PURPOSE: To obtain a high intensive deformable element by adding Be or Ti and C to Fe-Ni base and using metal alloy deoxidied by Si and Mn.

CONSTITUTION: Composition of Fe-Ni alloy consists of 37∼45wt% of Ni and 0.3∼ 1wt% of Be and 0.5∼3wt% of ti are added thereto. Survival of Si should be less than 0.5wt% and 0.1∼2wt% of Mn survives. Less than 0.1wt of C contains and the rest is Fe but 0.1∼1wt of the one of Mo, Nb, Zr and W may be added if necessary. After cold working in more than 50% of working degree, age treatment is made at 350∼550°C. By this treatment, Fi-Ni base get desirable composition that Ni and Be or Ti metal compound emerge in austenite ground. By this constitution, deformable element having average thermal expansion coefficient less than 4×10-6/ °C, internal friction less than 1×10-4 and tensible strength more than 85kg/mm2 is obtained.