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Background: Compression experiments are widely used to study the mechanical properties of materials at micro- and nanoscale. However, the conventional engineering stress measurement method used in these experiments neglects to account for the alterations in the material's shape during loading. This can lead to inaccurate stress values and potentially misleading conclusions about the material's mechanical behavior, especially in the case of localized deformation. Objective: Our goal is to calculate true stress in cases of localized plastic deformation from standard experimental data (displacement-force curve, aspect ratio, shear band angle and elastic strain limit). Methods: We use a simple mechanical-geometrical approach based on reasonable physical assumptions to get analytic formulas of true stress and eliminating the need for finite element computations. Furthermore, in numerical simulations of pillar compression, the formula-based true stress demonstrates strong alignment with the theoretical true stress. Results: We propose analytic formulas for calculating true stress in cases of localized plastic deformation commonly encountered in experimental settings for a single band oriented in arbitrary directions with respect to the vertical axis of the pillar. Conclusions: The true stress computed with the proposed formulas provides a more precise interpretation of experimental results and can serve as a valuable and simple tool in material design and characterization. [ABSTRACT FROM AUTHOR]

In the contemporary era, the enhancement of wearable capacitive sensors is achieved through the utilization of polymeric micropillars as filler materials between electrode plates. To gain a deeper understanding of the dynamic response of the system, nonlinear coupled governing equations of a circular microplate motion resting on an array of polymeric micropillars have been derived. These equations are used to model the system's behavior. In addition, the squeezing motion of the micro-pillars is characterized using the incompressible Neo-Hookean model. Both static and dynamic responses, including transient and steady-state solutions, are investigated in detail by discretizing over spatial coordinates using a weak formulation approach. A frequency response analysis is conducted using a continuation-based method. This entails expanding the steady-state solution using a Fourier transform and employing the energy balance principle. The unknown coefficients of the expansion series are calculated using a gradient descent-based learning approach that is physically motivated. Furthermore, a dynamic step size strategy for frequency increments is employed to effectively follow the solution path. This strategy is implemented via the ARC length method. In this study, we examine the impact of varying PDMS (polydimethylsiloxane) hydrogel mechanical and geometrical configurations. It can be reasonably concluded that the mechanical properties of the pillars and the geometrical configuration of the circular plate and micropillars have a significant impact on the maximum tolerable pressure, fast transient response, and frequency response analysis. [ABSTRACT FROM AUTHOR]

Abstract In the contemporary era, the enhancement of wearable capacitive sensors is achieved through the utilization of polymeric micropillars as filler materials between electrode plates. To gain a deeper understanding of the dynamic response of the system, nonlinear coupled governing equations of a circular microplate motion resting on an array of polymeric micropillars have been derived. These equations are used to model the system’s behavior. In addition, the squeezing motion of the micro-pillars is characterized using the incompressible Neo-Hookean model. Both static and dynamic responses, including transient and steady-state solutions, are investigated in detail by discretizing over spatial coordinates using a weak formulation approach. A frequency response analysis is conducted using a continuation-based method. This entails expanding the steady-state solution using a Fourier transform and employing the energy balance principle. The unknown coefficients of the expansion series are calculated using a gradient descent-based learning approach that is physically motivated. Furthermore, a dynamic step size strategy for frequency increments is employed to effectively follow the solution path. This strategy is implemented via the ARC length method. In this study, we examine the impact of varying PDMS (polydimethylsiloxane) hydrogel mechanical and geometrical configurations. It can be reasonably concluded that the mechanical properties of the pillars and the geometrical configuration of the circular plate and micropillars have a significant impact on the maximum tolerable pressure, fast transient response, and frequency response analysis.

