In the middle of the 19th century, the Englishman H.C. Sorby first observed the metallographic structure of hardened steel with a microscope, and later named this needle-like structure martensite.
The figure below shows the metallographic structure of the high carbon steel in the quenched state. The needles (the space shape of which is plate-like) is martensite, and the base is retained austenite.
In the 1920s, American Fink (W.L.Fink) and Soviet man Kurdyumov (Г.В.Курдюмов) used X-ray diffraction technology to determine the nature of martensite in steel: body-centered square structure, carbon Supersaturated solid solution in a-Fe, a metastable phase that austenite transforms into under non-equilibrium (large undercooling) conditions.
By the 1950s, not only accumulated a large amount of technical information on martensitic transformation in steel, but also found that a similar transformation occurred in a series of non-ferrous alloys and some pure metals. On this basis, it is gradually recognized that the phase transformation represented by the formation of martensite in steel is a solid-state first-order phase transformation that is essentially different from the solid-state diffusion-type crystal transformation that has always been understood—the non-diffusion crystal type transformation, named as martensitic transformation.
The low-temperature products formed by martensite transformation in various alloy systems are called martensite, such as martensite in titanium alloys and martensite in copper alloys. Martensitic transformation is one of the basic types of phase transformation that occurs during metal heat treatment, and it is of great significance to the strengthening heat treatment of steel and the application technology of shape memory alloys.
