Unique Microstructure established by the combination of Additive Manufacturing and Equal Channel Angular Pressing

• Applicant: Professor Dr.-Ing. Thomas Niendorf, since 4/2024
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 534655509

The exceptional strength-to-density ratio of Aluminum (Al) alloys offers a great potential for reducing the weights of components. In order to broaden the applications of these alloys and replace high-strength steels with them, various techniques can be employed to enhance the strength of Al alloys. The rapid manufacturing of Al alloys provides a great potential for a systematic design of microstructure and consequently the improvement of mechanical properties. AlSi12 alloy fabricated via laser powder bed fusion (L-PBF) shows a coarse-grained Al matrix consisting of fine Si networks with higher strength in comparison to the conventionally casted parts. A unique microstructure with exceptional mechanical properties can be achieved by severe plastic (SPD) deformation. However, coarsening and agglomeration of Si networks due to the high processing temperature during some SPD techniques such as friction stir processing and friction stir welding may adversely affect the strength of these alloys. The very first study on the effect of equal channel angular extrusion/pressing (ECAE/P) on the mechanical properties and microstructure of additively manufactured Al alloys reveals that this SPD method is capable of enhancing both strength and ductility of these alloys. Due to the low ECAP processing temperature, the Si-cells only get stretched during ECAP, they are not dissolved. The UFG microstructure only forms within the cells. Thus, a unique heterostructure is finally formed. The analysis of the current state-of-the-art verifies that there are no systematic investigations on the influence of ECAP on the microstructural evolutions and mechanical properties of Al alloys fabricated via additive manufacturing (AM). Therefore, the primary motivation of the present proposal is to complement the in-depth understanding of the impact of ECAP as a post-processing treatment on the microstructure and mechanical behavior of L-PBF Al alloys. A reference as-cast alloy will be investigated in order to explore the impact of the initial microstructure (i.e. AM microstructure versus as-cast counterpart) on the mechanical properties, especially the cyclic deformation behavior and final microstructure of the alloys. The application could gain relevance and connectivity if the Si content would be increased to a level exceeding the eutectic phase. This may also lead to the acquisition of more knowledge in the field of additive manufacturing in the present proposal. In this regard, hypereutectic Al-Si alloys (AlSi20 and AlSi50) will be fabricated employing LB-PBF. Then, ECAP up to 4 passes will also be carried out on hypereutectic Al-Si alloys.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Seyedvahid Sajjadifar, until 4/2024