Additive manufacturing makes fabricating titanium alloy components directly into their near-net shapes possible, reducing the need for machining. However, post-additive manufacturing machining becomes necessary for immediate design adjustments, dimension alterations, and surface quality enhancement. The inherent thermal effects during additive manufacturing make machining challenging due to altered mechanical properties from their wrought counterpart, including increased strength and hardness with reduced ductility. Textured cutting tools are being widely used to enhance the machinability of superalloys. In this work, micro-pillar type textures, created using Reverse Micro Electrical Discharge Machining (RμEDM) on tungsten carbide inserts, aimed to explore machinability in turning operations on selective laser melted (SLM) titanium alloy. The study investigates micro-pillar interaction with SLM Ti6Al4V in chip behavior, tool morphology, cutting forces, and surface roughness under various cutting fluid strategies. Under Minimum Quantity Lubrication (MQL), textured tools show significant improvements, producing untangled chips with reduced curl radius. A considerable decrease of 38 % in the tool/chip contact area indicates a substantial reduction in the seizure zone, hence a decline in the temperature rise of the cutting tool. Dry conditions show a 20.4 % reduction in flank wear width, suggesting prolonged cutting-edge sharpness due to tool texturing. In MQL conditions, a maximum 28.9 % reduction in feed force is observed, indicating improved frictional conditions at the interface. Additionally, a 10.4 % improvement in surface finish is achieved. The work is summarized by claiming micro-pillar textured tools enhance the machinability of additively manufactured Ti6Al4V demonstrated through improvements in titanium adhesion, cutting-edge sharpness, feed force, and surface finish, particularly MQL conditions. [Display omitted] • Fabrication of novel micro-pillar textures on tungsten carbide inserts using RμEDM. • Machining under dry, compressed air, minimum quantity lubrication, and wet conditions. • Investigation of forces, surface roughness, tool wear, and chip morphology is performed. • Enhanced machinability of SLM Ti6Al4V due to micro-texturing of the rake face. • Reduced tool-chip contact and enhanced CF penetration are witnessed in textured tools. [ABSTRACT FROM AUTHOR]

Graphical Abstract

Laser surface texturing and through-mask electrochemical micromachining (TMECMM) are some of the commonly used methods which include multiple steps to achieve micro-textures. However, for large-area applications, it is desirable to have an economical single-step process. In this regard, ECMM is expected to be a promising and economically viable micro-texturing process for micro-manufacturing industries. This paper proposes a novel maskless EC micro-texturing process using tool sinking technique with low voltage and short pulses. Methodology of using edges (∼30 μm each) of printed circuit boards (PCBs) for ECMM of micro-channels and micro-pillars is a unique one. Micro-pillars, micro-dimples and micro-channels are produced through a direct electrochemical cathode sinking process. Analysis of current density and prediction of width and depth of micro-dimples on a flat stainless steel surface are studied through 2D numerical simulation carried out on COMSOL 4.3a. The proposed method implies the use of less toxic electrolyte, low voltage (1-6 V), short pulses (5 to 50 μs) and selective polymer coating on the tool (cathode). A series of experiments of EC sinking for creating various micro-patterns and micro-structures has been carried out on the flat as well as curved metallic surfaces. This paper reports machining of micro-dimples of 200-300 μm diameter, micro-channels of 150-250 μm and square micro-pillars of 300-350 μm. Comparison of the predicted geometrical dimensions of the micro-dimples through the simulation shows reasonable agreement with the experimental results for the given process parameters of ECMM. The paper also reports a brief comparison of laser surface texturing (LSTex) and electrochemical surface texturing (ECSTex). [ABSTRACT FROM AUTHOR]

Highlights • A droplet actuation and manipulation mechanism using freely available surface energy is demonstrated without using external force. • The presented technique can avoid unwanted secondary effects due to external actuation. • Droplet transportation using experimental selective painting surface is validated with lattice Boltzmann model. • A new approach to design lab-on-chip using micro-pillar surface is discussed in LBM framework. Abstract In the digital microfluidic systems, the droplet actuation and control in a chip is an important requirement. Usually, to actuate any droplet operation, an external energy needs to be supplied. We have demonstrated the utilization of the freely available surface energy by the suitable design of partial wetting surfaces to actuate and perform various droplet operations like splitting, transportation and merging. This approach would help us to realize on-chip droplet operations without applying external force like pressure, electric field or magnetic field with required control. The partial wetting surface and interface are synthesized using a selective painting technique and basic operations such as impingement, spreading and transportation are demonstrated. These dynamic properties of the droplet are modelled and analyzed with a multiphase lattice Boltzmann method (LBM). The partial wetting study of droplet dynamics is demonstrated using chemical gradient and structural gradient. The modelling results show good agreement with the experimental study, thus LBM can be used as tool for analyzing such chip designs. Further a microfluidic chip is designed with partial wetting surfaces chemically and by the placement of micro-pillars and basic on-chip operations such as splitting, merging and transportation are illustrated using LBM. [ABSTRACT FROM AUTHOR]

