EFFECT OF HEATING TEMPERATURE OF THE BILLET BEFORE WARM ROLLING ON THE MICROSTRUCTURE AND PROPERTIES OF VT22 TITANIUM ALLOY

10.25712/ASTU.1811-1416.2024.02.008

Abstract

Complex-alloyed VT22 titanium alloy is a high-strength alloy to made critical aerospace products. This alloy is usually used in a coarse-grained state, and the problems are low technological plasticity and high instability of mechanical properties of the material in products. These problems are most apparent in the manufacture of thin-walled hollow-core construction, which can be successfully produced by superplastic forming from sheet blanks with a fine- or ultrafine-grained (UFG) microstructure. The UFG microstructure in sheet blanks of VT22 alloy can be obtained as a result of isothermal rolling. However, isothermal rolling significantly increases the cost of production, making it economically unprofitable. In this regard, we investigated the possibility of producing UFG sheets of titanium alloy VT22 by warm rolling on cold rollers at the temperature range of 600-750 °C. The results of the studies show that sheet rolling of billets heated to a temperature of 600 °С makes it possible to obtain a UFG state in VT22 titanium alloy with grain-subgrain microstructure parameters of less than 300 nm. The microhardness of the obtained sheet blanks is 20 % higher compared to the coarse-grained VT22 alloy. Grain elongation along the rolling plane decreases as the heating temperature of the workpieces prior to rolling is reduced in the temperature range studied. Such results can be particularly useful in optimizing the conditions for obtaining thin sheets with UFG or nanocrystalline structure.