Processing, microstructural characterization, and mechanical properties of deep cryogenically treated steels and alloys – overview

Deep cryogenic treatment (DCT), a technique of deep subzero processing, is utilized after quenching and well preceding tempering. In DCT, the materials are subjected to a soaking period of typically 24 h at a temperature of −196 °C. The optimal soaking period varies depending on the material to be cryotreated. The microstructural characteristics and mechanical properties of ferrous and nonferrous materials are significantly enhanced using DCT resulting in improved durability and functional performance of the mechanical components. The DCT is generally performed on tool steel, stainless steel, aluminum alloys, and magnesium alloys to improve its mechanical properties. The complete transition of residual austenite to martensite and finer secondary carbide precipitation correlates with an increase in the mechanical properties of tool steel. The nonferrous materials such as aluminum and magnesium alloys showed improved mechanical properties owing to the precipitation of finer second phases in the matrix. The main objective of this review paper is to provide an overview on the history and theories of DCT, important processing parameters, and the effect of DCT on microstructure and mechanical properties of tool steel, aluminum alloys, and magnesium alloys.