Influence of High-Temperature Annealing of Aluminum Alloys AMg6 and V95 on Their Structural-Phase State and Strength Properties

Abstract

The widespread use of structural aluminum alloys AMg6 and V95 in modern mechanical engineering has led to the identification of such a problem as the non-optimal structure of commercial semi-finished products from these alloys. Traditional types of heat treatment do not always make it possible to correct the structure and obtain a high complex of operational properties. The most common structural defects in commercial semi-finished aluminum alloys containing magnesium and zinc are banding formed by the strengthening intermetallic phase MgZn₂. The structure of magnesium–aluminum alloys has been studied by high-resolution optical microscopy under various heat treatment modes, which include long-term homogenization annealing. The studies were carried out on samples of AMg6 and V95 alloys. For heat treatment, a chamber furnace of the SNOL type equipped with a PID controller was used; the samples were loaded into a furnace preheated to a temperature of 500°C and kept in it for 8 and 16 h. After the exposure was completed, the samples were removed from the furnace and cooled in still air. The hardness was measured on the original samples, samples after heat treatment and 14 days after heat treatment. Studies have shown that an increase in the time of high-temperature holding at 500°C for both alloys leads to the dissolution of intermetallic particles. As a result of the ongoing structural-phase transformations during further cooling and subsequent natural aging, the intermetallic phase again precipitates from the solid solution, as shown by hardness measurements made on the original samples, then after high-temperature annealing and subsequently after natural aging for 14 days.