Forecasting Mechanical Properties of Forgings of VT6 and VT3-1 Titanium Alloys Depending on the Chemical Composition and Structure

Abstract

The statistical dependences of the mechanical properties of 218 forgings (15 dimension types) made of VT3-1 and VT6 alloys in 2000–2014 on the chemical composition (content of alloying elements and impurities and structural and strength aluminum and molybdenum equivalents), type, subtype, and structural parameters after annealing, quenching, and aging are investigated. It is established that the strength and plastic properties of single-type forgings vary rather widely. The part of the variation in the forging properties caused by fluctuations of the content of major components and impurities, as well as by the influence of the structural type and sizes of structural components, is evaluated. It is revealed based on correlation analysis that the variation in amounts of each alloying element and impurity has little or no effect on the forging properties. This is caused by small fluctuation intervals of their concentrations in the limits of the grade composition. However, their total content expressed through aluminum and molybdenum equivalents can vary in a rather wide range. It is statistically substantiated that the part of the variation in the tensile strength of forgings of VT3-1 and VT6 alloys caused by the influence of the chemical composition (recalculated to aluminum and molybdenum equivalents) may be ∼25–65%, while that caused by the influence of the structural type and subtype is about 20%. The part of the variation under the joint effect of these two factors (composition + structure) can reach ∼50–65%. This index for plasticity and impact toughness is smaller and lies in a range of 20–35%. Mathematical models for forecasting the mechanical properties of forgings depending on the structural parameters and aluminum and molybdenum equivalents are proposed.