Exploring microstructural design and deformation mechanisms in TRIP-assisted steels with diverse martensitic-type start microstructure

Effect of strain rate on the microstructure evolution and superplastic deformation behavior of cold-rolled medium Mn lightweight steel

The evolution of the deformation micro-mechanisms and the dislocation structures in additively manufactured (AM) 316L steel was investigated via in-situ SEM/EBSD tensile tests coupled with fine TEM investigations at different strain levels. We show that the deformation mechanisms are strongly influenced by the initial dual-scale cellular structure, composed of large dislocation cells with chemically segregated cell walls, encapsulating smaller, chemically homogeneous internal regions. At low and medium strain levels, the primary deformation mode is dislocation slip across the dislocation cells interiors and formation of micro-bands while plastic deformation at higher strain is primarily controlled by mechanical nano-twins nucleated through the overlapping of stacking faults ribbons. Unlike conventional 316L, the AM 316L shows a nearly linear increase in dislocation density with increasing applied strain throughout the full range of plastic deformation. The initial cellular structure is preserved under plastic deformation, continuing to act as a barrier to dislocation glide and contributing to the high ductility of the AM 316L steel. A correlation between the work hardening rate and the observed deformation modes is evidenced, strengthening the conclusion that the plasticity of AM 316L is atypical. These findings enhance the understanding of the dislocation structures and the microstructure evolution during plastic deformation in AM 316L steel, providing valuable insights for the development of predictive large-scale plasticity models for these materials. • Microstructure evolution and deformation mechanisms in AM 316L were studied. • The deformation modes are mainly dictated by the initial dual-scale structure. • Pre-existing dislocation walls act as both sources and barriers to dislocation motion. • The evolution of the work hardening rate was correlated with the deformation modes.

Microstructure evolution and deformation mechanism of coherent L12-strengthened high-entropy alloy during sliding wear

Iron-dust magnets

Deformation mechanism of commercially pure titanium under biaxial loading at ambient and elevated temperatures

Microstructure evolution and deformation mechanism along the thickness of heavy-wall ferrite-bainite dual-phase offshore pipelines by the progressive forming process

A detailed understanding of the fatigue behavior of freestanding metallic films is crucial for extending the lifetime of microsensors and actuators. Previous investigations have pointed at cyclic creep as the dominant deformation mechanism in columnar gold thin films. Here, we investigate the widespread ultra-fine grained (UFG) and nanocrystalline (NC) microstructures, at typical operational temperatures from ambient to 100 °C. While the UFG films show low failure strains, the NC samples can withstand several percents strain, which was attributed to their high initial dislocation density. The combination of strength and ductility in NC films results in superior fatigue lifetimes compared to the UFG films for both low-cycle and high-cycle fatigue regimes. At the highest temperature, NC films even evidence an unexpected fatigue limit. Cyclic creep was evident for all microstructural conditions and temperatures. Hence, creep and diffusion processes are dominant, especially in the low dislocation density UFG gold films. In addition, NC films experience a reduction of the high-angle grain boundaries after cycling at 23 °C and local grain coarsening at 100 °C. • Comparison of the fatigue behavior of freestanding gold thin films of different microstructural conditions by stress-controlled bulge fatigue tests • The nanocrystalline (NC) films contain high initial dislocation density compared to the ultra-fine grained, columnar (UFG) condition, leading to improved strength and ductility • Enhanced LCF and HCF fatigue lifetime of NC films at all temperatures, and evidence of previously unreported fatigue limit at 100 °C • Transmission electron micrographs of samples cycled at 100 °C evidence locally coarsened grains with newly formed dislocations inside NC films and grain boundary grooving in UFG specimens • Cyclic creep is present in all films, with the activation energy pointing at creep and diffusion mechanisms controlling the fatigue deformation in both microstructures

Effect of pre-deformation on microstructure characteristics, texture evolution and deformation mechanism of AZ31 magnesium alloy

Microstructural Development and Deformation Mechanisms during Cold Rolling of a Medium Stacking Fault Energy TWIP Steel

Dynamic deformation and fracture of mullite (3Al2O3·2SiO2) ceramics under hypervelocity impact

The single-crystalline Co-9Al-7.5W-2Ta (at.%) superalloy shows pronounced directional coarsening of the γ′ phase (N-type rafting) during high-temperature/low-stress creep due to the highly positive γ/γ′ lattice misfit. High-resolution X-ray diffraction (HRXRD) experiments at room temperature show that the qualitative evolution of the recorded diffraction line profiles after creep deformation strongly depends on the crystallographic direction with respect to the direction of the applied creep load. This evolution of the line profiles also reflects the microstructural changes associated with rafting. By using an advanced data deconvolution approach for diffraction peak fitting, it is found that both in [001] parallel and in [010]/[100] perpendicular to the applied stress, respectively, the lattice plane spacings (d spacings) of the horizontal γ channels and the γ′ phase each tend towards a common value with increasing plastic strain. These values are associated with their respective unconstrained values. As a consequence, the γ/γ′ d spacing mismatch observed after plastic deformation is closely related to the mismatch of the unconstrained phases. The matrix tetragonal distortion and stresses strongly decrease. Combining these findings with the ones from earlier TEM studies on that alloy indicates that this is attributed to the relaxation of the overall stress induced by the ongoing formation of interfacial dislocation networks. The findings of this study help to understand the correlation between the evolution of lattice distortions and internal stresses and the microstructural changes and deformation mechanisms during N-type rafting of superalloys. Graphical abstract

Additive and subtractive hybrid manufacturing offers great potential for the integrated fabrication of high-performance structural components. CoCrNi MEA specimens were subjected to subtractive manufacturing (SM) immediately after additive manufacturing (AM) at elevated temperatures, forming a gradient microstructure approximately 100 µm in depth through the coupling of thermal and mechanical effects. The near-machined surface exhibited interactions between mechanical twins and stacking faults, which refined grains and promoted nanocrystals. Dynamic recrystallization (DRX) further refined the nanocrystalline structure, improving residual stress distribution and enhancing strain hardening. Three key mechanisms contributed to the enhanced properties. First, the transition from tensile to compressive residual stress introduced by surface plastic deformation effectively suppressed crack initiation and promoted ductility. Second, DRX activated under elevated temperatures homogenised the refined grain structure and improved strain compatibility. Third, the synergistic activation of stacking fault-induced plasticity, twinning-induced plasticity, and strain gradient hardening stabilised plastic flow and delayed strain localisation. Compared to specimens subjected to SM at room temperature (with ∼60 µm inhomogeneous gradient layer), subjecting the specimen to SM at an elevated temperature led to notable improvements in yield strength (25%), tensile strength (33%), and elongation (70%) over the AM-fabricated MEA specimen, demonstrating a clear synergy between strength and ductility.

Microstructural evolution and deformation mechanism of a Fe-15Mn alloy investigated by electron back-scattered diffraction and transmission electron microscopy

Microstructural evolution and high-temperature deformation mechanism of 4Cr5MoSiV1Ti steel

Effects of alloying addition on deformation mechanisms, microstructure, texture and mechanical properties in Fe-12Mn-0.5C austenitic steel