D. Ponge

Max Planck Institute for Sustainable Materials | MPIE · Department of Microstructure Physics and Alloy Design

In situ microscopic-digital image correlation (µ-DIC) is used to investigate the strain partitioning and strain localization behavior in a medium manganese steel. Continuous yielding results from strain partitioning with higher strain in the reverted austenite (γR) islands and less strain in the tempered martensite matrix, both in hot and cold roll...

The antagonism between strength and resistance to hydrogen embrittlement in metallic materials is an intrinsic obstacle to the design of lightweight yet reliable structural components operated in hydrogen-containing environments. Economical and scalable microstructural solutions to this challenge must be found. Here, we introduce a counterintuitive...

While age-hardened austenitic high-Mn and high-Al lightweight steels exhibit excellent strength-ductility combinations, their properties are strongly degraded when mechanically loaded under harsh environments, e.g. with the presence of hydrogen (H). The H embrittlement in this type of materials, especially pertaining to the effect of κ-carbide prec...

Steels with medium manganese (Mn) content (3∼12 wt-%) have emerged as a new alloy class and received considerable attention during the last decade. The microstructure and mechanical response of such alloys show significant differences from those of established steel grades, especially pertaining to the microstructural variety that can be tuned and...

The precipitation of grain boundary (GB) κ-carbides critically influences the damage-tolerance ability of high-Mn high-Al lightweight steels, particularly in harsh environments (cryogenic and H environments). The formation and growth behavior of these carbides thus need to be understood. In this work, we use atom probe tomography and four-dimension...

Entropy-related phase stabilization can allow compositionally complex solid solutions of multiple principal elements. The massive mixing approach was originally introduced for metals and has recently been extended to ionic, semiconductor, polymer and low-dimensional materials. Multielement mixing can leverage new types of random, weakly ordered clu...

Ironmaking is one of the largest single causes of global warming. The reduction of iron ores with fossil fuel currently generates about 7% of the global carbon dioxide emissions for producing 1.85 billion tons of steel per year. This fact leads to an urgent decarbonization challenge in the steel industry and fuels efforts to deploy renewable and ca...

The interaction between boron and hydrogen at grain boundaries has been investigated experimentally and numerically in boron-doped and boron-free martensitic steels using thermal desorption spectrometry (TDS) and ab initio calculations. The calculations show that boron, which mostly segregates into prior austenite grain boundaries (PAGBs), repels h...

Circular Steel for Fast Decarbonization: Thermodynamics, Kinetics, and Microstructure Behind Upcycling Scrap into High-Performance Sheet Steel: Steel production stands accounts for approximatelybout 8% of all global CO2 emissions, with the primary steelmaking route from using iron ores accounting for about 80% of those emissions, mainly due to the...

Steel production accounts for approximately 8% of all global CO 2 emissions, with the primary steelmaking route using iron ores accounting for about 80% of those emissions, mainly due to the use of fossil-based reductants and fuel. Hydrogen-based reduction of iron oxide is an alternative for primary synthesis. However, to counteract global warming,...

The degradation of mechanical properties caused by grain coarsening or the formation of brittle phases during welding reduces the longevity of products. Here, we report advances in the weld quality of ultra-high strength steels by utilizing Nb and Cr instead of Ni. Sole addition of Cr, as an alternative to Ni, has limitations in developing fine wel...

Aluminum alloys play an important role in circular metallurgy due to their good recyclability and 95% energy gain when made from scrap. Their low density and high strength translate linearly to lower greenhouse gas emissions in transportation, and their excellent corrosion resistance enhances product longevity. The durability of Al alloys stems fro...

Wind turbine gearbox (WTGB) bearings suffer from premature failures through white etching cracks (WECs). To investigate causes of this failure mechanism, we tested two types of 100Cr6 bearing steel components. We carried out rolling contact fatigue experiments on standard washers and material extracted from a WTGB bearing. These differed strongly i...

The mechanical properties of metallic materials often significantly deteriorate when used under harsh conditions, particularly at cryogenic temperatures. Yet, safe and lasting low-temperature infrastructures are needed to realize the growing global demand for liquid energy carriers such as hydrogen[1]. Traditional microstructure strategies designed...

Iron making is the biggest single cause of global warming. The reduction of iron ores with carbon generates about 7% of the global carbon dioxide emissions to produce ≈1.85 billion tons of steel per year. This dramatic scenario fuels efforts to re-invent this sector by using renewable and carbon-free reductants and electricity. Here, the authors sh...

We have performed high-resolution structural and chemical characterization of the native oxide films formed on a ferritic Fe- 13 at. % Cr alloys at different stages of growth. The steady-state protective oxide film was found to be 5-6 nm thick, epitaxially grown, with a cubic spinel-structure ((Fe, Cr)3O4) and a Baker-Nutting orientation-relationsh...

