Mechanism-based understanding of functional grading focused on fatigue behaviour of additively processed Ti-6Al-4V and Al-12Si alloys

• Applicants: Professor Dr. Claus Emmelmann; Professor Dr.-Ing. Frank Walther
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 336368661

Major objective of the project is to harness the potential of the selective laser melting (SLM) process to obtain localized part properties, within a range of few hundred microns, which are favorable for the fatigue performance of a SLM-manufactured component. Fatigue performance of SLM parts have been reported to be low as compared to conventionally manufactured alloys. Overcoming the issues causing reduction of fatigue strength can be very expensive if the manufacturing of the whole component is oriented for fatigue performance. However, after pre-analysis of the designed geometry, critical locations for fatigue can be identified in terms of stress concentrations. These critical locations then need to be manufactured in a way that they are fatigue-tolerant. It will achieve the higher performance with a marginal increase in manufacturing costs. The expected success in manufacturing functionally-graded structures will be helpful for industry for manufacturing reliable components. To obtain these objectives, there are several factors, the influence of which as well as their interaction needs to be understood. Therefore, process-structure-property relationships will be developed making use of process parameters, metallography and microscopy as well as mechanical property investigations. Such mechanism-based relationship will be the basis for manufacturing real structural components which have locally optimized properties. For this purpose, optimal process parameters for re-melting will be determined which significantly affect internal defects responsible for fatigue scatter. After that, optimal depth of re-melting will be investigated such that the resulting re-melting process remains cost-efficient. Also the pre-heating temperature effective in elimination of large pores as well as its influence on thermal gradients responsible for varying microstructures is an important objective of the project. Lastly, a detailed understanding of graded microstructures and the interaction between different microstructures regarding deformation and damage mechanisms will be determined.

• DFG Programme: Research Grants