Thermal expansion and phase transformations of low-expanding cobalt-iron-chromium alloys

Abstract

Coeffi cients o f lineal' t hermal ex pansion of some cobalt-i ron-chromium alloys are reported for variou s tempe mture ranges between-65 0 and + 800 0 C, and the effects due to temperature , chemical composition, hea t treatment, etc., were determin ed. Some of t he a lloys investigated hav e coefficien ts of ex pansion less than t hose for fu sed quartz and ordinary inval' between-65° and + 60 0 C. Some of the low-expand ing cobalt-iron-chromium alloys have ')'-> a t ran sformation s on cooling to low temperatures, and t he resulting a-phase reverted to 'Y on heating t o hi gh temperatu res. AI'" tempera tu res were observed as high a s _ 10 0 C ancl Ac, tempemtures at abou t 600 0 C. The effects of various hea t treatm ents from-196° to + ] ,000 0 C on t he t ran sforma t ion s were investigated , and the res ultillg changes of thermal ex pansion were correlated wi t h t he structlll'e of these alloys.