Plasticizing Effect Research Articles

Microwave spheronization of polyetherimide powder in plasticizer liquids for laser powder bed fusion

Preparing spherical powders from high-performance engineering plastics is usually challenging due to their high characteristic temperatures and excellent chemical resistance. This study reported an innovative liquid-phase microwave heating method for rapid spheronization of amorphous polyetherimide (PEI) powder and explored the processability of resultant powder in laser powder bed fusion (PBF-LB). The results indicated that the microwave process conditions, including the type of plasticizer liquids and microwave time, significantly influenced the spheronization effect and physicochemical properties of the powder. The plasticizing effect of the liquid largely reduced the glass transition temperature and melt viscosity of PEI particles, promoting their spheronization process. Spheronization enhanced the PBF-LB processability of PEI powder and reduced structural defects in parts, thereby leading to improved mechanical properties. Furthermore, its valuable flame-retardant properties were largely preserved. These findings showed the power of microwave spheronization in plasticizer liquids for advancing the application of optimized high-performance engineering plastic powders in the field of PBF-LB.

Preparation and characterization of poly(vinyl pyrrolidone)/cellulose nanofiber/Aloe Vera composites as a biocompatible hydrating facial mask

This study aimed to enhance the properties of polyvinylpyrrolidone (PVP) for use as biocompatible facial masks. To achieve this, nanofibers were developed by blending PVP with cellulose nanofibers (CNFs) and Aloe vera (AV) powder using electrospinning. The results showed that incorporating CNFs and AV into the PVP matrix led to the formation of smooth and uniform nanofibers. In particular, adding 3–6 wt% AV powder in PVP/CNF composites improved fiber diameter distribution and uniformity compared to pure PVP. The PVP/CNF/AV nanofibers exhibited desirable properties for facial mask applications. They displayed 86–93 % porosity, which allowed for efficient moisture absorption capacity of up to 1829 %, and excellent water vapor permeability rate of 3.92 g/m2h. The mechanical properties of the electrospun nanofiber composites were evaluated through tensile testing. The results showed that Young's modulus values decreased progressively with the addition of CNFs and AV powder to the PVP polymer matrix, indicating a plasticizing effect that enhances flexibility. The fracture strain remained similar across all composites, suggesting that CNFs and AV did not significantly weaken the PVP matrix. The tensile strength initially increased with CNF addition but decreased with incremental AV loading. Biocompatibility studies revealed that all nanofibers exhibited excellent fibroblast viability, surpassing 98 %. This indicates that incorporating CNFs and AV did not compromise cell viability, further highlighting the suitability of the PVP/CNF/AV composites for facial mask applications.

The design of appropriate Si content overcomes the strength-ductility trade-off in dual-phase high entropy alloy

To reduce the stacking fault energy (SFE) of the alloys, silicon (Si) was introduced into Fe40Mn35Co20Cr5 dual-phase high entropy alloys (HEAs). We propose a novel mechanism supported by first-principles calculations that predicts Si atoms may preferentially substitute Cr atoms, resulting in enhanced lattice distortion and reduced SFE. Experimental results indicate that incorporating 0.2 wt % Si enhances the ductility of the alloy while maintaining its strength through a synergistic effect involving dislocations and phase transformation. Furthermore, in the Si0.2 alloy, the integrity of 9 R structures were preserved, thereby enhancing the transformation-induced plasticity (TRIP) effect and facilitating attainment of an optimal balance between strength and ductility. However, incorporation of 0.1 wt % and 0.3 wt % Si content leads to a decline in ultimate tensile strength due to improper Si content causing grain growth and premature phase transition. Therefore, meticulous selection of an appropriate Si content is crucial for simultaneously enhancing both strength and ductility.

Microhabitat acclimatization alters sea anemone-algal symbiosis and thermal tolerance across the intertidal zone.

