Cu-Nb and Cu/stainless steel winding materials for high field pulsed magnets

Abstract

1 h promising types of CuiStrinless Steel (SS) inrcrocoiiipositc and Cu-Nb microcomposite winding wircs for lnrge scnled tiigli ficld pulscd mngiicts nrc reviewed.l'hc cstiination o f tlic potentially nchicvnble combinations of mechanical and electrophysicat properties has bceri done. Thc fcatrires o f corresponding manufncturing proccsses foi' CulSS and Cu-Nb wircs arc prescnted. The strength -conductivity propcrtics o f severi4 types of Cu-Nb and CulSS conductors nre given. nolationships Iicfrvcon the microstructure parnmctcrs nnd mechanical pmpcrtics of Cu-Nb wircs arc discusscd. TI*:RT(Room tempcrrture) ultimatc tansilestrength fit thc level of900-1100 MPa and conductivity 50-60% IACS for CulSS conductors with cross-sections up to 40 mm' has bcen attnincd. For Cu-Nb Arcs with 6 nim' cross section the 1 U ultimnte strength cxcccding l4OOMPe hasbeenattained. I. INIXODUCTIONThere are a number of Projects aimed for a devcloptnent of cxtremely high field pulsed magnets [I]. These magnets dcsigned to create magnctic fields higher than 70 T could be cronomically eficientancl couldprovjdc the pulses of field with lengths typically 10 to 100 ms. One of the most important issue to bc resolved for achieving the success in development of cxtremely high field magnet systems is the development of suitablc winding wires with unique combination of mechanical strength and conductivity. The possible candidates for applicatioii as high strength, high conductivity winding wires are dispersion strengthened copper [2], macrocomposite Cu/Stainless Steel wires [5j an&microcompositc wires on the base of Cu-Nb [3], Cu-Ag [4]. Investigation and analysis o f some aspccts of possible fabrication proccsses of various advanccd high strength high conductivity conductors has bccn themain goal ofthis prescntntion. A. Macrocomposite Cti/SS condii ctwx Development oFCu/SS wires has already a long history. This conductor was pioneered by Oxford, Clorendon Laboratory more then 15 years ago {6]. Macrocomposite CiiiSS wires seem to not be a very sophisticated matcrial. An initial billet represents a coppercoi'e surroundedby ajacket of stainless steel. Manuscrip reccived Scptcniber 27, 1999. Victor I. Pantsyrnyi SSC RT: Bochvar Rcsearch Insiiliitc of Inorganic Matcrials P.0. BOX 369, Moscow 123060, h i s s i n Teleplionc: (095) 190-82-50, rax: (095) 196-67-01 E-mail: viiiii~m.400~g23.rcIcom.r11 Ultimate tensile strength (UTS) of high piirity annealed Cu equals only to 200-230 MPa. That is why the realimtion of necessary conductor strength could be attained altnost entirely by SS. Taking into account that the characteristic dimensions or SS and Cu components in cross section of this wirc are 2 lp m oiie can apply well known Rule Of Mixhirc (ROM) for calculating of the composite conductor strength and conductivity. The rcsiilts of strength calculations show thsll lor attaining nccessary values of wire strength (1 100-1300 MPa) at 50-60% IACS conductivity (at room temperature) the Ul'S ol' SS component sliouldbc in Ihcrangeof2000-3000 Ml'a,It should bc...

Effects of size and geometry on the plasticity of high-strength copper/tantalum nanofilamentary conductors obtained by severe plastic deformation

“…Up to now, reinforced copper-based wires have shown the best compromise between these two criteria; in particular, the copper/niobium (Cu/Nb) system has been studied for decades since it has very good mechanical properties that are much better than rule-of-mixture (ROM) predictions when the size of the Nb filaments is reduced to the sub-micrometer range. It should be emphasized that two main fabrication routes have been studied: production of nanofilamentary Cu/Nb wires via severe plastic deformation (SPD) of: (i) arc-melted Cu-Nb ingots, initially consisting of a Cu matrix containing Nb dendrites, so-called ''in situ'' composites; and (ii) bulk Cu tubes and Nb rods, giving rise to a Cu matrix containing Nb continuous filaments, so-called ''continuous'' composites [2][3][4][5][6][7][8][9][10][11][12][13].…”

Investigation on the CuNb "in-situ" microcomposites conductivity during the process of tensile testing

“…The stressed condition of the crystallographic lattices of the components in Cu-Nb microcomposite material has been confirmed by X-ray analysis [13]. In particular it has been shown that crystallographic lattice of copper is compressed in longitudinal direction parallel to the axis of deformation by drawing and consequently is stretched in the transverse direction.…”

Microstructure and fatigue strength of high-strength Cu–Fe and Cu–V in-situ nanocomposite wires

“…These alloys were prepared by vacuum arc melting using a consumable electrode and subsequently enclosed in a copper case and subjected to cold drawing deformation with intermediate annealings at 350-500°C. The preparation procedure of the nanocomposite conductors by melting followed by cold deformation and results of the study of their electromechanical properties are described in [4,19,20]. The total degree of cold deformation by drawing for samples subjected to fatigue tests was ln (A 0 /A) = 7-9, where A 0 and Across sectional area of the sample before drawing and after drawing, respectively.…”