DETERMINATION OF POLYMORPHIC TRANSFORMATION TEMPERATURE FOR ALLOY VT8 AND PROPERTIES OF STRUCTURE AFTER HARDENING WITH DIFFERENT TEMPERATURES
DOI:
https://doi.org/10.14529/met180206Keywords:
двухфазные титановые сплавы, ВТ8, температура полиморфного превращения, закалка, структура закаленных титановых сплавов, микротвердостьAbstract
The temperature of polymorphic transformation (Tpt) has been determined for accurate composition of two-phase titanium alloy which has been marked like VT8 through different ways, specifically: the method of trial quench and with the help of dilatometric and differential thermal methods of analysis. The values of Tpt (approximately 1027 °С) have been obtained by the listed methods of analysis practically do not depend on the used method of determination. Herewith the phase composition has been estimated qualitatively and quantitatively for the hardened samples of alloy VT8 using optical and scanning electron microscopes and the chemical composition with the help of the micro X-ray spectral analysis. The influence of the quenching temperature on the hardness has been investigated. Also, the hardness of the individual structural components and alloy VT8 as a whole unit has been measured. Hardness curves are based depending of the quenching temperature; the results are displayed in tabular and graphical form.
The coefficient k (for the formula) has been found for the calculation of allotropic transformation temperature for this alloy using the known temperature of hardening and quantity of preserved α-phase of hardened structure. The album of the microstructures after quench with different temperatures has been created, this album will allow to reduce the duration of preliminary works for finding specific temperature of polymorphic transformation in production conditions for each new batch of alloy VT8 with another chemical composition (but within the vintage). Knowledge of which is necessary for setting the temperature regime of treatment, which eliminates overheating.
The possibilities of the methods for finding temperature of the polymorphic transformation (Tpt) for the titanium diphase VT8 alloy, including in the production conditions, have been estimated.
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