Plastic Deformation Resistance Research Articles

Feasibility Analysis of Resource Application of Dry Flue Gas Desulfurization Ash in Asphalt Pavement Materials

To verify the feasibility of applying dry flue gas desulfurization ash (DFGDA) to asphalt pavement materials, the asphalt mastic (filler and asphalt composition) prepared by adding different proportions of DFGDA and LSP (limestone powder) into 70# matrix asphalt was studied experimentally. The asphalt mastics were subjected to the penetration test, the softening point test, and the ductility test. Moreover, the rheological properties of asphalt mastic were evaluated with dynamic shear rheometer (DSR) tests and bending beam rheometer (BBR) tests. An interaction ability index C-value based on the Palierne model was proposed to evaluate the interaction ability between DFGDA and asphalt. The influence of DFGDA asphalt on the interaction ability of matrix asphalt was observed and evaluated using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results showed that with the increasing proportion of DFGDA, the penetration of asphalt mastic gradually decreased, the softening point increased, and the ductility slightly decreased. At the same temperature, the dynamic shear modulus G* of the asphalt mortar significantly increased with increasing DFGDA content. The incorporation of DFGDA negatively affected the low-temperature plastic deformation resistance of asphalt, but the impact was weakened with the growing DFGDA amount and the powder mastic ratio. The combination mode of DFGDA and matrix asphalt depends on the physical blending, and their interaction ability mainly depends on the miscibility between DFGDA and matrix asphalt. In conclusion, DFGDA can be utilized as a novel filler in asphalt pavement materials.

Study of frictional wear and desorption of nanoparticle‐rubber blend modified UHMWPE composites

AbstractTo address the issues of abrasive wear, impact wear, and soil adhesion that can lead to wear failure and excessive operational resistance in agricultural soil touching parts during farming. This study focuses on UHMWPE composites, modified by filling Nano‐SiC as a hard phase filler and XNBR as an elastic filler. These fillers were dispersed into the UHMWPE matrix through melt blending technology to create a high‐performance composite material for the surface protective material of soil touching parts. The study discovered that by adding hard and elastic fillers to the UHMWPE matrix, the density, hardness, flexural modulus and thermal stability of the materials were all increased. Specifically, the density increased by 5.67% and the flexural modulus increased by 107%. In the block on ring wear test the volumetric wear rate decreased by 98%, while in the mortar wear test the mass wear rate decreased by 64.64%. Additionally, the contact angle on the surface of the specimen after mortar erosion and wear increased to 102.76°, 18% higher than that of pure UHMWPE. These results demonstrate that the modified fillers can improve the abrasion and plastic deformation resistance and hydrophobic desorption of UHMWPE. UHMWPE composite material, serving as the surface protection for soil touching parts, resolves the issues of abrasion of soil abrasive particles and excessive soil adhesion resistance on these parts. This significantly prolongs the service life of soil touching parts of agricultural machinery and improves the operational efficiency and economy.Highlights Research on nanoparticles and elastomer‐modified composite materials Research has shown the enhancement of UHMWPE composite materials by Nano‐SiO2 XNBR improves the plastic deformation resistance of UHMWPE composites Effects of Nano‐SiC and XNBR on the desorption behavior of composite materials UHMWPE composites reduce soil contact wear and soil adhesion

Local Instability and Deformation Control of Steel Roof of Factory Building in a Smart City

Abstract The traditional control methods of instability and deformation of steel structure neglect the analysis of its natural vibration characteristics, which lead to the poor effect of hysteretic vibration of steel structure nodes, and the stability optimization of steel structure is not ideal. Therefore, a new method to control the local instability and deformation of the steel roof is proposed. According to the steel structure composition of the upper door rigid frame and the connection mode of the frame beam and column, the roof steel structure characteristics of the workshop are analyzed. Multi-order natural frequency method is used to obtain the cumulative modal mass contribution rate of steel structure and analyze the natural vibration characteristics of steel structure. Based on the characteristics of natural vibration and element transfer matrix, the local instability control method of roof steel structure is designed. Simulation of strong vibration, using space analysis of tall-building with wall-elements (SATWE) software analysis of strong vibration under elastic load state, to obtain the external deformation of steel structure, under simulation of vibration deformation control model. Taking a chemical plant as an example, a finite element model was established to simulate the vibration wave, and the numerical simulation results of plastic deformation resistance of steel structure were analyzed. The experimental results show that the proposed method can effectively enhance the stability of steel structure and reduce its deformation degree.

Designing hydrogen-free diamond like multilayer carbon coatings for superior mechanical and tribological performance

Diamond like carbon (DLC) coatings are extensively employed for their outstanding mechanical and tribological properties. To overcome the inherent high residual stress, therefore brittleness, DLC coatings with multilayer architecture were developed in the form of stacking alternate hard and soft layers to avoid premature failure under severe loading conditions. The current study was designed to investigate the impact of bilayer thickness (hard & soft) on wear of multilayer DLC particularly at high contact stress (2.0 GPa, 2.7 GPa, 3.0 GPa, 3.4 GPa). Seven DLC multilayer (1:1 bilayer ratio) samples with 1, 2, 5, 10, 20, 40, 80 bilayers were deposited on 440C steel and the overall coating thickness was mainatined at ∼1 µm. Moreover, the bilayer thickness effect was determined on mechanical, scratch adhesion and structural properties. Transmission electron microscope (TEM) was used to visualize discrete hard and soft layers in 80 bilayers (∼6 nm thin layer). G peak suppression and ID/IG increment were observed with reduction in bilayer thickness. Hardness, modulus, elastic strain to failure (H/E), plastic deformation resistance (H3/E2) and residual stresses showed an inverse relation with bilayer thickness. Furthermore, micro scratch adhesion decreases with layer thickness reduction. Only 100 nm and above bilayer thickness samples (1, 2, 5, 10 bilayers) could survive under high contact stress while the other three (20, 40, 80 bilayers) showed brittle failure using pin-on-disc tribometer. Additionally, 10 bilayers (100 nm thickness) produced the minimum wear (∼7.9 ×10−8 mm3/Nm) at 80 N.

Microstructure and tribological properties of cold sprayed WCp/Ti composite coatings on Ti6Al4V titanium alloy

In this study, WCp/Ti composite coatings with the WC proportions of 30.1–44.1 vol% were cold sprayed using powders with WC proportions of 40–80 vol%. Coatings are well bonded to Ti6Al4V substrates, with a thickness of more than 3.8 mm, and have dense microstructure with a porosity of lower than 1.0% despite the high proportion of ceramics. The wear testing shows that coatings exhibit excellent tribological behavior with wear rates reduced by an order of magnitude compared with Ti6Al4V substrate. WC particles help develop more stable mechanically-mixed layers, obtaining a stable coefficient of friction and lower wear. The significance of crack extension resistance and plastic deformation resistance of Ti matrix reflected by H/E and H3/E2, respectively, in determining tribological behavior is also discussed.

Chemically Functionalized Graphene–Boron Nitride/Polypropylene Nanocomposites with Enhanced Nanomechanical and Anti-wear Properties

Polymers are soft materials with large molecular chains, which are softened during frictional wear, leading to bulk detachment of materials and poor wear resistance in addition to their low mechanical strength and hardness. This study developed polypropylene nanocomposites containing hydrothermal assembled graphene and boron nitride (BN@GNs) with good mechanical properties and wear resistance. To ensure good dispersion of the nanoparticles in the polypropylene (PP) matrix, they were functionalized and preparation of masterbatch using polypropylene maleic anhydride (PPMA) was adopted, while the polymer nanocomposites for this study were developed via melt compounding. The addition of the nanoparticles in the PP matrix promoted its wear resistance as all the developed nanocomposites showed a low coefficient of friction (CoF). The wear rate of the nanocomposites was dramatically reduced to a minimum of 2.05 × 10−4 mm3/Nm for the PP/3wt%BN@GNs nanocomposite from around 24.9 × 10−4 mm3/Nm for the pure PP. The nanoindentation test results of the nanocomposites also revealed improvement in their nanomechanical characteristics. For instance, PP/3wt%BN@GNs nanocomposite showed an ideal increase of about 124% nano-hardness and 65.7% nano-elastic modulus when compared to pure PP. In comparison to pure PP, all of the developed nanocomposites displayed lower nano-percentage creep and nanoindenter’s tip penetration depth, which suggest greater plastic deformation resistance.

