The Use of Acoustic Emission and Neural Network in the Study of Phase Transformation below MS

Acoustic emission and dilatometry were applied to investigate the characteristics of phase transformations in bearing steel 100CrMnSi6-4 during austempering below the martensite start temperature (MS 175 °C) at 150 °C. The aim of this study is to characterize the product of transformation occurring below the MS temperature using various research methods. Analysis of the dilatometric curves shows that, after the formation of athermal martensite below the MS temperature, the austenite continues to undergo isothermal transformation, indicating the formation of bainite. Additionally, tests were carried out with the use of acoustic emission during isothermal hardening of the adopted steel. The obtained acoustic emission signals were analyzed using an artificial neural network. The results, in the form of a graph of the frequency of acoustic emission (AE) event occurrence as a function of time, make it possible to infer about the bainite isothermal transformation. The results of this research may be used in the future to design optimal heat treatment methods and, consequently, may enable desired microstructure shaping.

High-Copper Cast Irons for the Products of Tribotechnical Applied

The paper presents the results of the development of a special group of cast composite materials based on nodular cast irons. The alloys were based on alloying cast iron with copper in amounts that exceed its solubility in liquid Fe-C-Si systems (Cu>6 wt.%). A new component is obtained in the structure of castings in the form of a complex mixture based on the Cu-phase. Inclusions are relatively large (up to 200 μm) and globular in shape, with a uniform allocation in the volume of the castings. This favorably distinguishes the obtained alloys from the known cast irons and gives them high antifriction properties. With isothermal hardening, it is possible to obtain the lowest values of wear for structures of lower bainite. Developed cast composite materials are recommended to be used as tribotechnical materials working in conditions of poor lubrication and corrosion.

Highly-Dispersed Wollastonite-Based Additive and its Effect on Fine Concrete Strength

The effective highly-dispersed additive on the basis of the natural mineral wollastonite has been developed and studied. It enables obtaining fine concrete with the bending strength of up to 21.6 MPa and the strength of compression of up to 55 MPa, and the content of 0.5% (in terms of dry matter). The additive is a suspension of wollastonite after mechanical, and then ultrasonic processing in the aquatic environment of the anionic stabilizer of naphthalene-formaldehyde type. Due to the laser granulometry it has been ascertained that grinding wollastonite together with the anionic stabilizer leads to a change in the specific surface from 20 400 to 32 600 cm2/cm3 and to forming the particles with a modal diameter of 10.31 μm. After ultrasonic processing in the aquatic stabilizer environment the wollastonite particle size reduces to 0.4 μm. The positive heat and humidity effect on the structure and strength of the concrete with highly-dispersed wollastonite-based additive under the mode 3+4+3 h at the isothermal hardening temperature of 80оС is shown. The application of the developed additive in the fine concrete composition makes it possible to save up to 15% of cement due to the strength increase.