaluated at 4.2 K in the magnetic field of 2 T. No marked change in the stress_ strain curve was found by the powder addition. The critical current was markedly enhanced by In and Sn powder addition. The critical current was almost constant irrespective of strain up to the irreversible strain where a steep degra dation of critical current begins. The irreversible strain for the tape increased from 0.25 to 0.50÷ by the addition of In and Sn powder. The In addition also suppressed a slight increase in the critical current with strain. The effects of Ag and Cu addition are less as compared with those of the low melting point metal powder such as In and Sn. SEM observations on the longitudinal sec tion of In added tape after the tensile test clarified that the cracks were few and rather large as compared with those in the tapes with no addition or high melting point metal powder addition. The strain characteristics were compared with those of MgB 2 with other sheath materials and those of a conventional Nb 3 Sn wire. (Received April 15, 2004; Accepted June 16, 2004) Keywords: MgB 2 tape, metal powder addition, mechanical property, critical current, strain dependence, irreversible strain

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