bimetalls

Bimetalls, or bimetals, refer to systems in which two distinct metals are bonded together to form a single component. In such constructions, the two metals retain their individual identities and properties, while the combination yields a material or object with a blend of characteristics that neither metal alone would provide. The bond can be achieved by processes such as cladding, bonding, or mechanical assembly.

In currency and coinage, bimetallic design has been used to enhance security and durability. A bimetallic coin typically features two different metals or colors in its structure, for example a central disc of one metal surrounded by a ring of another. This approach has been employed in various national currencies, including some euro coins and circulating coins from other countries, to deter counterfeiting and to create visually distinctive denominations. Beyond coins, the term bimetallism historically described monetary systems that used two metals, commonly gold and silver, as legal standards for value. Such systems were widespread in the 19th century in particular but gradually gave way to monometallic standards or fiat money in the following decades.

In engineering and measurement, bimetallic strips are widely used components. They consist of two metals with different coefficients of thermal expansion bonded together. When temperature changes, the strip bends due to unequal expansion, a principle exploited in thermostats, temperature sensors, and automatic switches. The combination of metals allows a single component to respond to heat in a predictable way.

Fabrication of bimetals involves methods such as bonding, cladding, or diffusion bonding, and considerations include interface strength, corrosion resistance, and potential galvanic reactions between the metals. Bimetals remain a practical approach to combining desirable properties from two metals in a single piece.