The physico-chemical surface design of implants influences the surrounding cells. Osteoblasts on sharp-edged micro-topographies revealed an impaired cell phenotype, function and Ca2+ mobilization. The influence of edges and ridges on the Wnt/β-catenin pathway in combination with the cells’ stress response has not been clear. Therefore, MG-63 osteoblasts were studied on defined titanium-coated micro-pillars (5 × 5 × 5 µm) in vitro and in silico. MG-63s on micro-pillars indicated an activated state of the Wnt/β-catenin pathway. The β-catenin protein accumulated in the cytosol and translocated into the nucleus. Gene profiling indicated an antagonism mechanism of the transcriptional activity of β-catenin due to an increased expression of inhibitors like ICAT (inhibitor of β-catenin and transcription factor-4). Cells on pillars produced a significant reactive oxygen species (ROS) amount after 1 and 24 h. In silico analyses provided a detailed view on how transcriptional activity of Wnt signaling is coordinated in response to the oxidative stress induced by the micro-topography. Based on a coordinated expression of regulatory elements of the Wnt/β-catenin pathway, MG-63s are able to cope with an increased accumulation of β-catenin on micro-pillars and suppress an unintended target gene expression. Further, β-catenin may be diverted into other signaling pathways to support defense mechanisms against ROS.

Laser surface texturing (LST) processes have great potential to alter surface wetting properties of widely known bioactive Ti–6Al–4V alloy. Micro-pillars arrays of different topography are produced by Nd:YAG laser of 1064 nm wavelength to investigate the influence of its physical and geometrical parameter on wettability. Micro-textures named as: T HS (high density, square pillars of 30 × 30 μm), T MS (medium density, square pillars of 60 × 60 μm), T LS (low density, square pillars of 170 × 170 μm), T LL (low density, landscape pillars of 300 × 100 μm) and T LP (low density, portrait pillars of 100 × 300 μm) are produced to analyze the effect of texture areal density, aspect ratio and shape over surface wetting phenomenon. It is observed that on the flat textured surface shows hydrophilic and spontaneous wetting behavior up to 24 h after machining. Percentage increment in water contact angle (CA) value varies with time, maximum increase in CA was found to be in T HS (215%) followed by T MS (197%), T LS (166%), T LP (144%) and T LL (122%) after 20 days of machining (as compared with the untextured surface). The response of the textured surface to spontaneous wetting behavior with respect to varying viscosity is also studied and validated through Washburn's model. It is found that early viscous regime of capillary rise in the textured surface can be altered by regulating the geometrical parameters of the micro-textures array. Time taken to rise up to 40 mm by low, medium and high viscosity fluids are 200 s, 600 s and 9334 s respectively. The texture ( T HS ) with highest areal density micro-pillars of 60 μm width exhibits maximum capillary action. [ABSTRACT FROM AUTHOR]

Al-Zn alloys were processed by high-pressure torsion (HPT) to produce ultrafine-grained (UFG) materials. For low Zn contents, HPT gave strengthening due to grain refinement while for the highest Zn concentration the decomposition of the microstructure yielded an abnormal softening at room temperature. The microstructure decomposition led also to the formation of a Zn-rich phase which wet the Al/Al grain boundaries and enhanced the role of grain boundary sliding with unusually high strain rate sensitivity. The occurrence of intensive sliding in these UFG alloys is demonstrated by deforming micro-pillars. [ABSTRACT FROM AUTHOR]

Deep proton writing (DPW) is a fabrication technology developed for the rapid prototyping of polymer micro-structures. We use SU-8, a negative resist, spincoated in a layer up to 720 μm-thick in a single step on borosilicate glass, for irradiation with a collimated 12 MeV energy proton beam. Micro-pillars with a slightly conical profile are irradiated in the SU-8 layer. We determine the optimal proton fluence to be 1.02 × 10 4 μm −2 , with which we are able to repeatably achieve micro-pillars with a top-diameter of 138 ± 1 μm and a bottom-diameter of 151 ± 3 μm. The smallest fabricated pillars have a top-diameter of 57 ± 5 μm. We achieved a root-mean-square sidewall surface roughness between 19 nm and 35 nm for the fabricated micro-pillars, measured over an area of 5 × 63.7 μm. We briefly discuss initial testing of two potential applications of the fabricated micro-pillars. Using ∼100 μm-diameter pillars as waveguides for gigascale integration optical interconnect applications, has shown a 4.7 dB improvement in optical multimode fiber-to-fiber coupling as compared to the case where an air–gap is present between the fibers at the telecom wavelength of 1550 nm. The ∼140 μm-diameter pillars were used for mold fabrication with silicone casting. The resulting mold can be used for hydrogel casting, to obtain hydrogel replicas mimicking human tissue for in vitro bio-chemical applications. [ABSTRACT FROM AUTHOR]

