THERMAL EXPANSION AND PHASE TRANSFORMATIONS OF LOW-EXPANDING COBALT-IRON- CHROMIUM ALLOYS

Coeffi cients of lineal' t hermal ex pansion of some cobalt-i ron-chromium alloys are reported for various tempemture ranges between 65 0 and + 800 0 C, and the effects due to temperature, chemical composit ion, 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 to high temperatu res. AI'" tempera tu res were observed as high as _ 10 0 C ancl Ac, tempemtures at abou t 600 0 C. The effects of various hea t t reatments from 196° to + ] ,000 0 C on t he t ran sforma t ions were investigated, and the resultillg changes of thermal ex pansion were correlated wi t h t he structlll'e of these alloys.