Group Leader

Key Publications

Zahra Tarzimoghadam, Dirk Ponge, Jutta Klöwer, and Dierk Raabe, "Hydrogen-assisted failure in Ni-based superalloy 718 studied under in situ hydrogen charging: The role of localized deformation in crack propagation," Acta Materialia 128, 365-374 (2017).
Motomichi Koyama, Zhao Zhang, Meimei Wang, Dirk Ponge, Dierk Raabe, Kaneaki Tsuzaki, Hiroshi Noguchi, and Cemal Cem Tasan, "Bone-like crack resistance in hierarchical metastable nanolaminate steels," Science 355 (6329), 1055-1057 (2017).
Huan Zhao, Frédéric De Geuser, Alisson Kwiatkowski da Silva, Agnieszka Szczepaniak, Baptiste Gault, Dirk Ponge, and Dierk Raabe, "Segregation assisted grain boundary precipitation in a model Al–Zn–Mg–Cu alloy," Acta Materialia 156, 318-329 (2018).
Minjie Lai, Yujiao Li, L. Lillpopp, Dirk Ponge, S. Will, and Dierk Raabe, "On the origin of the improvement of shape memory effect by precipitating VC in Fe–Mn–Si-based shape memory alloys," Acta Materialia 155, 222-235 (2018).
Alisson Kwiatkowski da Silva, Dirk Ponge, Zirong Peng, Gerhard Inden, Y. Lu, Andrew J. Breen, Baptiste Gault, and Dierk Raabe, "Phase nucleation through confined spinodal fluctuations at crystal defects evidenced in Fe–Mn alloys," Nature Communications 9 (1), 1137 (2018).
Mengji Yao, Emanuel David Welsch, Dirk Ponge, Seyed Masood Hafez Haghighat, Stefanie Sandlöbes, Pyuck-Pa Choi, Michael Herbig, Ivan Bleskov, Tilmann Hickel, Marta Lipinska-Chwalek, Pratheek Shanthraj, Christina Scheu, Stefan Zaefferer, Baptiste Gault, and Dierk Raabe, "Strengthening and strain hardening mechanisms in a precipitation-hardened high-Mn lightweight steel," Acta Materialia 140, 258-273 (2017).

Mechanism-based Alloy Design

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Mechanism-based Alloy Design

The group ‘Mechanism-based Alloy Design’ works on the microstructure-oriented design of advanced high strength steels, high entropy alloys as well as on engineering Al-, Ni- and Ti-alloys [1-10].
Fig. 1: Hardness distribution in thermomechanically treated DP steel in front of the interfaces. Zoom Image
Fig. 1: Hardness distribution in thermomechanically treated DP steel in front of the interfaces.

Projects focus on multiple strain hardening mechanisms such as the interplay of dislocations, twins and deformation driven phase transformations. Of special interest are confined phase transformation phenomena at grain boundaries and dislocations. Especially for materials with high strength, hydrogen embrittlement provides a challenge. Here the damage and failure mechanisms are analyzed in order to develop novel high strength materials with low susceptibility against hydrogen embrittlement. Projects in the group make intense use of the processing, mechanical testing and microstructure characterization facilities at MPIE down to the atomic scale. Projects are pursued in collaboration with partners from modelling, APT and microscopy. Theory-guided thermomechanical processing is a main pathway for optimizing the microstructures and mechanical properties of complex alloys. In this context a main objective of projects in this group lies in understanding and utilizing elemental and mechanical partitioning effects among neighboring phases on the one hand and among the matrix and lattice defects on the other hand with the aim to adjust the (meta-) stability of local phase states. Depending on phase stability, deformation driven athermal transformations can be triggered such as spatially confined transformation-induced plasticity (TRIP) and transformation-inducted twinning (TWIP). Main examples are the design of ultrafine grained, partially metastable, maraging, multiphase, medium-Manganese, martensite-to-austenite reversion and weight reduced steels for automotive, manufacturing and infrastructure applications.

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