We report on the design, fabrication, and characterization of a reflective transmitter targeting implementation in passive optical networks (PON) with frequency division multiplexed access (FDMA). It is made up of a Silicon photonic integrated circuit (Si-PIC) comprising a reflective Mach Zehnder modulator and its flip-chipped CMOS electronic integrated circuit driver, the two ICs being interconnected by means of high density and low parasitic copper micro pillars. Several transmissions, in an FDMA PON context, are successfully demonstrated using 500 MBaud QPSK and 16-QAM modulated subcarriers, achieving bit error rate below 2.10−3. For QPSK-modulated subcarriers (respectively, 16-QAM), the available access frequency bandwidth is measured to be 1–7 GHz (respectively, 2–4 GHz) with an available loss budget of 9 dB (respectively, 5 dB). Improvements of the Si-PIC are further identified to achieve compliancy with 31 dB ODN loss. [ABSTRACT FROM PUBLISHER]

The achievement of an adequate accuracy of the microinjection molding process applied to the replication of micro-features is a complex task. The selection of process parameters and the geometry of the molded part influences the filling flow of the melt inside the mold cavity as well as the final quality of the replicated micro-features. In this work, the replication of a micro-structured surface is studied in relation to the thickness of the molded part. In particular, the effects of a rapid heat cycle molding process, cavity air evacuation, part thickness are experimentally evaluated. The analysis of the experimental data showed that the thickness of the main flow region and the molding temperature are significant factor affecting the replication quality. In particular, a combination of small cavity thickness and a high mold temperature (above T g ) can be effective in increasing the replicated height of micro-features. Experimental results also point out the correlation between the holding pressure and the distance from the injection location. An effective approach to the design of both the part and the process, should consider that the selection of process parameters must be related to design of the mold cavity. [ABSTRACT FROM AUTHOR]

A micro-structured nickel insert was investigated for polyether ether ketone (PEEK) injection moulding. The micro-features were circular holes 4 μm in diameter and 2 μm deep, with a 2-μm edge-to-edge distance. Six thousand moulding cycles were operated. Half of the insert was coated by approximately 200 nm CrN. PEEK parts produced by the coated side and uncoated side were compared. Coating thickness was measured at intervals of production and employed to characterize the coating wear. Pillar geometry at fixed locations on PEEK parts was studied by scanning electron microscope (SEM). Energy-dispersive X-ray spectroscopy (EDS) was conducted on the PEEK parts in order to study the possible nickel and silver contamination. The results show that the studied coating had a very low wear, and no nickel or silver contamination on PEEK was detected for both parts produced by coated and uncoated sides. Coating improved demoulding by reducing small indentations on pillars. [ABSTRACT FROM AUTHOR]

Three dimensional dislocation dynamics ( DD ) simulations are performed to investigate the governing mechanism of size dependent plastic deformation in submicron face-centered cubic ( fcc ) micropillars under uniaxial loading. Based on previous atomistic simulations, we introduce an algorithm for dislocation nucleation at the free surface as a function of stress and temperature in the DD simulation. The simulation results show stochastic behaviors in agreement with experimental observations, and reveal that dislocation nucleation at the free surface is the dominant mechanism of plastic flow in small pillars with diameters less than 200 nm, while the operation of truncated dislocation sources is the governing mechanism in large pillars with diameters exceeding 1 μm. In between, both mechanisms come into play in a stochastic way. [ABSTRACT FROM AUTHOR]

