Alloy 42. A nickel-iron controlled-expansion alloy containing 41% nickel. It has a low and nominally constant coefficient of thermal expansion from room temperature to about 300°C. Used for glass-to-metal sealing ofponents that are enclosed in a glass envelope, such as lamps and electron tubes. Alloy 42 Chemical Compositions:Nilo® 42 (Also known as Alloy 42, Invar 42, UNS K94200, UNS N94100, Dilaton41, FeNi36, 64FeNi) is an iron-nickel controlled expansion alloy containing 42% nickel with a low and nominally constant coefficient of thermal expansion in …42 Alloy Low Expansion Stencil Grade Alloys ASTM F30. 42 Alloy, a low expansion alloy, is very similar to Invar 36 with a slightly different Coefficient of Thermal Expansion. This nickel-iron alloy is ideal for lid, lead frames, stencil/etching, telmunications and aircraft industry, offering a more affordable alternative to Kovar when a tight seal is not required.