Semiconductor sensors which detect forces or displacements should preferably be used with an elastic metal having a small coefficient of thermal expansion.
The present investigation is concerned with elastic alloys with low thermal expansion coefficients. The alloys contain iron, nickel and cobalt with proper ratios, and their elastic properties can be adjusted by applying cold working and heat treatment.
The elastic properties of several metals of low thermal expansion coefficients are examined by the stress to plastic strain method, and then the elastic property of the iron-nickelcobalt alloys is evaluated in detail by the internal friction method.
The tensile strength of an iron-nickel-cobalt alloy is increased to 1800MPa when the nickel content is less than 28%. However the most suitable composition for use of the semi conductor sensors is 28.7∼30% of nickel and 17∼18% of cobalt. In this case, the thermal expansion coefficient is less than 50×10^-7/K, the tensile strength is about 1100MPa and the elasticity is the same as that of a beryllium-copper alloy.