HIGH-TEMPERATURE STRENGTH AND DUCTILITY OF L12-TYPE NI3AL-NI3MN INTERMETALLIC COMPOUND

The mechanical properties of L1//2-type pseudobinary intermetallic compound Ni//3Al-Ni//3Mn were investigated in relation to testing temperature and alloy composition. A positive temperature dependence of yield stress was found in manganese compositions lower than 15 at%, suggestive of the Kear-Wilsdorf mechanism, while a negative dependence was found in the high manganese alloys. The composition dependence of yield stress at room temperature in the low manganese alloys was attributed to the solid solution hardening while that in the high manganese alloys was attributed to imperfect ordering. The elongation exhibited a maximum around 700 K irrespective of compositions, while the maximum and minimum were observed approximately in 9 and 12 at% manganese alloys, respectively. The high values of elongation obtained in 20 and 25 at% manganese alloys were probably due to imperfect ordering. Both the temperature and composition dependences of UTS were quite similar to those of elongation. The fractographic observation showed that the more ductile specimen tended to fracture more transgranularly.