Mechanical properties of powder-in-tube processed mono- and multi-filamentary Bi2223 tapes

In order to establish a standard technique for testing the tensile properti es of the Ag sheathed Bi2223 tapes, their microstructure dependence has bee n investigated. The tapes consisting of mono-oxide filament shows a three s tage behavior. The first elastic region (stage I) is very narrow and follow ed by the stage II, where the slope of stress-elongation curve decreased gr adually. Then the macroscopic yield and the plastic deformation region (sta ge III) appeared, where the multiple cracking phenomenon was observed. Simu ltaneously the change of electric voltage was monitored. The voltage turned on to increase from the beginning of stage II and its increasing rate acce lerated in the stage III. Their change is related to the formation of micro cracks and the macroscopic fracture in the oxide layer, respectively. The t ensile property of the multi-filamentary tapes revealed essentially the sam e three stage behavior. Stage II was enlarged, because the initial fracture stress increased due to the strengthening of the Ag alloy matrix. The mult iple fracture at stage III was not remarkably observed. According to the VA MAS program, the tensile test has been carried out by eight research groups by using the common specimens. Their results were analyzed and discussed i n order to reproduce the accurate results. (C) 2001 Elsevier Science BN. Al l rights reserved.