High-entropy alloys are solid solutions of multiple principal elements that are capable of reaching composition and property regimes inaccessible for dilute materials. Discovering those with valuable properties, however, too often relies on serendipity, because thermodynamic alloy design rules alone often fail in high-dimensional composition spaces...

Fe- and steelmaking is the largest single industrial CO2 emitter, accounting for 6.5% of all CO2 emissions on the planet. This fact challenges the current technologies to achieve carbon-lean steel production and to align with the requirement of a drastic reduction of 80% in all CO2 emissions by around 2050. Thus, alternative reduction technologies...

Stacking faults (SFs), similar to other planar defects such as grain boundaries, twin boundaries and heterogeneous interfaces, can be tailored to simultaneously increase strength and ductility of metal matrix composites. However, SFs are rarely observed in Al alloy matrix composites, resulting from the high stacking fault energy (SFE) (166 mJ/m²) o...

Advanced lightweight high-strength steels are often compositionally and microstructurally complex. While this complex feature enables the activation of multiple strengthening and strain-hardening mechanisms, it also leads to a complicated damage behavior, especially in the presence of hydrogen (H). The mechanisms of hydrogen embrittlement (HE) in t...

In conventional processing, metals go through multiple manufacturing steps including casting, plastic deformation, and heat treatment to achieve the desired property. In additive manufacturing (AM) the same target must be reached in one fabrication process, involving solidification and cyclic remelting. The thermodynamic and kinetic differences bet...

Deformation twinning is rarely found in bulk face-centered cubic (FCC) alloys with very high stacking fault energy (SFE) under standard loading conditions. Here, based on results from bulk quasi-static tensile experiments, we report deformation twinning in a micrometer grain-sized compositionally complex steel (CCS) with a very high SFE of~79 mJ/m...

Deformation twinning is rarely found in bulk face-centered cubic (FCC) alloys with very high stacking fault energy (SFE) under standard loading conditions. Here, based on results from bulk quasi-static tensile experiments, we report deformation twinning in a micrometer grain-sized compositionally complex steel (CCS) with a very high SFE of ~79 mJ/m...

The enormous magnitude of 2 billion tons of alloys produced per year demands a change in design philosophy to make materials environmentally, economically, and socially more sustainable. This disqualifies the use of critical elements that are rare or have questionable origin. Amongst the major alloy strengthening mechanisms, a high-dispersion of se...

There are several facets of aluminum when it comes to sustainability. While it helps to save fuel due to its low density, producing it from ores is very energy-intensive. Recycling it shifts the balance towards higher sustainability, because the energy needed to melt aluminum from scrap is only about 5% of that consumed in ore reduction. The amount...

Significance About 90% of all mechanical service failures are caused by fatigue. Avoiding fatigue failure requires addressing the wide knowledge gap regarding the micromechanical processes governing damage under cyclic loading, which may be fundamentally different from that under static loading. This is particularly true for deformation-induced mar...

High-entropy alloys are solid solutions of multiple principal elements, capable of reaching composition and feature regimes inaccessible for dilute materials. Discovering those with valuable properties, however, relies on serendipity, as thermodynamic alloy design rules alone often fail in high-dimensional composition spaces. Here, we propose an ac...

Ever more stringent regulations on greenhouse gas emissions from transportation motivate efforts to revisit materials used for vehicles1. High-strength aluminium alloys often used in aircrafts could help reduce the weight of automobiles, but are susceptible to environmental degradation2,3. Hydrogen ‘embrittlement’ is often indicated as the main cul...

Steel production causes a third of all industrial CO2 emissions due to the use of carbon-based substances as reductants for iron ores, making it a key driver of global warming. Therefore, research efforts aim at replacing these reductants with sustainably produced hydrogen. Hydrogen-based direct reduction (HyDR) is an attractive processing technolo...

Fossil-free ironmaking is indispensable for reducing massive anthropogenic CO2 emissions in the steel industry. Hydrogen-based direct reduction (HyDR) is among the most attractive solutions for green ironmaking, with high technology readiness. The underlying mechanisms governing this process are characterized by a complex interaction of several che...

The ultimate goal for structural materials is achieving both high strength and ductility. However, increasing one of these properties can usually decrease the other, resulting in the so-called strength-ductility trade-off. According to the Considère criterion, increased strain hardening rates are demanded at higher strains to prevent necking and st...

The third-generation advanced high strength medium manganese steels aim at high-performance automobile sheet steel applications. Micro-alloying of steels is considered an effective method to enhance mechanical properties through grain refinement and precipitation hardening. However, in the context of cold-rolled, intercritically annealed medium-man...

Fossil-free ironmaking is indispensable for reducing massive anthropogenic CO2 emissions in the steel industry. Hydrogen-based direct reduction (HyDR) is among the most attractive solutions for green ironmaking, with high technology readiness. The underlying mechanisms governing this process are characterized by a complex interaction of several che...

