Tensile properties of L12 intermetallic foils fabricated by cold rolling

Polycrystalline L1(2)-type Ni-3(Si,Ti), Ni2Al and Co3Ti alloys prepared through thermomechanical processing from arc-melted ingots were Successfully cold-rolled to thin foils with a thickness of less than 200 mu m. The cold-rolling with over 90% reduction in thickness was possible without providing intermediate annealing. The cold-rolled foils showed high tensile strength (similar to 2 GPa) at room temperature although no plastic elongation was observed. The tensile strength of the annealed foils generally decreased acquiring a certain level of fracture strain. Room temperature fracture strain increased with increasing annealing temperature, and reached to 30-40 % by a high temperature annealing at 1173 K. Among three kinds of intermetallic alloys, the Ni-3(Si, Ti) foil annealed around at 900 K exhibited an extremely high tensile strength and yield strength (over 2 GPa) with a reasonable fracture strain. Also, it was found that the fully-recrystallized Ni-3(Si, Ti) and Co3Ti foils showed a strength anomaly at intermediate testing temperature. The observed tensile properties, especially tensile strength at low temperature as well as at high temperature for the present L1(2) intermetallic foils, were found to be superior to those for the conventional alloys Such as nickel based alloys and stainless steels.