Controlled Quenching of Aluminum Specimen in Flexible Spray Fields for the Reduction of Distortion

摘要

During heat treatment of age hardenable aluminum alloys, the resulting mechanical properties can particularly be influenced by the quenching process. To achieve a required strength, a high efficient cooling rate after solution annealing is necessary. In order to avoid distortion, a homogeneous distribution of quenching intensity should be realized as well. Controlled quenching within heat treatment processes of aluminum components can be realized by flexible jet and spray fields.Suitable heat transfer conditions of the aluminum components are realized by adjusted flexible flow fields (local and/or temporal) based on quenching simulations by Computational Fluid Dynamic methods (CFD). By the use of gas-(air), spray-(water/air) or jet-(water) flow fields, it is possible to adapt the quenching intensity to the component geometry, thereby controlling the mechanical properties as well as the distortion after heat treatment. The controlled quenching with aqueous media, especially the use of multiphase atomizers for spray cooling processes, offer the possibility for generating specific local heat transfer conditions and therefore achieving results of controlled asymmetric quenching on components to reduce distortion. For this purpose, a flexible spray field quenching process was integrated into the heat treatment for age hardening of different wrought-, cast-, and spray formed aluminum alloys.In this contribution, the process outline for spray quenching of aluminum specimen will be introduced. Results for aluminum specimen quenched in flexible spray fields will be discussed. The effect of quenching process parameters of the aqueous and air phase on the aluminum specimen will be determined through hardness measurements and tensile tests. Furthermore, the temperature profiles of asymmetrically quenched specimen through the usage of flexible nozzle fields will be discussed. Infrared thermography was performed on aluminum specimen to provide experimental data for the implementation of specific local heat transfer conditions into CFD heat transfer simulations to predict temperature profiles of the specimen, as they would appear in quenching processes.