Summary

Description

<p><strong>This first part of this effort </strong>investigated the iron-nickel binary system with varying nickel content over a range of CTE from 0.6ppm/°C to 10.0ppm/°C.  Figure 1 shows a comparison of calculated values of room temperature CTE for binary Fe-f(Ni) alloys based on the two gamma state ferromagnetic model for the face-centered cubic Fe-Ni austenite matrix, with one-hundred year old data from the experimental work of Guillaume.  Both the calculation and the early experimental data indicate that the CTE of Fe-Ni binary alloys vary continuously with nickel content in a smooth and predictable manner.</p><p><strong>The second part of this </strong><strong>effort</strong> determined experimentally the functional relationship between Ni content and CTE for the binary Fe-Ni system.  This was achieved by manufacturing a series of test alloys using high-precision melt metallurgical techniques.  The test alloys were heat treated by the Goddard Space Flight Center’s (GSFC) Materials Engineering Branch (MEB) and CTE coupons were machined by GSFC’s Advanced Manufacturing Branch.  Microstrain was measured as a function of temperature from 300K to 23K using the MEB interferometer.  Figure 2 shows an example of a secant CTE calculated from these microstrain measurements over the temperature range 10°C to 30°C.</p>