Effects of Alloy Additions to 4–79 Molybdenum Permalloy

Publisher Website
Google Scholar
Abstract
It is generally agreed that to obtain highest initial permeability in 4–79 molybdenum Permalloy, one must cool the alloy at a critical rate through the atomic-ordering temperature range during the final hydrogen anneal. Chegwidden and Ashworth have shown that this rate decreases with decreasing nickel and increasing molybdenum. The purpose of this investigation was to determine the effects of small alloy additions to vacuum-melted 4–79 molybdenum Permalloy upon the optimum cooling rate (CRopt) and maximum obtainable initial permeability. Varying amounts up to 1% by weight of aluminum, chromium, niobium, tantalum, titanium, and tungsten were added to small vacuum-melted heats. The cast ingots were processed to 0.006-in.-thick strip from which were obtained ring lamination samples. These were annealed at 2150°F for 4 h in pure dry hydrogen and cooled at different rates between 14F°/h and an estimated 10 000F°/h through the ordering range (1112° to 572°F). Sixty-cycle ac initial permeability (u0) was measured at 40-G induction. It has been found that chromium, niobium, and titanium decrease the CRopt and increase the maximum obtainable u0, e.g., 0.62% chromium increases the u0 from 56 000 at a CRopt of about 3700F°/h to 94 000 at an CRopt of about 550F°/h; and 0.56% niobium increases the u0 from 51 000 at a CRopt of about 3700F°/h to 90 000 at a CRopt of about 1100F°/h. The optimum addition for the three elements is approximately 0.50% to 0.70%. Aluminum, tantalum, and tungsten at the levels studied have no appreciable effect on either the CRopt or the maximum obtainable u0.

This publication has 3 references indexed in Scilit: