Changes In Surface Microstructure Research Articles

Molecular dynamics study on wetting behavior of aluminum plates with different surface energies by microstructure difference

Wettability is the main factor that affects the self-cleaning and corrosion resistance of metal surfaces. The main factor that affects wettability is the change of surface microstructure and surface energy of metal material. When modifying metals, it is necessary to master their wetting behavior to obtain the required performance surface. In this paper, the wetting behavior of liquid droplets on smooth, square, papillary and nail-shaped surfaces with different surface energies was studied systematically by molecular dynamics simulation. The results show that the solid–liquid interaction factor is negatively correlated with the surface contact angle of aluminum plate. When the solid–liquid interaction factor is greater than the droplet potential energy parameter, the nail-shaped surface has the largest solid–liquid contact area and droplet centroid displacement rate due to its large roughness, and the surface hydrophilicity is the best; When the solid–liquid interaction factor is close to the droplet potential energy parameter, the nail-shaped surface has the smallest solid–liquid contact area and droplet centroid displacement rate due to its large roughness, and realizes the transition from neutral to hydrophobic; When the solid–liquid interaction factor is less than the droplet potential energy parameter, the papillary surface has the smallest solid–liquid contact area and droplet centroid displacement rate due to its small solid–liquid area fraction, thus realizing the transition from hydrophobicity to superhydrophobicity. The simulation results of this study are consistent with the classical theoretical calculation and experimental results, which reveals the interaction between metal surface wettability and surface energy and surface morphology.

Exploring the Effects of Laser Surface Modification on AISI 301LN Steel: A Micro-Mechanical Study

This article investigates the surface hardening capability of a metastable austenitic TRansformation Induced Plasticity (TRIP) stainless steel, particularly on AISI 301LN, by laser texturing. This technology produces microstructural surface changes in terms of both phase transformation and grain size modification and, as a direct consequence, the laser influences the surface characteristics, mainly hardness and roughness. In this sense, the key parameters (laser power, scanning speed and position of the focal length) were investigated by using a Design of Experiments (DoE) in detail to better understand the correlation between texturing parameters, microstructural and mechanical changes, always at the superficial level. From all the aforementioned information, the results show that the maximum surface hardening is obtained by increasing the laser power and decreasing the scanning speed. Furthermore, by reducing the focal distance, the depth of the microstructural evolution layer is more significant, while the width is less affected. Finally, a suitable model was developed to correlate the processing parameters here investigated with the resulting surface integrity, in terms of mechanical properties, by means of a regression equation.

The effect of polished surface microstructure of ceramic electrolyte on solid-state sodium metal batteries

Highly stable Na anode/solid-state electrolyte (SSE) interface is vital for engineering robust solid-state sodium metal battery (SSMB). To ensure the flatness and remove the surface impurities of SSE, ceramic SSE pellets commonly require to be polished. However, there are lack of standardized instructions about the polish procedure even though researchers have realized that the properties of Na/SSE interface could be influenced dramatically by the surface microstructure of SSE pellet. In this work, the Na3.3Zr1.7Pr0.3Si2PO12 SSE pellets were polished transversely and longitudinally by sandpaper with various mesh sizes on purpose for engineering Na/SSE interfaces. It is discovered that the compatibility and wettability of Na on SSE pellets could be tuned by polish procedure due to the resultant variation of roughness, contact area and ravines. By optimizing surface microstructure of SSE pellets through polishing, the assembled symmetrical battery delivers the highest critical current density of 0.55 mA cm−2 and the lowest interface impedance (11.8 Ω cm2) at room temperature, enabling the stably cycling for 5000 h at 0.1 mA cm−2. This work sheds light on the strong correlations between polish-induced surface-microstructural changes of SSE and interface stability of Na/SSE, providing a rational reference for SSE polishing when assembling SSMB.

Surface treatment of inorganic modifier for improving carbonation resistance of geopolymers

Geopolymer (GP) is a low-carbon binder with the potential to replace Portland cement in reinforced concrete, however, the risk of corrosion to reinforced steel bars due to its low carbonation resistance must be addressed. This study proposed the use of an inorganic surface modifier, sodium aluminate solution (AN), to improve the carbonation resistance of GP. The effects of AN surface treatment on carbonation depths were investigated for GP mortars using fly ash (FA), ground granulated blast furnace slag (BFS), or their blend as active fillers. Rational AN surface treatment conditions and microstructural changes of treated GPs were also discussed. The obtained results show that AN surface treatment can significantly reduce carbonation rates of FA/BFS blend-based GP, and largely delay the onset of neutralization of heat-cured GP through the reduction of cracks and the formation of Na-gmelinite and gismondine, which refine the surface layer of GP. The surface modification using 40 wt%-AN solution reduced carbonation rate coefficient by about 70% for the FA/BFS blend-based GP cured at 80 ℃, and by above 30% for that cured at 20℃. The larger the FA blending ratio or the smaller the liquid-active filler ratio, the greater the improvement in carbonation resistance of FA/BFS blend-based GPs, caused by the AN surface modification. For the ambient-cured GP, repeated surface treatment is preferred, while for the heat-cured GP, once treatment is enough, and seal curing after the AN surface treatment is recommended regardless of the curing method.

Sodium salt surface interactions affect single particle combustion behavior of biomass, coal, and their chars

Sodium salt additions provide an effective route for tuning the combustion behavior of solid fuels. The salt-fuel surface interactions play a key role in combustion, as demonstrated by low heating rate experiments. High heating rate single particle studies have not investigated the effect of surface interactions and microstructural changes for sodium salt-treated fuels. In this work, the effect of three different sodium salt treatments were investigated on the single particle combustion characteristics of two distinct solid fuels and their corresponding chars. This approach probed the influence of microstructural changes and the formation of oxidation-resistive functional groups during high heating rate combustion. The separate characterization of biomass, coal, and their respective chars aimed at identifying the effect of sodium during different stages of combustion. The investigation encompassed Tunçbilek lignite (TL), olive residue (OR), and their fast pyrolysis chars (TLc and ORc) obtained from a wire mesh reactor at 600 °C. Both pristine and char particles were treated with Na2CO3, NaOH, and NaAlO2 to investigate the catalytic/inhibiting effects at different stages of combustion, namely, ignition, volatile combustion, and char combustion. All samples were burned as single particles at a high heating rate, WMR (1600 °C s−1). Treated OR samples provided earlier ignition reaching ∼ 0.4 s for OR-OH and shorter char combustion times around ∼ 2.8 s mg−1 for OR-CO3. On the contrary, treated TL samples depicted slightly higher ignition delay (3.0 s for TL-OH) and prolonged char combustion (11.2 s mg−1 for TL-OH) compared to TL (2.3 s, 8.2 s mg−1). Treated TLc samples also exhibited higher ignition delay due to the hygroscopic behavior of the sodium salts, which is more pronounced in TLc-OH (5.5 s). All treated chars exhibited shorter char combustion times except TLc-OH. Overall, sodium salt additions improved characteristic combustion times of biomass and chars while inhibiting those of lignites. The inhibitive effect of sodium salts on treated OR and ORc samples was more pronounced for TGA experiments due to the alkali interaction with the lignocellulosic component and a prolonged heating-up period. The findings demonstrate the importance of high heating rate characterization to accurately understand the sodium salt additions on combustion performance.

Electrochemical surface rehydrogenation of boron-doped diamond electrodes after electrochemical polishing

Non-diamond carbon impurity and surface roughness are features that can affect the response of boron-doped diamond (BDD) electrodes. Herein, we report on the electropolishing of BDD electrodes carried out in the presence of acetic and sulfuric acid for different times (1, 2, and 4 h). The wet electrochemical treatment smooths the polycrystalline diamond surface and reduces the non-diamond sp2 carbon impurity content while increasing the surface oxygen content. Changes in surface texture and microstructure were revealed by atomic force microscopy, Raman spectroscopy, and cyclic voltammetry. Subsequently, the surface oxygen content was reduced by increasingly severe cathodic pretreatments (CPTs). This was revealed by changes in the voltametric response for the [Fe(CN)6]3−/4– and ascorbic acid (AA) redox systems, as both exhibit electron transfer kinetics sensitive to the level of oxidation of the BDD surface. For [Fe(CN)6]3−/4–, greater ∆Ep values were obtained for the electropolished (EP-BDD) electrodes, as compared to the as received (AR-BDD) electrode. However, after CPTs the EP-BDD electrodes exhibited smaller ∆Ep values (∼60 mV), which indicate significantly improved electrochemical reversibility and faster electron-transfer kinetics caused by the decreased level of surface oxidation (greater hydrogenation). The increased surface oxygen content brought on by the electropolishing process had also a significant effect on the AA oxidation peak potential (Eap), making it at least ∼140 mV more positive than that for the AR–BDD electrode. However, after CPTs the Eap values for the EP–BDD electrodes became at least ∼0.1 V less positive than that for the AR–BDD electrode, indicating that the surface of the EP-BDD electrodes possesses less surface carbon‑oxygen functional groups (i.e., it is more hydrogenated). The combination of electropolishing and cathodic pretreatment is a way to process the BDD electrode surface to create a smoother, low oxygen surface in much the same way as a hydrogen plasma treatment does.

Mechanical properties of stainless steel by using high temperature microhardness tester

In the aeronautical field, materials are used in severe environmental conditions (temperature, atmosphere), particularly for engine applications. In order to qualify new alloys compositions, ONERA is developing micromechanical characterization means to carry out indentation tests from room temperature up to 700 °C under conditions close to operating conditions. This method presents the interest of performing tests faster than classical mechanical tests like tensile or bending tests under severe conditions and with small amounts of materials. In order to carry out screening tests, a 316L stainless steel is studied and the evolution of hot Vickers hardness properties and yield stress versus temperature are presented. By increasing the applied load from 0.1 to 20 N, we show that we can neglect surface microstructural changes or possible contamination of the sample surface by oxidation. We show that from 0.5 N, the hardness measurement is independent of load on 316L stainless steel. By using Tabor’s law to express the mechanical resistance, we show that the hardness decreases by 50% when the test temperature goes from 20 to 700 °C, which is close to the supplier’s values. A discussion on the use of indentation to determine mechanical resistance and the limitations of this technique is presented. In perspective, these measurements could be carried out at 1000 °C and on many different materials such as layers, coatings, composite materials, brazing cords or additive manufacturing materials.

Relation between Mechanical Hardening and Nitrogen Profile of PBII Nitrided Titanium Alloy.

Surface treatments of Ti-6Al-4V alloys are of utmost importance for biomedical applications since they allow for tribological gain. Here, Ti-6Al-4V disks have been PBII nitrided at either 500, 600, 700 and 800 °C. A set of techniques (XRD, SEM-EDS, EBSD and GDOES) was used to characterize the surface microstructural and chemical changes. Nanoindentation was used to assess the induced changes in terms of mechanical properties. Two types of nitrided domains are revealed. Starting from the surface, a nitride bilayer composed of δ-TiN/ϵ-Ti2N with enhanced surface resistance is supported by an α-Ti(N) solid solution formed at depth. Hardness values peak at 12-14 GPa at the surface, which is almost twice as large as the bulk value (about 7 GPa). For the moderate temperatures used here, a deep (10-15 µm) and strong hardness (14 GPa) enhancement together with a smooth gradient can be achieved.

Ice resistance of hydrophobic fluoropolymerized nanostructured alumina films for antireflective coatings

The functionality and durability of nanostructured alumina coatings exposed to atmospheric icing has been assessed to probe their usability in practical applications and to estimate the need for further development of the coatings. In particular, the changes in surface microstructure and in optical performance as well as in the wetting characteristics of the surfaces are reported. Without a hydrophobicity treatment the alumina nanostructures are superhydrophilic and do not endure large environmental changes. Hydrophobicity treated fluoropolymerized nanostructured alumina provides characteristics with partial anti-icing capabilities, enhanced durability, and excellent transmission levels of >95%, but the performance degrades in cyclic icing/de-icing. However, the hydrophobic nanostructured alumina outperforms both the nanostructured and planar alumina coatings and possesses increased durability and stability even under harsh conditions, such as the atmospheric icing. This indicates a clear need to use a hydrophobicity treatment for the nanostructured alumina antireflection coatings to be used in any environments. Therefore, its utilization in applications where little or occasional exposure to icing or other humidity and temperature changes is favorable over standard planar coatings. Further process optimization of the hydrophobicity treatment is still needed for better durability for cyclical icing exposure.

Effect of anisotropic grain boundaries on the surface blistering of tungsten induced by deuterium plasma exposure

The effect of anisotropic grain boundaries on the surface microstructure changes and deuterium retention behavior in tungsten under deuterium plasma irradiation were studied. The samples named as NDW and RDW were cut from RD × TD plane and TD × ND plane of a rolled W plate (ND: normal direction, RD: rolling direction, TD: transverse direction), respectively. The results suggest that both surface morphology and deuterium retention in the RDW samples are suppressed compared to that of NDW samples for 1 h and 25 h deuterium irradiation. For 1 h exposure, the total deuterium retention in the NDW samples is about 1.6 times as much as that of RDW. However, as the exposure time increased to 25 h, the total deuterium retention in the NDW sample is two times the height of RDW sample. The experimental results show that the special grain structure of RDW can alleviate the surface morphology changes and decrease the deuterium retention in tungsten, which is interpreted by the lateral stress model of blistering.

Effects of the SiO2 underlayer on magnetic properties of the Pr-Fe-B thin film

Si3N4/Pr-Fe-B/SiO2 thin films were deposited by magnetron sputtering on Si (100) substrate with in-situ annealing at 650 °C. The magnetic properties of these thin films showed significant changes at the various thicknesses of the SiO2 underlayer. This resulted from various growth and orientations of the Pr2Fe14B hard-magnetic phase, and a new Fe3Si underlayer was differently formed at the interface of the Pr-Fe-B layer/SiO2 underlayer. It also led to changes in surface morphology and microstructure of thin films. Coercivity showed a considerable increment at the 75 nm thickness. A better perpendicular anisotropy was found at 20 and 50 nm thicknesses, although coercivities were lower at these thicknesses. Oxygen composition showed an insignificant effect on the magnetic properties of Pr-Fe-B thin film.

Effects of Different Scan Speeds on Microstructural and Corrosion Properties of Additively Manufactured HSLA Steels in 3.5% NaCl Solution

In automotive applications, high-strength low alloy (HSLA) steels are providing enhanced material properties, due to the high yield strength, less fragility, and lower weight, which also promotes lower fuel consumption. HSLA steels contain a small amount of carbon (under 0.2%) and also contain small amounts of alloying elements such as copper, nickel, niobium, vanadium, chromium, molybdenum and zirconium. This eliminates the toughness reducing effect of a pearlitic volume fraction, yet maintains and increases the material's strength by refining the grain size. Therefore, HSLA steels are used for structures intended to handle large amounts of stress or that need a good strength-to-weight ratio. Traditional manufacturing methods for steel (e.g., blast furnace or electric arc furnace methods) fail to provide the necessary optimization for best output in terms of performance and application. The quality of molten steel is greatly affected by scrap steel. The smelting period is longer, and the power consumption is large. In addition, these processes allow more impurities into the molten steel, which compromises the quality of the final product. However, additive manufacturing (AM) can can be used to fabricate HSLA steel components without these drawbacks. In addition, AM can provide a relatively faster process with low manufacturing costs, in comparison with traditional processing methods. Although AM has several benefits, studies shows that AM processes can result in HSLA steels with microstructural defects, such as non-homogeneity, internal cavities, inclusions, and impurities. Consequently, these microstructural features have a significant affect on the corrosion properties of AM parts as corrosion tends to initiate in defective regions. The AM processing parameters directly impact the microstructure of the fabricated part. Hence, it is important to understand the relationship between the AM processing parameters on resulting microstructural features. The present work evaluated the electrochemical corrosion properties of HSLA steels fabricated by AM via selective laser melting (SLM) under different processing conditions. The goal of the work was to investigate the role of microstructure on electrochemical corrosion in high-strength low alloy steels due to SLM processing conditions.Two types of HSLA steels, Fe 367 and Fe 398, were fabricated by AM via (SLM). Fe 398 differs from Fe 367 as it contains molybdenum and nickel. Each type was fabricated at a laser power of 100W, and scan speed of 600, 800, 100 and 1200 mm/s. The samples were exposed to 3.5% NaCl for 15 days, individually. To acquire the electrochemical corrosion data and to perform analysis, a Gamry reference 600 potentiostat/galvanostat was used. The electrochemical data were obtained by collecting the impedance spectra, and measuring the polarization resistance every 5 days. On day 15, cyclic polarization data was collected for each sample. These measurements helped to identify the localized corrosion as well as provide detailed information about the corrosion properties, such as passive layer growth, initiation and secession of pitting, and corrosion rate. The topography of the materials was observed by SEM before and after the corrosion tests. Energy Dispersive Spectroscopy (EDS) was performed on the samples to identify the chemical elements. The surface roughness was observed through confocal microscope.The Confocal and SEM images showed the change in surface microstructure and topographical properties of the samples before and after the corrosion testing. The difference in laser power and scan speed affected the microstructure and corrosion properties of the materials. As the samples were manufactured at same laser power, the scan speed was responsible for different topographical and corrosion behavior. Samples manufactured at lower scan speed showed less flaws on the surface of the materials than the samples manufactured at higher scan speed. Therefore, both Fe 398 and Fe 367 showed better surface topography at 600 mm/s and 800 mm/s. They also demonstrated significantly lower corrosion rate than the other samples. EDS identified chemical oxides and chlorides which were formed during the corrosion test. Overall, this work demonstrated that Fe 398 shows better microstructural and corrosion properties than Fe 367 at lower scan speed.