Contemporary symbioses in extreme environments can give an insight into mechanisms that stabilize species interactions during environmental change. The intertidal sea anemone, Anthopleura elegantissima, engages in a nutritional symbiosis with microalgae similar to tropical coral, but withstands more intense environmental fluctuations during tidal inundations. In this study, we compare baseline symbiotic traits and their sensitivity to thermal stress within and among anemone aggregations across the intertidal using a laboratory-based tank experiment to better understand how fixed genotypic and plastic environmental effects contribute to the successful maintenance of this symbiosis in extreme habitats. High intertidal anemones had lower baseline symbiont-to-host cell ratios under control conditions, but their symbionts had higher baseline photosynthetic efficiency compared to low intertidal anemone symbionts. Symbiont communities were identical across all samples, suggesting that shifts in symbiont density and photosynthetic performance could be an acclimatory mechanism to maintain symbiosis in different environments. Despite lower baseline symbiont-to-host cell ratios, high intertidal anemones maintained greater symbiont-to-host cell ratios under heat stress compared with low intertidal anemones, suggesting greater thermal tolerance of high intertidal holobionts. However, the thermal tolerance of clonal anemones acclimatized to different zones was not explained by tidal height alone, indicating additional environmental variables contribute to physiological differences. Host genotype significantly influenced anemone weight, but only explained a minor proportion of variation among symbiotic traits and their response to thermal stress, further implicating environmental history as the primary driver of holobiont tolerance. These results indicate that this symbiosis is highly plastic and may be able to acclimatize to climate change over ecological timescales, defying the convention that symbiotic organisms are more susceptible to environmental stress.

Synthesis of azelaic acid copolyester plasticizers and their application in PVC.

A series of 2-methyl-1,3-propanediol (MPO) modified azelaic acid and hexylene glycol copolyester (PHMAZ) plasticizers with varying contents were synthesized using a direct esterification melt polycondensation method, and their structures were characterized systematically. Analysis using infrared spectroscopy and nuclear magnetic resonance spectroscopy confirmed the synthesis of the designed copolyester structure. Gel permeation chromatography (GPC) tests indicated that the number average molecular weight of each copolyester sample ranged between 2000 and 3000. These copolyesters were used to plasticize polyvinyl chloride (PVC) resin, and the glass transition temperature of the plasticized PVC samples was tested using a differential scanning calorimeter (DSC). Further characterization of the plasticizing effects was conducted using an electronic universal testing machine. The research results showed that as the content of MPO increased, the plasticizing effect of the copolyester initially increased and then decreased. Specifically, the copolyester containing 45% MPO, PHMAZ-45, demonstrated the best plasticizing effect on PVC, with the glass transition temperature of the plasticized PVC system around -35 °C, elongation at break at 908.4%, and a plasticizing efficiency of 254.5%. Additionally, this new type of copolyester plasticizer uses bio-based raw materials, exhibits excellent plasticizing effects, and the preparation process is stable and controllable. It holds promising potential to replace traditional volatile and toxic phthalate esters, presenting significant industrial application value.

Investigation of physico-mechanical, thermal, morphological, and antibacterial effects of bio-based epoxidized soybean oil plasticizer on PLA-ZnO nanocomposites as flexible food packaging

Polylactic acid (PLA) has attracted considerable attention because of its excellent properties compared to petroleum-based materials. However, improving its toughness, crystallization, and functionalities is challenging. Using a laboratory internal batch mixer, we produced unique blended nanocomposites comprising polylactic acid (PLA) as the host matrix, epoxidized soybean oil (ESO) as the plasticizer, and zinc oxide nanoparticles (ZnO NPs) as the reinforcements. The SEM-EDS test showed that neat PLA had a smooth surface, but the PLA-ZnO nanocomposite had rough micrographs and a uniform dispersion state of the nanoparticles. It was also found that adding ESO to the blend nanocomposites created a matrix droplet structure, and the size of the oil domains decreased as the ZnO content increased. All results derived from FTIR, XRD, and DSC tests were consistent with the morphological features in which ZnO NPs acted as the blend’s compatibilizer and heterogeneous nucleating agent. Our team observed that adding ESO decreased the PLA-ZnO nanocomposites’ glass transition temperature (Tg) by an average of 2 °C and increased the crystallization rate. It was also confirmed that the presence of ESO improved the flexibility and reduced the strength of the PLA. The tensile strength was further enhanced by incorporating ZnO into the blend. Adding 5 wt% of ZnO NPs increased the tensile strength of the PLA containing 10 wt% ESO by approximately 3.5 MPa. Furthermore, the tensile modulus was predicted using theoretical models; for example, the Paul model fitted with experimental findings. The addition of ESO increased the overall surface free energy of the nanocomposites. On the other hand, increasing ZnO content resulted in high contact angles and antibacterial properties of the blended nanocomposites. The favorable characteristics of the resulting films emphasized the potential use of these nanocomposite films as a promising choice for food packaging materials.

Two-stage rolling and partial annealing enables heterogeneous structure and strength-ductility enhancement for austenitic stainless steel

Austenitic stainless steels are widely used in civil and defense industries. However, its low yield strength severely limits its fields of application. Under conventional processing routes, uniform grain refinement improves strength but unfortunately sacrifices ductility. In order to achieve the balance of strength and ductility, a new processing route of cold rolling and cryogenic rolling combined with partial annealing was proposed in this work. The results showed that the two-stage rolling and annealing produced dual-phase heterogeneous microstructure containing micron-sized grains (>1 μm), submicron-sized grains (500–1000 nm), and ultra-fine grains (100–500 nm) arranged in lamellar structures. Compared with the single-stage cold rolled and annealed steel, the tensile strength increased to 1.1 GPa, which was slightly higher than the single-stage cryogenic rolled and annealed steel. Furthermore, the elongation was improved to 25 %. The improvement of tensile properties was mainly due to the contribution of persistent hetero-deformation induced (HDI) hardening and twining induced plasticity (TWIP) effect to work hardening. This study not only proposed a simple and effective way to improve the mechanical properties of austenitic stainless steels, but also provided guidance for the design and development of high performance heterostructured materials.

Production of film compositions modified with carboxyl- and hydroxyl-containing compounds based on polyacrylamide

The effect of plasticizers on the physical and mechanical properties of film materials based on polyacrylamide has been studied. It has been established that the introduction of sorbitol, trimethylolpropane and PEG 400 into the composition reduces the tensile strength of film materials. It is shown that the use of plasticizers affects the relative elongation at break and film adhesion.

Early-life exposure to five biodegradable plastics impairs eye development and visually-mediated behavior through disturbing hypothalamus-pituitary-thyroid (HPT) axis in zebrafish larvae

Biodegradable plastics have been commonly developed and applied as an alternative to traditional plastics, which cause environmental plastic pollution. However, biodegradable plastics still present limitations such as stringent degradation conditions and slow degradation rate, and may cause harm to the environment and organisms. Consequently, in this study, zebrafish was used to evaluate the effects of five biodegradable microplastics (MPs), polyglycolic acid (PGA), polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA) and polybutylene adipate terephthalate (PBAT) exposure on the early development, retina morphology, visually-mediated behavior, and thyroid signaling at concentrations of 1 mg/L and 100 mg/L. The results indicated that all MPs induced decreased survival rate, reduced body length, smaller eyes, and smaller heads, affecting the early development of zebrafish larvae. Moreover, the thickness of retinal layers, including inner plexiform layer (IPL), outer nuclear layer (ONL), and retinal ganglion layer (RGL) was decreased, and the expression of key genes related to eye and retinal development was abnormally altered after all MPs exposure. Exposure to PBS and PBAT led to abnormal visually-mediated behavior, indicating likely affected the visual function. All MPs could also cause thyroid system disorders, among which alterations in the thyroid hormone receptors (TRs) genes could affect the retinal development of zebrafish larvae. In summary, biodegradable MPs exhibited eye developmental toxicity and likely impaired the visual function in zebrafish larvae. This provided new evidence for revealing the effects of biodegradable plastics on aquatic organism development and environmental risks to aquatic ecosystems.

Molecular origin of the plasticizing effect difference of glycerol with other polyols on plasticizing polyvinyl alcohol (PVA) as elucidated by solid-state NMR

Glycerol has been proved to be an effective plasticizer for polyvinyl alcohol (PVA), which can significantly increase PVA’s processability and ductility, whose molecular origin remains unclear. In current study, the physical structure and chain dynamics of polyol plasticized PVA were studied in detail, including ethylene glycol, glycerol, erythritol, xylitol, and sorbitol under the same addition level. The glycerol plasticized PVA exhibits the most significant reduction in Young’s modulus, enhanced superior toughness, and the lowest melting temperature (195 °C) as compared with other polyols. The molecular mechanism was elucidated through comprehensive analysis, with a particular focus on solid state NMR (SS NMR) results. The physical structure was first elucidated by the Small Angle X-ray Scattering (SAXS) and Wide Angle X-ray Scattering (WAXS). The crystallinity of the glycerol plasticized PVA was the lowest 29 % by WAXS and the thickness of the amorphous layer was the largest 7.76 nm by SAXS among different plasticized PVA films. This suggests the significant influence of glycerol on structure change of PVA. The molecular dynamics information was further accessed by Low Field Nuclear Magnetic Resonance (LF NMR), where two key features are obtained: i) Different dynamics dimensionality. The 1H spin diffusion NMR was used to check the dimensionality from the aspect of chain dynamics. Compared with other plasticizers, LF NMR result shows that glycerol plasticized PVA has a two-dimensional (2D) structure; ii) Chain dynamics heterogeneity in the interphase. With respect to the chain dynamics heterogeneity in the interphase, the glycerol plasticized PVA shows the most heterogeneous dynamics, with the lowest ratio of the rigid amorphous fraction (RAF) of 0.507 in the interphase. Current study provides a versatile analytical strategy to quantify the plasticizing effect.

Understanding plasticity in multiphase quenching & partitioning steels: Insights from crystal plasticity with stress state-dependent martensitic transformation

This study develops a novel crystal plasticity (CP) model incorporating deformation-induced martensitic transformation (DIMT) and transformation-induced plasticity (TRIP) effect to predict the complex interplay between microstructural evolution and mechanical behavior in a third-generation advanced high-strength steel QP980. This model introduces phenomenological theory of martensite crystallography (PTMC) based TRIP theory and DIMT kinetics grounded on nucleation-controlled phenomenon. Notably, the DIMT model is improved by utilizing a geometric approach for calculating shear band intersections. A virtual multiphase representative volume element (RVE) based on the Voronoi tessellation is generated for the QP980 steel, which comprises ferrite, martensite, and retained austenite (RA). The study highlights how phase transformation affects mechanical properties, notably the strengthening from transformed martensite and the mechanical alterations in RA due to the TRIP effect. The DIMT kinetics dependent on stress states such as uniaxial tension (UT), uniaxial compression (UC), plane strain tension (PST), and equi-biaxial tension (EBT) are analyzed using the developed model. The role of microstructural surroundings on martensitic transformation is also examined. Furthermore, analysis under biaxial loading angles using the model reveals an asymmetric yield surface, with more pronounced changes in yield stress in the tensile region due to accelerated transformation behaviors, as opposed to the more gradual transformations in the compressive region. This study provides valuable insights into the deformation mechanisms of the third-generation advanced high-strength steels including relationship between plastic anisotropy, transformation kinetics, and microstructural evolution.

Plasticization mechanism of biobased plasticizers comprising polyethylene glycol diglycidyl ether-butyl citrate with both long and short chains on poly(lactic acid)

Polylactic acid (PLA), a biodegradable polymer with low flexibility, is commonly plasticized with small molecules like tributyl citrate (TBC) for film production. However, these plasticizers, which lack chemical bonds or strong intermolecular interactions with the matrix, tend to migrate to the film surface over time. Their inclusion often compromises material strength for flexibility, increasing elongation at break but reducing tensile strength. In this research, by combining citric acid with n-butanol (B) and poly(ethylene glycol) diglycidyl ether (E), we synthesized three plasticizers, namely TE3, TE2B1, and TE1B2, to enhance the flexibility of PLA. TE2B1 and TE1B2 are equipped with butyl ester groups that offer effective plasticizing effects. Additionally, the incorporation of long-chain alkyl featuring epoxy groups can boost the interaction with PLA. The results showed that the epoxy groups of the long-chain alkyl plasticizers can improve the elongation at break without compromising tensile strength significantly. The migration of plasticizer from PLA matrix can be reduced by strong interactions like chemical bonds, entanglements, and hydrogen bonding with PLA. TE1B2 demonstrated the best plasticizing effect. Adding 15 portions of TE1B2 and TBC separately increased PLA's elongation at break to 304 % and 242 %, with tensile strengths of 36.1 MPa and 22.3 MPa, respectively.

Temperature and strain rate-dependent compression properties of 3D-printed PLA: an experimental and modeling analysis

PurposeThis study aims to investigate the compression characteristics of the 3D-printed polylactic acid (PLA) samples at temperatures below the glass transition temperature (Tg) with varying strain rates and develop a thermo-mechanical viscoplastic constitutive model to predict the finite strain compression response using a single set of material parameters. Also, the micro-mechanical damage processes are linked to the global stress–strain response at varied strain rates and temperatures through scanning electron microscopy (SEM).Design/methodology/approachTg of PLA was determined using a dynamic mechanical analyzer. Compression experiments were conducted at strain rates of 2 × 10–3/s and 2 × 10–2/s at 25°C, 40°C and 50°C. The failure mechanisms were examined using SEM. A finite strain thermo-mechanical viscoplastic constitutive model was developed to analyze the deformations at the considered strain rates and temperatures.FindingsTg of PLA was determined as 55°C. While the yield and post-yield stresses drop with increasing temperature, their trend reverses with an increased strain rate. SEM imaging indicated plasticizing effects at higher temperatures, while filament fragmentation and twisting at higher strain rates were identified as the dominant failure mechanisms. Using a non-linear regression analysis to predict the experimental data, an overall R2 value of 0.98 was achieved between experimental and model prediction, implying the robustness of the model’s calibration.Originality/valueIn this study, a viscoplastic constitutive model was developed that considers the combined effect of temperature and strain rate for FDM-printed PLA experiencing extensive compression. Using appropriate temperature-dependent modulus and flow rate properties, a single set of model parameters predicted the rise in the gap between yield stress and degree of softening as strain rates and temperatures increased.

The Increase in the Plasticity of Microcrystalline Cellulose Spheres' When Loaded with a Plasticizer.

Compaction pressure can induce an undesirable solid-state polymorphic transition in drugs, fragmentation, loss of coated pellet integrity, and the decreased viability and vitality of microorganisms. Thus, the excipients with increased plasticity can be considered as an option to decrease the undesirable effects of compaction pressure. This study aims to increase the plasticity (to reduce the mean yield pressure; Py) of dried microcrystalline cellulose (MCC) by loading it with a specially selected plasticizer. Diethyl citrate (DEC), water, and glycerol were the considered plasticizers. Computation of solubility parameters was used to predict the miscibility of MCC with plasticizers (possible plasticization effect). Plasticizer-loaded MCC spheres with 5.0 wt.% of water, 5.2 wt.% of DEC, and 4.2 wt.% glycerol were obtained via the solvent method, followed by solvent evaporation. Plasticizer-loaded formulations were characterised by TGA, DSC, pXRD, FTIR, pressure-displacement profiles, and in-die Heckel plots. Py was derived from the in-die Heckel analysis and was used as a plasticity parameter. In comparison with non-plasticized MCC (Py = 136.5 MPa), the plasticity of plasticizer-loaded formulations increased (and Py decreased) from DEC (124.7 MPa) to water (106.6 MPa) and glycerol (99.9 MPa), and that was in full accordance with the predicted miscibility likeliness order based on solubility parameters. Therefore, water and glycerol were able to decrease the Py of non-plasticized MCC spheres by 16.3 and 30.0%, respectively. This feasibility study showed the possibility of modifying the plasticity of MCC by loading it with a specially selected plasticizer.

Epoxidized Soybean Oil Toughened Poly(lactic acid)/Lignin-g-Poly(lauryl methacrylate) Bio-Composite Films with Potential Food Packaging Application.

The application of lignin as a filler for poly (lactic acid) (PLA) is limited by their poor interfacial adhesion. To address this challenge, lignin-graft-poly(lauryl methacrylate) (LG-g-PLMA) was first blended with poly (lactic acid), and then epoxidized soybean oil (ESO) was also added to prepare PLA/LG-g-PLMA/ESO composite, which was subsequently hot pressed to prepare the composite films. The effect of ESO as a plasticizer on the thermal, mechanical, and rheological properties, as well as the fracture surface morphology of the PLA/LG-g-PLMA composite films, were investigated. It was found that the compatibility and toughness of the composites were improved by the addition of ESO. The elongation at break of the composites with an ESO content of 5 phr was increased from 5.6% to 104.6%, and the tensile toughness was increased from 4.1 MJ/m3 to 44.7 MJ/m3, as compared with the PLA/LG-g-PLMA composite without ESO addition. The toughening effect of ESO on composites is generally attributed to the plasticization effect of ESO, and the interaction between the epoxy groups of ESO and the terminal carboxyl groups of PLA. Furthermore, PLA/LG-g-PLMA/ESO composite films exhibited excellent UV barrier properties and an overall migration value below the permitted limit (10 mg/dm2), indicating that the thus-prepared biocomposite films might potentially be applied to environmentally friendly food packaging.

On the role of surface stress in environment-assisted fracture

Abstract Environment effects in plasticity and fracture of metals, well studied for several decades, still pose many unanswered questions. A micro-mechanics explanation of how dislocation activity is influenced by the material surface state, that can answer these questions, has been elusive. We build on a recently discovered effect in metal cutting – organic monolayer embrittlement (OME) – wherein metal surfaces are rendered brittle by long-chain organic adsorbates, to explore how material state variables influence surface plasticity and fracture. In particular, cutting experiments with Al containing Self Assembled Monolayers (SAMs), show that the OME is controlled by surface stress (f) induced by the adsorbates. This is contrary to many instances of environment-assisted fracture which are usually attributed to surface energy changes, and wherein f is largely ignored. Other contributions include (a) a cantilever technique to measure surface stress, (b) demonstration of strong effect of SAM molecule chain length on f, (c) characterization of how dislocation activity at crack-tips is affected by adsorbate-induced f, and (d) large improvements in machining processes enabled by controlled environment-assisted fracture. We make the case that surface stress, due to adsorbates, likely influences all environmentally assisted cracking (EAC) phenomena, warranting a revisit of extant models of EAC.

Effect of Plasticizer Type on Polymer Inclusion Membranes Properties and Performance for Zinc Separation

AbstractThe goal of the present study is to evaluate the effect of plasticizer in PIMs properties and performance for zinc separation. Membranes were prepared by casting a solution containing poly (vinyl chloride) (PVC) as base polymer, di (2‐ethylhexyl) phosphoric acid (D2EHPA) as carrier, and 2‐nitrophenyl octyl ether (NPOE) or tris (2‐butoxyethyl) phosphate (TBEP) as plasticizers. The newly developed PIMs transported practically all ZnII ions from a feed phase at pH 5 to a 1 M H2SO4 stripping phase. The results showed that the transport flux and its efficiency depend on the chemical nature of the plasticizer. It can be perceived that NPOE (with dielectric constant of 23.1) produced the highest transport flux of zinc (J0=1.62±0.05 10−5 mol m−2 s−1). The single ion transport of zinc was significantly higher than the binary and ternary mixtures. In ternary solution, the transport efficiency for metal ions was in the order of ZnII>CuII>NiII. The transport efficiency of the PVC/NPOE/D2EHPA membrane remained constant until the seventh use. The findings of this work will allow the invention of advanced separation technology ensuring the sustainability of metal resources.

