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Structures and phases transitions of the alloys on the bases of Fe-Al intermetallic phases

Jabłońska M., Jasik A., Hanc A.

Archives of Materials Science and Engineering

2008

Vol. 29, nr 1

16-19

Purpose: The paper presents study the results of investigations the influence of the chemical composition and thermal treatment on the microstructures and phases transitions of intermetallics from the Fe-Al system. Design/methodology/approach: Investigated alloys with 28, 38 and 42% at. Al were melted in vacuum induction furnace. Next stage of the preparing was gravity casting for cylindrical graphite moulds in the form of bars. The structure was analyzed after annealing at 1000°C for 24 and 48 h. The phases transitions were carried out by using a DTA method on the Setsys made by Setaram. Findings: The microstructure observations indicated the presence of phases and precipitates in all investigated alloys. In all of the investigated alloys, precipitation of phases present in the structure as a result of the introduction of alloying additions, such as Zr, Cr, Mo and C, is visible. transformations connected with both disorder-order transitions and the initial temperature at which a liquid phase occurred in the alloys had taken place during heating. Research limitations/implications: The investigations showed that the very important in production of intermetallics from Fe-Al system is casting and thermal treatment process. The important is knowledge about the phases transformations in this alloys which taking the informations about the melting points, order – disorder transition and their correlations with structure and in consequence the mechanical properties. Practical implications: The formation of phases and precipitates during the heat treatment in these alloys have not been known until now. This structures aspects are significantly affect the properties of intermetallics from the Fe-Al system. In correlation with temperatures of phases transition they could take the most important informations for technological processing. Originality/value: We needed more details about intermetallic from Fe-Al system for their development. This paper are the valid supplement for development knowledge of the iron aluminides.

Some effects of phase transitions on heat propagation

Saxton K., Saxton R.

Archives of Mechanics

2002

Vol. 54, nr 5-6

635-646

We consider phase transitions in solids due to heat propagating through crystalline materials at low temperatures. These are considered in a steady state context where, at the transition temperature, the specific heat becomes singular and the heat conductivity has a maximum. Several consequences are found for the heat capacity having finite or infinite jump discontinuities.