Tailor Alloyed Blanks - Manufacturing of high-strength process-adapted semi-finished parts by a local laser-based adaption of the alloying system

• Applicants: Professorin Dr.-Ing. Marion Merklein; Professor Dr.-Ing. Michael Schmidt
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 521490180

The aim of this research project is the development of a fundamental process understanding for the enhancement of the forming limits of 7XXX aluminum alloys by localized adaptation of the alloy by means of laser-based manufacturing processes. In this context, the combination of laser-induced element vaporization in the first step and laser wire alloying as a second process step is aimed to achieve a local adaptation of the alloy composition and the microstructure across the entire depth of the semi-finished product. It is intended to locally adapt the chemical composition of the 7XXX alloy to a 6XXX alloy because this type of alloy has superior forming properties coupled with a lower tendency to undergo artificial aging at low temperatures. During welding, aluminum alloys tend to have a high tendency to heat cracking. Because the high Zn content in combination with Mg in alloys of the 7XXX series primarily leads to lower formability in hot or cold aged conditions than in less solid grades, the concentration of the elements must be reduced locally in the first subprocess by remelting and selective evaporation. More specifically, the aim is to reduce the Zn concentration from approx. 5 - 6 wt.% to a content of approx. 0.2 - 0.5-wt.%. In the subsequent laser wire alloying process, the Zn- and Mg-depleted material area is alloyed with a Si-containing wire material. The aim is to increase the Si content to 0. 5- to 0.7-wt% maximum, thus resulting in a chemical composition similar to a 6XXX alloy in the modified material volume. The approach represents a significant innovation compared with the current state of research, which has so far been restricted exclusively by extending the forming limits of high-strength aluminum alloys using warm or hot forming operations or local heat treatment before the forming process. A prerequisite for a successful local alloy adaptation is the fundamental investigation of interactions during element evaporation of low-evaporation alloying elements. In addition, the integration of additional elements in laser-based wire alloying influences the microstructure and mechanical properties. In addition, the finishing of the modified material area in a rolling process to smooth the weld area, as well as investigations into the forming behavior of modified blanks by means of 3-point bending tests, are a further focus of the project.

• DFG Programme: Research Grants