Solid State Phenomena Vol. 211

Abstract: Fast-developing such advanced industries as aviation, automotive and power-generation are increasing demand for new engineering materials which could resists such extreme operation conditions as high operating temperature, considerable stresses or operation in fume-affected environment. Highly desirable properties of such materials should include high hardness and strength, corrosion resistance (also when exposed to aggressive fumes) but also, first of all, low density. However such materials also requirements engineering methods to ensure obtain of good sound joints. Results in growing interest in modern engineering materials characterised by increasingly better operational parameters combined with a necessity to obtain joints of such materials representing good operation properties create important research and technological problems of today. These issues include also titanium joints or joints of titanium alloys based on intermetallic compounds. Brazing is one of the basic and sometimes even the only available welding method used for joining the aforesaid materials in production of various systems, heat exchangers and, in case of titanium alloys based on intermetallic compounds, turbine elements and space shuttle plating etc. This article presents the basic physical and chemical properties as well as the brazability of alloys based on intermetallic compounds. The work also describes the principle and mechanisms of diffusion-brazed joint formation as well as reveals the results of metallographic and strength tests involving diffusion-welded joints of TiAl48Cr2Nb2 casting alloy based on TiAl (γ) phase with the use of sandwich-type layers of silver-copper-titanium based filler metal (Ag-63%; Cu-35,5%; Ti-2%). Structural examination was performed by means of light microscopy. Furthermore, the article reveals the results of shear strength tests involving the aforementioned joints. Obtained mechanical test results of TiAl48Cr2Nb2 joints brazed with usage of three/different filler metal alloys ware compared.

Abstract: In this paper multivariant calculations of induction heating of titanium charge are presented. Calculation model consists of: hard coupled electromagnetic and thermal field analysis and weak coupled stress field analysis. A characteristic feature of titanium is low thermal conductivity. This causes problems with the heating of titanium charges, prolonging the heat treatment time. For this reason, it is preferred to use induction heating techniques, which allow to dissipate the power direct inside the heated charge volume. The side effect of intensified heating can be the appearance of harmful thermal stresses due to the large temperature gradients. Two series of simulations, in order to analyze the influence of the frequency and the supply power on the thermal stress and of the sample, was conducted.