Effects of magnetic intensity on the machining quality and tool damage in nickel-based superalloys subjected to magnetic-assisted cutting

Nickel-based superalloys are widely used in engine components due to their excellent high-temperature strength. However, their low plasticity and low thermal conductivity pose significant challenges in machining, leading to poor quality of machined parts and severe tool wear. Magnetic-assisted machining has received considerable attention as a clean and effective machining method, but its application to nickel-based superalloys is rarely reported, necessitating further exploration of its potential. This study focuses on GH4169 alloy and explores the effects of magnetic-assisted cutting (MAC) with varying intensities on the machining quality and tool wear. The experimental results indicate that the introduction of a magnetic field improves the machining quality by reducing tool wear and built-up edge adhesion. Additionally, both the plasticity and thermal conductivity of GH4169 alloy are improved under the effect of magnetic field, resulting in an 11.4 % decrease in cutting temperature. However, when the magnetic intensity ranges from 0.03 T to 0.12 T, secondary serration of the chip edges manifests, resulting in notch wear on the tool nose and a deterioration of surface quality. This secondary serration is attributed to the combined effect of tool nose radius and material plasticity under the magnetic field. As the magnetic field intensity increases further, the secondary serration gradually diminishes, and the surface roughness can be reduced by 26.5 % compared to traditional cutting. This study analyzed the relationship between machined surface, tool wear, chip morphology and magnetic field, and revealed the reasons for the differences in machining quality at different magnetic field intensities. These findings provide more possibilities for future applications of magnetic-assisted cutting to improve the machining quality of nickel-based superalloys and other difficult-to-machine metals.

Microstructure evolution and twinning-induced plasticity (TWIP) in hcp rare-earth high- and medium-entropy alloys (HEAs and MEAs) due to tensile deformation

The microstructure evolution due to the tensile deformation of the equiatomic quinary high-entropy alloy Ho-Dy-Y-Gd-Tb (HEA-Fb) is assessed. HEA-Fb has extraordinarily similar alloying elements. It is one of the few hexagonal-close-packed single-phase representatives of HEA. HEA-Fb is compared to the equiatomic quaternary medium-entropy alloy (MEA) Ho-Dy-Gd-Tb with no Y (4-Y). For a hexagonal HEA, in contrast to the cubic HEA, little information on plastic deformation and underlying mechanisms is available. A detailed study using electron microscopy-based multi-scale characterization (SEM, S/TEM, and STEM-EDS) explains significant differences between the ductile behavior of the quaternary MEA 4-Y and the brittle behavior of the quinary HEA-Fb at room temperature. Twinning during plastic deformation is decisive for ductility, which challenges the widely discussed high-entropy effect on the mechanical behavior of the HEA. For the quaternary MEA 4-Y, a twinning-induced plasticity effect is found. In the latter, oxidized twins are present in the undeformed state. In both alloys, the twin orientations are indexed as [2¯201], while the matrices have the perpendicular [112¯0] orientation. Additionally, the analysis of twin structures confirms the importance of twin boundaries as obstacles for dislocations and stacking fault mobilities. The results are discussed in the context of the existing knowledge gaps in the field of hexagonal MEAs and HEAs.

Synergistic improvement of strength and ductility by high magnetic field assisted intercritical annealing in lightweight medium Mn steel

The microstructures and mechanical properties of lightweight medium Mn steels were studied by high magnetic field (HMF) assisted intercritical annealing process (HMF-IA). The results show that the volume fraction of retained austenite increased and reached the maximum value of 56.2 % when the magnetic flux density (MFD) was 10 T at first and then decreased with the increase of MFD. The application of 10 T HMF promoted the diffusion ability of carbon atoms into austenite by magnetic stress-driven dislocation movement and increased the volume fraction and grain size of austenite. HMF also played a critical role in dislocation movement and element partitioning during the IA process. Due to the wide range of bimodal size distribution of austenite after the HMF-IA process, stronger transformation induced plasticity effect and twin induced plasticity effect happened in the process of plastic deformation. For the sample annealed under 10 T, comparing with the sample annealed without HMF, the product of strength and elongation value increased from 45.7 GPa·% to 55.1 GPa·%. Additionally, it also kept a persistent high strain hardening. The present study provides a new understanding of the role of HMF in adjusting the relationship between microstructure and mechanical properties during the annealing process and opens up a new path for designing industrial medium Mn steel with low cost, high performance and simple process.