Ordered intermetallic alloys possess many attractive properties, yet their use as a structural material has been severely limited by a general lack of low temperature ductility. The beta/gamma-prime dual-phase Ni50Fe30A120 (atomic percent) intermetallic alloy has shown remarkable ductility, exhibiting fracture strains in excess of 20% in both tension and compression. This behavior is yet unexplained, thus an investigation was conducted to study the deformation and fracture behavior of this alloy.The material studied was a Ni50Fe30A120 (nominal composition) directionally solidified alloy. TEM specimens were made from the as cast material in an unstrained condition and with a 1% strain in compression. The foils were hand ground to a thickness of about 75 um and electrothinned in a Tenupol twin jet polisher with a methanol-based solution containing 2% perchloric acid and 35% butyl cellosolve at -20C. A JEOL 2000 FX AEM was used to examine the strained and unstrained foils. STEM microanalysis was performed on the unstrained foil with a Phillips CM-12 AEM to determine the composition of the two phases. Finally, the compression fracture surface was studied using a Hitachi S520 SEM.
