Lattice-parameter variation with carbon content of martensite. I. X-ray-diffraction experimental study

An experimental law of the x-ray diffraction of polycrystalline martensite is found, which is satisfactorily explained from x-ray-diffraction theory. The experimental phenomenon is well consistent with the hypothesis that at low carbon content martensite is of cubic structure. The cubic-tetragonal transition of martensite concerned with the distribution of carbon atoms is observed, and an experimental critical point of the transition is also obtained. Dependences of the lattice parameter of low-carbon martensite upon carbon content are established. With the dependences, it becomes possible to determine the carbon content of the carbon-supersaturated \ensuremath{\alpha}-phase of steel.