An accurate empirical formula for determining the density of heat-resistant nickel alloys

Abstract

The density of a substance is one of its main physical characteristics. This is especially true for materials used in aviation, where the mass of each structural element should be minimized as much as possible. When developing new structural materials, for example, heat-resistant nickel alloys, which are widely used in the manufacture of gas turbine engine parts, it is extremely important to have a reliable and accurate method for assessing the density of the material being developed. Until now, no unified method has been proposed for calculating the density of heat-resistant nickel alloys. The paper reviews the available approaches to assessing the density of alloys and proposes a new formula that allows one to calculate the density of an alloy with a high accuracy based on the information on its composition. The proposed approach takes into account the spatial fcc structure of heat-resistant nickel alloys as well as the molar mass and molar volume of the elements that form the alloy. To check the accuracy of the calculations, a database of 69 heat-resistant nickel alloys was collected, containing information on the composition of the alloys and their known density. According to the proposed formula, as well as using some other known approaches, the density for the alloys from the database was calculated. The calculation results showed that the proposed method provided the best accuracy among all considered ones: the standard deviation of the calculated values from the real ones for the entire sample was 0.1%, the mean values and medians practically coincide. In addition, the calculation errors are normally distributed and have an average value of −0.0001. The existing methods give a minimum error of 1.2%, thus, the proposed approach improved the accuracy of calculating the density of heat-resistant nickel alloys by about an order of magnitude, which is a significant result both from the point of view of the general scientific approach and from the point of view of engineering practice. Taking into account the results obtained, the proposed formula can be widely used in the development of new and modification of existing heat-resistant nickel alloys. © 2021, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.