Application of the Entropy Approach for Analyzing the D16 Alloy Aging Stages
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INUM ALLOYS UDC 621.785.78:669.715
APPLICATION OF THE ENTROPY APPROACH FOR ANALYZING THE D16 ALLOY AGING STAGES E. A. Nosova1 Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 22 – 26, June, 2020.
The possibility of evaluating the structural entropy of sheet samples of D16 alloy after aging at 50, 100, 150, and 200°C for 15, 30, 60, 120, and 240 min is considered. A quantitative relationship between the treatment conditions and crystallinity level is established. The effect of the stages of structural changes during aging on the variation of structural entropy is determined.
Key words: aluminum alloy, aging, stress-strain curve, structural entropy, properties.
verings would require processing of large amounts of structure- and property-related data. In study [5], an assumption was made about the effect of the phase distribution patterns after aging of D16 alloy on its stamping ability. In this case, performing calculations to evaluate the homogeneity of the disperse phase distribution becomes possible only after the phase aging stage is completed. During the stage of zonal aging, more complex finestructure observations are required [3]. In addition, the phase composition of aged aluminum alloys depends on the treatment conditions, such as temperature and duration of aging, and application of external mechanical load [6]. Such conditions can affect the resulting alloy properties, as well as failure mode of the products and their service life [4]. Therefore, knowing the aging stages in case of a certain combination of the treatment conditions will help achieve the desired properties. Structural changes during deformation and heat treatment of D16 alloy may affect the level of structural entropy. For example, cold-rolled metal alloy sheets subjected to high-reduction ratios, or castings obtained by directional crystallization are characterized by a preferential crystallographic texture and, hence, exhibit a high degree of alignment of crystallographic planes, and demonstrate a strongly-pronounced anisotropy of properties (mechanical, physical, and technological) [7 – 9]. Monograph [10] offers a procedure for calculating the structural entropy based on the results of analysis of the
INTRODUCTION Alloy D16 is commonly used in aeronautical engineering as a material for manufacturing aircraft bodies. The mechanical and technological properties of this alloy sheets vary significantly depending on the heat treatment conditions, which may affect the quality of the resulting products, as well as specifics of the sheet stamping process design (number of passes, maximum degree of deformation per pass, operating force, etc.). Studying structural changes in the D16 alloy during aging is of interest to many researchers, as it enables a wide range of properties [1 – 3]. Selecting the most favorable condition of the sheet stock suitable for subsequent treatment and manufacturing of a stamped product depends on the aging stage, which occurs at a certain moment of time [2]. During the aging process, heat