To develop novel Invar alloys in the practically infinite compositional space of multicomponent alloys, rapid alloy prototyping is used to investigate five multicomponent Invar alloys with 5 at.% addition of Al, Cr, Cu, Mn and Si to a super Invar alloy (Fe63Ni32Co5; at.%), respectively. All alloys show abnormally low thermal expansion coefficients...

The influence of hydrogen on the mechanical behavior of Inconel 718 fabricated by laser powder-bed-fusion was investigated through a series of tensile experiments. Samples subjected to two different post-fabrication heat treatments, viz. direct aging (DA) and homogenization plus aging (HA), were tested. Detailed microstructural characterization sho...

Ever more stringent regulations on greenhouse gas emissions from transportation motivate efforts to revisit materials used for vehicles. High-strength Al-alloys often used in aircrafts could help reduce the weight of automobiles, but are susceptible to environmental degradation. Hydrogen (H) "embrittlement" is often pointed as the main culprit, how...

The third-generation advanced high strength medium manganese (3–12 wt.%) steels typically consist of ultrafine-grained dual-phase (austenite-ferrite) microstructure, obtained through the intercritical annealing of martensite at temperatures typically ≤ 0.5Tmelt, where the bulk diffusion of Mn is extremely slow. Yet, the manganese partitioning plays...

The design of high performance structural materials is always pursuing combinations of excellent yet often mutually exclusive properties such as mechanical strength, ductility and thermal stability. Although crystal-glass composite alloys provide better ductility compared to fully amorphous alloys, their thermal stability is poor, due to heterogene...

Parts produced by laser powder-bed fusion (LPBF) show unique microstructures consisting of dislocation structures and an oxide nanoparticle dispersion usually embedded in epitaxially-grown grains. Thermomechanical processing is an alternative to enhance the microstructure of such materials. However, the deformation mechanisms and the resulting micr...

Alloys manufactured by laser powder-bed fusion have intrinsic and hierarchical microstructural features inherited from fast solidification (up to 10⁴ K/s) and subsequent thermal cycles. This creates epitaxial grains, dislocation cell structures, and second-phase oxide nanoparticles. Epitaxial grains follow a pattern where finer grains are found in...

The lack of strength and damage tolerance can limit the applications of conventional soft magnetic materials (SMMs), particularly in mechanically loaded functional devices. Therefore, strengthening and toughening of SMMs is critically important. However, conventional strengthening concepts usually significantly deteriorate soft magnetic properties,...

Medium manganese steels are promising alloys for highly demanding sheet steel applications. However, cold-rolled intercritically annealed ultrafine-grained dual-phase medium manganese steels exhibit Lüders banding, which is detrimental for the mechanical properties and for the surface finish after forming. Therefore, it is essential to prevent the...

Iron- and steelmaking is the largest single industrial CO2 emitter, accounting for 6.5% of all CO2 emissions on the planet. This fact challenges the current technologies to achieve carbon-lean steel production and to align with the requirement of a drastic reduction of 80% in all CO2 emissions by around 2050. Thus, alternative reduction technologie...

Dislocations are one-dimensional defects in crystals, enabling their deformation, mechanical response, and transport properties. Less well known is their influence on material chemistry. The severe lattice distortion at these defects drives solute segregation to them, resulting in strong, localized spatial variations in chemistry that determine mic...

By considering the valence-electron concentration of 3d transition-metal alloys and compounds, we develop 3d high-entropy alloy Mn12.1Fe34.2Co33.5Ni12.3Cu7.9 with 8.7 electrons per atom, which is identical to that of Fe65Ni35 Invar. We carry out x-ray diffraction, scanning electron microscopy, magnetization, thermal expansion, and elastic modulus m...

Hydrogen embrittlement (HE) is one of the most dangerous yet most elusive embrittlement problems in metallic materials. Advanced high-strength steels (AHSS) are particularly prone to HE, as evidenced by the serious degradation of their load-bearing capacity with the presence of typically only a few parts-per-million H. This strongly impedes their f...

In this study, we reveal that strain partitioning control is an essential technique to improve the mechanical response of medium-Mn steels by the micro digital image correlation analysis. An Fe-12Mn-0.06C-3Al (wt%) steel, which shows transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP), was used as a model alloy. Two alte...

Twinning induced plasticity (TWIP) and phase transformation induced plasticity (TRIP) are two effective mechanisms for achieving good combination of strength and ductility in metallic materials, such as steels and high entropy alloys (HEAs). A further enhancement of the strength-ductility combination can be achieved by grain refinement owing to the...

Segregation to grain boundaries affects their cohesion, corrosion, and embrittlement and plays a critical role in heterogeneous nucleation. In order to quantitatively study segregation and low-dimensional phase separation at grain boundaries, here, we apply a density-based phase-field model. The current model describes the grain-boundary thermodyna...