Forecasting of mechanical properties of VТ6 and VТ3-1 titanium alloys forgings depending on chemical composition and structure

Abstract

The paper studies the statistical dependence of the mechanical properties of 218 forgings (15 types) made of VT3-1 and VT6 alloys in 2000–2014 on chemical composition (the content of alloying elements and admixtures, structural and strength equivalents of aluminum and molybdenum), structure types, subtypes and parameters after annealing, quenching and aging. It was found that the strength and plastic properties of one-type forgings vary quite widely. The share of variation of forging properties due to fluctuations in the content of main components and admixtures, as well as the influence of structure types and sizes of structural components was estimated. Based on the correlation analysis it was revealed that the change of each alloying element or admixture content has a little or no effect on forging properties. This is caused by small increments of their change within the grade composition. However, their total content expressed in terms of aluminum and molybdenum equivalents can vary over a fairly wide range. It was statistically substantiated that the share of tensile strength variation of VT3-1 and VT6 forgings may be ~25÷65 % due to the influence of their chemical compositions (in terms of aluminum and molybdenum equivalents), and about 20 % due to only the influence of structure types and subtypes. When these two factors (composition + structure) are combined, the share of variation can reach ~50÷65 %. For plastic properties and impact toughness, this figure is less and ranges from 20 to 35 %. The mathematical models are offered to forecast the mechanical properties of forgings depending on the structure parameters and aluminum and molybdenum equivalents.