Deformační chování a strukturotvorné procesy při tváření vybraných aluminidů železa

Abstract

Iron aluminides (type Fe3Al) were tested with following additives: with TiB2, with Ti, with B, with Ti and B, their chemical compositions in wt. % as follow: IM1 (Fe - 16.5Al - 3.96Cr - 0.33TiB2 - 0.01C), IM2 (Fe - 19.2Al - 4.89Cr - 0.68Ti - 0.04C), IM3 (Fe - 16.8Al - 4.00Cr - 0.063B - 0.02C), IM4 (Fe - 18.4Al - 4.94Cr - 0.61Ti - 0.070B - 0.04C) and alloy Fe9Al4Cr0,5Zr. Flat specimens with graded in size thickness were hot rolled. An advantage of the sample with thickness graded in size consists in a three times higher quantity of data achieved by its rolling at exactly defined temperature as compared with rolling of one flat sample with a constant thickness. For each sample the following parameters were changed: temperature, roll gap adjustment (i.e. total deformation of the particular step of the sample) and nominal revolutions of rolls – they determine the achieved strain rate. Deformation resistance was calculated, by method based on non-linear regression by means of the statistical software Unistat 5.5, from the roll force values that were measured in the laboratory rolling mill Tandem. Mathematical models of mean flow stress of selected iron aluminides depending on temperature and strain were developed. Postdynamic structure-forming processes of the tested aluminides were investigated by metallography after hot rolling in the laboratory mill stand K350. Several rolling and cooling modes were used, and then the structures of each iron aluminides were compared. Differences in deformation behavior and formability of the materials, which creep resistance at high temperatures is good, were described.