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Experimental and numerical studies of the behavior of a slurry in a shear flow over a rough surface with a defined micro-structure are presented. A new ring shear device was built which contains an optically transparent test chamber. Its bottom wall contains arrays of micro-cantilever force sensors simulating a defined surface roughness created by deep-etching of micro-pillars in a silicon wafer. The results of visual observation of the interaction of the suspension with the structured surface during severe deformation are shown. Observations comprise the liquid phase motion, i.e., the interaction between the liquid phase and solid particles, the movement of separate particles and their interactions with the micro-pillars. Abrupt changes in rotational motion and translational velocity of particles are observed that induce mutual collisions and successive formation and break-up of cluster structures of various types. In addition to the experiments the process was simulated with discrete element (DEM) simulations. Many characteristics found in the experiments are reproduced by the simulations. Furthermore the physical quantities of the process like contact forces or velocities can be quantified which helps us to develop more detailed models of the abrasive behavior of slurries. [ABSTRACT FROM AUTHOR]

Microglia are the resident macrophages of the central nervous system and contribute to maintaining brain's homeostasis. Current 2D "petri-dish" in vitro cell culturing platforms employed for microglia, are unrepresentative of the softness or topography of native brain tissue. This often contributes to changes in microglial morphology, exhibiting an amoeboid phenotype that considerably differs from the homeostatic ramified phenotype in healthy brain tissue. To overcome this problem, multi-scale engineered polymeric microenvironments are developed and tested for the first time with primary microglia derived from adult rhesus macaques. In particular, biomimetic 2.5D micro- and nano-pillar arrays (diameters = 0.29-1.06 µm), featuring low effective shear moduli (0.25-14.63 MPa), and 3D micro-cages (volume = 24 × 24 × 24 to 49 × 49 × 49 μm 3 ) with and without micro- and nano-pillar decorations (pillar diameters = 0.24-1 µm) were fabricated using two-photon polymerization (2PP). Compared to microglia cultured on flat substrates, cells growing on the pillar arrays exhibit an increased expression of the ramified phenotype and a higher number of primary branches per ramified cell. The interaction between the cells and the micro-pillar-decorated cages enables a more homogenous 3D cell colonization compared to the undecorated ones. The results pave the way for the development of improved primary microglia in vitro models to study these cells in both healthy and diseased conditions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Sharaf, Roos, Timmerman, Kremers, Bajramovic and Accardo.)

To explore the deformation mechanism of α-Ti with high oxygen doping, micro-pillars of single crystal with orientations of near 0°, 45°, and 90° inclined to c -axis were fabricated via focused ion beam (FIB) milling from a high oxygen content commercial purity Ti (CP–Ti). The micro-pillars were loaded under quasi-static compression. Post-mortem analysis reveals that only prismatic slip activated for 45° and 90° oriented samples with their critical resolved shear stress (CRSS) values of about 457 MPa and 596 MPa, and only {10–11}< c + a > the first-order pyramidal slip activated on the 0° sample with a CRSS of around 1019 MPa. The results suggest that the oxygen addition remarkably reduces the CRSS ratio between non-prismatic and prismatic slips of α-Ti. In addition, the results indicate that the Schmid law may not be applicable for α-Ti single crystal at micro-size level. [ABSTRACT FROM AUTHOR]

The interface debonding caused by mismatched thermal expansion is a key issue in graphene nanoplatelets/Ti matrix composites (GNPs/TiMCs), which significantly decreases the composites' mechanical properties. In this study, GNPs/Ti composites were fabricated by spark plasma sintering (SPS) followed by heat treatment (HT) routes. A novel strategy that strengthening the GNPs-Ti interface bonding via tailored three-dimensional (3D) interface configuration was proposed for the first time. Characters of interface evolution (before and after HT processes) were discussed detailedly in conjunction with the in-situ formed TiB whiskers (TiBw). The interfacial microstructure displayed that GNPs was used as template for the heteroepitaxial growth of TiBw, then TiBw connected the TiC layer and the adjacent Ti matrix. Tensile tests showed that GNPs-(TiBw)/Ti composites exhibited excellent strength-plasticity compatibility as compared to GNPs/Ti. Ex-situ compression tests of micro-pillars fabricated from the bulk composites revealed that the 3D interface configuration in GNPs-(TiBw)/Ti possessed significantly higher strain accommodation and strain-hardening ability during deformation. This study highlights the importance of interface optimization, which is helpful for developing the interfacial engineering and achieving good properties in GNPs/TiMCs. [ABSTRACT FROM AUTHOR]

