ВЛИЯНИЕ ХИМИЧЕСКОГО СОСТАВА И ТЕРМИЧЕСКОЙ ОБРАБОТКИ НА МЕХАНИЧЕСКИЕ СВОЙСТВА ПОКОВОК ПСЕВДО- β -ТИТАНОВОГО СПЛАВА

摘要

The article presents the results of statistical studies of mechanical properties of the deformed semi-finished products from Ti-10V-2Fe-3Al titanium alloy based on analysis of literature, experimental and commercial data, by the "Stadia 7" software package. The effect of reheat temperature for quenching T_h, as well as ageing temperature Т_(ag) on mechanical properties was evaluated by method of regressive analysis of the published te data. Equations for computing polymorphic transformation temperature beta-transus temperature β_(tr) and the quantity of primary α -phase, formed while quenching process on the temperatures interval from 700 ℃ to β_(tr) were obtained: β_(tr) = 890 + 22,3A1 - 13,9V - 8,0Fe, n_α =(0,3±0,02)·(β_(tr) - T_h), %. 1608 ingots and die forgings, manufactured by the industrial technology in 2007-2016 were also the subjects of research. All forgings were subjected to thermal treatment, consisted of quenching (763-798 ℃ for three hours followed by water cooling) and ageing (500-515 ℃ for 8 hours followed by air cooling). The following factors were selected for statistical analysis: alloying elements' and impurities' content, beta-transus temperature, alloy structural equivalents in aluminum [Al]_(equ)~(str) and molybdenum [Mo]_(equ)~(str), hardening temperature T_h and the aging temperature T _(ag), the mechanical properties (offset yield strength σ_(0,2), tensile strength σ_B, elongation δ, reduction of area Ψ, fracture toughness K_(1C)). Primary statistical processing and correlation-regression analysis were performed. Correlations between mechanical properties with deviations of the brand composition and heat treatment modes were established. At the first stage, pairwise correlations between the investigated factors were analyzed. The results of the analysis revealed that each element separately either does not affect, or affects weakly the level of mechanical properties of forgings, which is most likely stipulated by small intervals of their change. The joint action of the elements, which was evaluated by [Al]_(equ)~(str) and [Mo]_(equ)~(str), appeared to be more significant, the coefficient of multiple correlation was R = 0.3 ÷ 0.5, the fraction of the of the properties variation was γ =10÷25%. Coefficients of multiple property correlation with quenching temperature and aging temperature were equal to R = 0,3 ÷ 0,6 depending on the year of production. The joint effect on the properties of all four factors ([Al]_(equ)~(str), [Мо]_(equ)~(str), T_h, Т_(ag)) is evaluated by the coefficients R = 0,35 ÷ 0,67, γ =12÷45 %. The rest of the variation is stipulated by factors that could not be determined based on the data studied. The generalized regression dependence of the tensile strength of Ti-10-2-3 forgings on the chemical composition and heat treatment modes is: σ_B =1207 + (27,6±6,0)[Al]_(equ)~(str) + (24,1 ± 2,7)[Mo]_(equ)~(str) + +(1,6 ±0,17)T_h- (2,5 ±1,24)T_(ag).%Приведены результаты статистических исследований механических свойств деформированных полуфабрикатов титанового сплава Ti-10V-2Fe-3Al на основе анализа литературных, экспериментальных и производственных данных. Установлены корреляционные связи механических свойств с химическим составом и режимами упрочняющей термической обработки. Методом регрессионного анализа получены уравнения для расчёта температуры полиморфного превращения сплава, количества первичной α -фазы после закалки и предела прочности. Выявлено, что изменения марочного состава, температуры закалки и старения определяют 10-40 % колебаний механических свойств поковок. Остальной разброс обусловлен факторами, которые не удалось выявить на основе исследованных данных.