High temperature rapid registration X-ray diffraction has been applied while investigated the transformation of lath $\alpha $- martensite crystal ensemble of six orientations (one packet) into $\gamma $- phase numerous orientations crystal complex under carbon steel ((0.4\%C) heating at different rates (0.016-3000 K ^{-1}$). Phase transformations textures were observed at all heating speeds.
It has been established that austenite grain complex represents the assemblage of definite orientated crystals because of $\alpha -> \gamma $- transition developed according to Greninger-Troiano (G-T) orientation relationship (OR). The character of observed textures changes regularly under heating speed increasing by heightening of $\alpha -> \gamma $- transformation OR variant suppressed degree. Austenite crystals share with identical orientations (existed before quenching) enlarges when the heating rate are increasing and their formation at other variants are suppressed. When the critical rates ((1500-3000 K^{-1}$) are achieved then only one orientation of austenite crystals approximately arises as a result of limited suppress degree. Pseudomonocrystal austenite structure is formed when $\alpha -> \gamma $- transformation has been finished under these conditions (orientation restored effect).
Comparative investigations of the $\alpha -> \gamma $- transition crystallography has been carry out on preliminary tempering steel. There was analyzed the influence of the lath martensite structure different elements ($% \alpha $- crystals boundaries, retained austenite martensite dislocation substructure, carbide phase) on crystallographic features of austenite formation. On the base of comparative data has been made conclusion, that ''collective'' orientation behavior of the austenite crystal germs in the $% \alpha -> \gamma $- transformation are most sensitive to the changes in dislocation substructure of martensite. Hence, this one has fundamental importance for formation of the austenite crystallographically ordered structure. Retained austenite, martensite crystals boundaries (both have preserved by rapid heating to the beginning of $\alpha -> \gamma $- transformation) and carbide phase are not determinant in this austenite structure formation, although their definite affect on such one have been not excluded completely.
1. S.Prikhod'ko and R.Televich: Third European Powder Diffraction Conference EPDIC-3. -Vienna, Austria.