The physico-chemical surface design of implants influences the surrounding cells. Osteoblasts on sharp-edged micro-topographies revealed an impaired cell phenotype, function and Ca2+ mobilization. The influence of edges and ridges on the Wnt/β-catenin pathway in combination with the cells' stress response has not been clear. Therefore, MG-63 osteoblasts were studied on defined titanium-coated micro-pillars (5 × 5 × 5 µm) in vitro and in silico. MG-63s on micro-pillars indicated an activated state of the Wnt/β-catenin pathway. The β-catenin protein accumulated in the cytosol and translocated into the nucleus. Gene profiling indicated an antagonism mechanism of the transcriptional activity of β-catenin due to an increased expression of inhibitors like ICAT (inhibitor of β-catenin and transcription factor-4). Cells on pillars produced a significant reactive oxygen species (ROS) amount after 1 and 24 h. In silico analyses provided a detailed view on how transcriptional activity of Wnt signaling is coordinated in response to the oxidative stress induced by the micro-topography. Based on a coordinated expression of regulatory elements of the Wnt/β-catenin pathway, MG-63s are able to cope with an increased accumulation of β-catenin on micro-pillars and suppress an unintended target gene expression. Further, β-catenin may be diverted into other signaling pathways to support defense mechanisms against ROS. [ABSTRACT FROM AUTHOR]

This research was devoted to studying the influence of the taper angle on the micro-compression of micro-pillars fabricated from near-amorphous and nanocrystalline Mo-B-C coatings. A series of micro-pillars with a taper angle between 4–14° was fabricated by focused ion beam technique. The deformation mechanism was found to be dependent on the taper and, also, on the crystallinity of the coating. In order to obtain correct values of yield strength and Young's modulus, three empirical models of stress correction were experimentally tested, and the results were compared with nanoindentation measurements. It was shown that the average stress correction model provided comparable results with nanoindentation for the yield strength for taper angles up to ~10°. On the other hand, the average radius or area model gave the most precise results for Young's modulus if the taper angle was <10°. [ABSTRACT FROM AUTHOR]

Objectives: A tearable dissolving microneedle system (TD-MN system) was developed for shortening the time required to administer drugs into the skin through the dissolving microneedles., Methods: TD-MN system consisted of an array of tearable dissolving microneedles (TD-MN) and micro-pillars. The microneedle tips had a female part to integrate with the micro-pillars. The micro-pillars exerted a vertical force to cause the separation of the tips from the base. The separation force exerted by six TD-MN arrays with different thicknesses of separation region was measured. The TD-MN system with trypan blue was inserted into porcine skin to observe the separation of the microneedle tips, and then calcein was added separately to observe drug diffusion into the skin., Results: The thickness of the tearable region and the depth of the female part were a function of the concentration and volume of the molding solution. The separation force increased as the thickness of the tearable region increased. Nine tips were successfully separated from the base by applying a force of through the micro-pillars., Conclusions: The TD-MN system could provide immediate administration of a drug, resulting in improved patient convenience as well as delivery of the correct drug dose.

By stabilising metastable austenite with a suitable morphology in a martensitic structure, it is possible to impart to multi-phase steels high ductility combined with tensile strengths exceeding 2000 MPa. One way to achieve such mixed structures consisting of martensite and retained austenite (RA) is the Q&P (quenching and partitioning) process. The resulting structure contains metastable austenite in the form of thin foils located between martensite laths or plates. The stability of austenite under mechanical loading is the essential factor contributing to the extraordinary plasticity of such materials during cold deformation. A steel with 0.43% of carbon, alloyed with manganese, silicon and chromium was chosen for the experiment described in the present paper. Using the Q&P process, a martensitic structure with 20% of retained austenite was obtained. As cold plastic deformation causes the austenite to transform, 10% cold deformation was applied after the Q&P process. This deformation reduced the RA fraction to 11%. Materials prepared by this method were examined using micro-pillar compression experiments. Using the focused ion beam (FIB) method, pillars of 3 × 3 μm cross-section and 8 μm length were fabricated. These were afterwards mechanically tested in situ in an electron microscope in quasi-static compression at a true strain rate of 3 × 10 −4 s −1 to different amounts of plastic strain. The experiment showed that mechanical properties of the two conditions of material differ in terms of yield strength and the strain hardening exponent. An additional metallographic analysis of structures, including the exploration of the influence of decomposition of retained austenite, was performed. [ABSTRACT FROM AUTHOR]