Regulation Mechanism of Trivalent Cations on Friction Coefficient of a Poly(Vinylphosphonic Acid) (PVPA) Superlubricity System

The application range of superlubricity systems can be extended effectively by realizing an adjustable friction coefficient. In this study, a stable poly(vinylphosphonic acid) (PVPA) superlubricity system was developed using sodium chloride (NaCl) solution as the lubricant. A sudden increase in the friction coefficient occurred when a trivalent salt solution was introduced to the base lubricant during the friction process. The changes in surface microstructure and interfacial molecular behavior induced by trivalent cations were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and molecular dynamics simulation. The regulation mechanism of trivalent cations with respect to the friction coefficient of the PVPA superlubricity system was explored. Although La3+ and Fe3+ in solutions exist in two forms (La3+ and Fe(OH)3), both can destroy the stable coating structure through a bridging effect, resulting in a sudden increase in the friction coefficient. The ability of various cations to attract the surrounding water molecules is an important reason for the varying degree of change of the friction coefficient. In addition, the degree of sudden increase in the friction coefficient is dependent on the concentration of trivalent cations. There is an extreme concentration at which the maximum sudden increase degree in friction coefficient can be obtained. This study provides insights into the realization of oil-based superlubricity through interface regulation.

Preparation, characterizations, dielectric properties and nonlinear behavior of (Na+1/3Ca2+1/3Yb3+1/3)Cu3Ti4O12 ceramics

We present the investigation of phase formation, microstructural, dielectric properties and nonlinear behaviors of (Na1/3Ca1/3Yb1/3)Cu3Ti4O12 ceramics prepared by a modified sol-gel method under various sintering conditions. According to the Rietveld refinement analysis, the main phase CaCu3Ti4O12-like (Na1/3Ca1/3Yb1/3)Cu3Ti4O12 structure with a lattice constant of ≈7.384 Å was observed in the studied samples. The surface microstructural changes for the ceramics at different conditions were examined by scanning electron microscopy. The dielectric response and nonlinear behaviors of the specimens were methodically explored. At 1 kHz, a high dielectric constant of 5.49 × 103 with a low dielectric loss tangent ≈0.075 was successfully achieved. The sintered (Na1/3Ca1/3Yb1/3)Cu3Ti4O12 ceramics exhibited good nonlinear behavior. The interfacial polarization at the grain boundaries based on the internal barrier layer capacitor structure could explain the dielectric behavior of the studied specimens. From the results of the X-ray photoelectron spectroscopy (XPS) analysis, the presence of Cu+, Cu2+, and Ti3+ ions might be the major cause of the n-type semiconductor nature inside the grains.

The Influence of the Surface Micro-structure Change on the Stainless Steel Effective Thermal Diffusivity

The Influence of the Surface Micro-structure Change on the Stainless Steel Effective Thermal Diffusivity

Using sol-gel deposition of nanosilica to enhance interface bonding between sisal fiber and ultra-high performance concrete

A new idea of using sol-gel method deposition of nanosilica on sisal fibers for improving the interface bonding with ultra-high performance concrete (UHPC) was suggested in this study. The change in surface microstructure, chemical groups, surface roughness, thermal degradation process, phase composition, and tensile strength of modified sisal fiber were characterized. Moreover, the fiber modification on early hydration, bond performance, mechanical performance, and autogenous shrinkage of UHPC was further explored. The results showed that nanosilica was successfully coated on sisal fibers, and these nanosilica particles accelerate the early hydration of mixtures. The bond strength (pullout energy) was increased by 28.0% (40.8%) by nanosilica deposition. Consequently, the flexural strength and toughness of UHPC incorporating nanosilica-modified sisal fibers were 9.8% and 40.5% higher than those of untreated sisal fibers reinforced UHPC. Furthermore, the shrinkage-reducing effect of sisal fibers after deposition of nanosilica was increased by 11.5% compared with the untreated fibers. Therefore, nanosilica deposition is a promising method for enhancing the bond performance between plant fiber and UHPC matrix.

