Influence of Heat Treatment Modes on the Structure and Properties of Large-Sized Products of Advanced Aviation Equipment Made of Alloys of the Al-Zn-Mg-Cu System

Abstract

Introduction. High-strength aluminum-based alloys of the Al-Zn-Mg-Cu alloying system are commonly used in aircraft manufacturing. However, there is a need to address the issue of achieving the desired level of mechanical properties in large-scale parts made from these alloys during heat treatment. Additionally, studies on the evaluation of corrosion resistance during heat treatment are also essential. The aim of this work was to determine the modes of heat treatment to achieve the necessary values of mechanical properties and resistance to corrosion cracking of parts made of large-sized deformed blanks of alloys of the Al-Zn-Mg-Cu alloying system.Materials and Methods. The research was conducted on parts made from forged 1933 alloy forgings and B93pch stamped blanks. The influence of heat treatment on the mechanical properties (strength, ductility, hardness) and microstructure, as well as electrical conductivity, was determined. Tensile tests were carried out both on samples subjected to heat treatment after cutting from forgings and stamped blanks, and on samples cut from massive templets that were heat treated together with the products. Electrical conductivity allowed us to assess the level of solid solution supersaturation and predict resistance to corrosion cracking.Results. The results of the study showed the necessity of a differentiated approach to assigning the duration of aging stages, depending on the alloy grade, configuration, and dimensions of the products, as well as the requirements for the level of properties. Variants and modes of heat treatment were proposed for products made from alloys 1933 and B93pch, providing the necessary level of mechanical properties and resistance to corrosion cracking.Discussion and Conclusion. Cases of inconsistency in strength properties in the longitudinal and transverse (in width) directions of the fiber of parts made from large-sized blanks of alloys 1933 and B93pch have been established. Modes and options for heat treatment of parts were proposed, allowing the achievement of the required values of mechanical properties and corrosion resistance. This provides for a halving of the aging time for alloy 1933 or an increase of 25% for alloy B95pch.