Abstract
Age hardening aluminium alloys obtain their strength by forming precipitates. This precipitation-hardened state is often the initial condition for short-term heat treatments, like welding processes or local laser heat treatment to produce tailored heat-treated profiles (THTP). During these heat treatments, the strength-increasing precipitates are dissolved depending on the maximum temperature and the material is softened in these areas. Depending on the temperature path, the mechanical properties differ between heating and cooling at the same temperature. To model this behavior, a phenomenological material model was developed based on the dissolution characteristics and experimental flow curves were developed depending on the current temperature and the maximum temperature. The dissolution characteristics were analyzed by calorimetry. The mechanical properties at different temperatures and peak temperatures were recorded by thermomechanical analysis. The usual phase transformation equations in the Finite Element Method (FEM) code, which were developed for phase transformation in steels, were used to develop a phenomenological model for the mechanical properties as a function of the relevant heat treatment parameters. This material model was implemented for aluminium alloy 6060 T4 in the finite element software LS-DYNA (Livermore Software Technology Corporation).
Highlights
Heat treatments are used to influence the mechanical properties of metallic materials
We developed a phenomenological mechanical material model for precipitation hardening aluminium alloys, which can describe flow curves as a function of the actual temperature and the peak temperature of the heat treatment
The flow curves clearly show that our phenomenological mechanical material model for precipitation hardening aluminium alloys agrees very well with the experiments
Summary
Heat treatments are used to influence the mechanical properties of metallic materials. Heat treatment simulation of the short-time heat treatments used for tailored heat-treating blanks (THTB) [13,14] and profiles (THTP) for aluminium has not yet been performed These short-term heat treatments, which locally heat material areas using a laser, are characterized by very high heating rates of several 100 Ks−1 , almost no soaking at peak temperature and subsequent cooling at a few 10 Ks−1. Material models were developed for producing tailored heat-treated semi-finished products [13,14] These material models were developed for forming simulations and provide the mechanical properties at room temperature depending on the maximum temperature during heat treatment. Empirical-phenomenological model approaches provide simple descriptions of the material behavior as a function of the process parameters
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