Novel polymer nanocomposite based on polypyrrole and ZrO2 reinforced BN nanosheets: Prospective utilization as implant coatings for TiNbZr bio-implant alloy

Providing Ti-alloy with tunable corrosion resistance and biocompatible characteristics can yield a preferred implant surface to aid an optimistic bone healing. An electrochemically synthesized nanocomposite coating based on polypyrrole (PPy) and ZrO2 decorated boron nitride (ZrO2-BN) nanosheets was explored as polymeric bioactive coatings for TiNbZr alloy in orthopedic applications. In vitro corrosion resistance and biocompatibility of PPy/ZrO2-BN nanocomposite coatings were systematically inspected by correlating them with the structural and surface microstructural changes observed in the prepared coatings. The positive role of ZrO2 addition on BN nanosheets was evaluated using surface and structural analyses in terms of its improvement on homogeneous dispersion and interfacial interaction with the host PPy matrix. Bio-corrosion test results in Hank's solution confirmed that PPy coatings with the inclusion of 15 mg/L of ZrO2-BN provided the best surface protective performance against corrosion among the investigated specimens. In vitro biocompatibility assay was performed on MG63 osteosarcoma cell lines and the obtained results confirmed the beneficial role of ZrO2-BN nanosheets in improving the bioactivity of PPy coatings on the Ti surface. The obtained results showed that the beneficial role of ZrO2-BN nanosheets in improving the surface wettability, in vitro biocompatibility and corrosion protection performance of PPy coatings on Ti surface suggests a possible candidate for biomedical applications.

Effect of airborne-particle abrasion of yttria-containing zirconia dental ceramics on mechanical properties before and after regeneration firing

The zirconia-resin adhesion, crucial in fixed dental prostheses, may be mechanically enhanced by airborne-particle abrasion (APA) induced surface roughening. APA may substantially increase the strength of 3Y-TZP, which is associated with (sub)surface compressive residual stresses through t-m phase transformation. In this work, the effects of APA and regeneration firing (RF) (1000 °C, 15 min) of various zirconia dental ceramics containing 3–5 mol.% of yttria were investigated. The phase composition, (sub)surface microstructural changes, and biaxial flexural strengths coupled with Weibull statistics and fractography were analysed and compared. The results show a significant increase in strength for 3Y and 4Y specimens after APA, ascribed to the t-m transformation toughening. However, APA substantially decreased the strength of 5Y variant. After RF, the ferroelastic domain switching phenomenon was presumably the persisting mechanism to withstand the propagation of APA-induced cracks in 3Y and 4Y zirconias, not being inferior to strength values of the as-sintered counterparts.

Experimental study on simultaneous heat-water-salt migration of bare soil subjected to evaporation

Evaporation in shallow soil has a great influence on the properties of surface soil. Therefore, under evaporation conditions, research on the rule and mechanism of heat-water-salt migration in surface soil has great significance for engineering geology and environmental science. In this study, with full consideration of the initial water content, salt content, atmospheric temperature, and groundwater supply, a series of indoor evaporation tests were performed on shallow saline soil to observe the heat-water-salt migration process. In addition, before and after the evaporation test, the soil microstructure at different depths was observed and analysed to explore the influence of heat-water-salt migration on the soil. The results show that during the evaporation process, salt carried by water migrates in the soil column, and the water-vapour phase transition causes salt accumulation, which also leads to the electrical conductivity (EC) profile showing a V-shape, and the salt content in the middle of the soil column is lower than that in the end. In addition, high atmospheric temperature significantly reduces the surface water content but alleviates salt accumulation. Under the condition of groundwater supplementation, the salt accumulation in the soil column surface is rapid. By observing the microstructure, it can be seen that a flocculent structure exists in the soil before evaporation. After evaporation, the surface microstructure changes significantly, and pores and salt crystals can be observed. The results provide a reference for understanding heat-water-salt transport in arid areas.

Turning of high strength, austenitic stainless steels

High interstitial austenitic stainless CrMn steels are characterised by significantly increased work hardening ability and strength compared with conventional CrNi austenites, yet maintaining very high ductility and toughness. The machining of high interstitial CrMnCN steels is challenging in terms of process stability and economic efficiency. In this context, unfavourable chip forms, high thermomechanical loads and the superposition of different wear mechanisms in particular lead to challenges in turning operations. In the following article, different lubricant strategies are analysed for machining of CrMnN and CrMnCN austenitic stainless steels regarding chip form, mechanical tool loads and wear. Furthermore, the workpiece properties are considered with regard to surface roughness and microstructural changes.