Dilatometric Analysis and Kinetics Research of Martensitic Transformation under a Temperature Gradient and Stress

Based on material constitutive models and the classic Koistinen–Marburger (KM) kinetics model, a new dilatometric analysis model was developed to extract the kinetics curve of martensitic transformation under a temperature gradient and stress from the measured dilatometric data and to determine the transformation parameters. The proposed dilatometric analysis model is generally for athermal martensitic transformation, relying only on the average atom volume of martensite and austenite. Furthermore, through theoretical calculations, the proposed model also provided a more accurate method for obtaining the martensite start temperature, which is different from the traditional method. According to the dilatometric analysis results for the martensitic transformation of a type of high-strength low-alloy steel, and the thermodynamic basis of martensitic transformation, a refined kinetics model was developed that successfully predicted the martensitic transformation kinetics curves under different stresses, taking into account the physical significance of the transformation parameter α and the driving force of stress for martensitic transformation.

RESEARCH OF THE PROCESS OF OBTAINING INTERESTERIFIED FAT FOR MARGARINE PRODUCTION ON THE BASIS OF SUNFLOWER OIL AND PALM STEARIN

The study presents the results of transesterification of a mixture of sunflower oil and palm stearin in various proportions and dilatometric analysis of the obtained transesterifications was carried out. For example, the ratios in the mixture of sunflower oil and palm stearin 15/85, 25/75, 30/70, 50/50 were subjected to transesterification in the laboratory, and the transesterifications used for the spread and margarine were obtained, and the optimal mixture ratios were determined. By dilatometric analysis, it was found that it is possible to obtain interesterificates in the ratio of a mixture of sunflower oil and palm stearin at 50/50 for a good spreading and high plasticity spread (t = 31 ℃), at 30/70 for margarine providing porosity for baking (t = 39 ℃) , at 25/75 to margarine used for puff pastry (t = 43 ℃). In addition, the fatty acid content of sunflower oil and palm stearin used in the experiments was also determined.

Researches in the field of composite HCBS and of the refractory materials on their base in the Al2O3‒SiO2‒SiC system. Part 3

The rheological properties are described both for the initial (basic) HCBS of the composite bauxite and the same HCBS with 15 % SiC, as well as with the addition of 1 and 2 % of Si. The influence of the metal silicon addition was investigated, which decreased the sintering temperature and promoted the sealed porosity formation. It was established that in the materials containing Si addition, between the burning temperature of 1300‒1400 °C under the open porosity decreasing from 2,7 to 1,6 % the oxidation of SiC or Si can be slackened or inhibited. The dilatometric analysis showed that during the non-isothermal heating of the samples containing 10‒30 % of SiC, the certain degree of SiC oxidation can be noticed and the mullitization of the material became slower. Ill.7. Ref. 20. Tab. 1.