First-principles calculations to investigate elastic, electronic, optical, and thermodynamic properties of intermetallic elements Pt3T (T = Nb, Ru, Rh, Pd, and Ag)

Different significant properties as example structural stability, stiffness constants, hardness, machinable index, band structure, interatomic bonding, optical, as well as thermal behavior of a few transitional intermetallic elements Pt3T (T = Nb, Ru, Rh, Pd, and Ag) are accompanied by ab-initio-based DFT simulation through CASTEP code. The reliability of this work has been established through the comparison of similar research-based previous work. The structural properties show a consistent relationship with the previously investigated theoretical and experimentally evident data. Investigating through the insightful elastic parameters, mechanical stabilities for all phases have been confirmed. All intermetallic phases studied in this paper show metallic nature, as confirmed by band structure and density of state calculations. In all cases, outstanding results of high bulk and plastic deformation resistance, high hardness, high melting point, and high thermal conductivity have been observed for the Pt3Ru compound. It is found (from electronic measurements) that the unique hybridization between Pt and Ru plays a key role in obtaining the better performance of Pt3Ru compound. The high bulk modulus, Young's modulus, and hardness value revealed the strong interatomic bond formation in Pt3Ru phase as well as harder type of material than others. Apart from Pt3Ru, the compounds Pt3T (T = Nb, Rh, Pd, and Ag) contain high machinability index as they have low hardness which ensured that these phases have potential applications in industry. The high melting point temperature and other excellent properties obtained for Pt3Ru compound comprise its superiority for high-temperature sector industrial applications. On the other hand, the lower minimum thermal conductivity for Pt3Pd and Pt3Ag ensured their potential applicability as TBC materials. However, all phases exhibited exceptional reflectance properties over long range photon energy, even in the UV region, which shows the applicability of these compounds to use as solar reflector materials.

The structure and micromechanical properties of TiAlSiN, TiAlSiCN coatings formed by the method of reactive magnetron sputtering

Nanostructured nitride TiAlSiN and carbonitride TiAlSiCN coatings are herein formed by reactive magnetron sputtering on various types of substrates: single-crystal silicon (100) and Titanium Grade2. To control and manage the coating process, the developed modular gas flow control complex (MGFCC) is used. The elemental composition is studied byenergy dispersive X-ray spectroscopy (EDX), the structure by X-ray diffraction (XRD), the morphology by scanning electron microscopy (SEM), whereas the micromechanical properties by nanoindentation. It is discovered that the formed coatings over the entire range of parameters α = 0.421–0.605 have a single-phase structure (Ti,Al)N, which is a disordered solid solution with a face-centered cubic (fcc) lattice. The average crystallite size of the (Ti,Al)N phase varies in the range (20–30) ± 5 nm. It is found that a decrease in the degree of reactivity α from α = 0.605 to α = 0.421 leads to an increase in the rate of deposition of nitride TiAlSiN and carbonitride TiAlSiСN coatings on silicon substrates by 200–300 %. The hardness of the formed coatings varies in the range H = 28.74–48.99 GPa, Young’s modulus E = 324.97–506.12 GPa. TiAlSiN, TiAlSiCN coatings demonstrate high values of impact strength indices H/E* = 0.07–0.12 and plastic deformation resistance indices H3/E*2 = 0.13–0.72. It is detected that the degree of reactivity α has a significant effect on the micromechanical properties of the formed coatings. The structure and micromechanical properties of the formed nanostructured nitride and carbonitride TiAlSiN, TiAlSiCN coatings are suitable for use in space technology applications.

The Role of Period Modulation on the Structure, Composition and Mechanical Properties of Nanocomposite Multilayer TiAlSiN/AlSiN Coatings

This paper presents the results of the investigation of a multilayer TiAlSiN/AlSiN coating. A novel coating architecture with a period consisting of nanocomposite sublayers of TiAlSiN and AlSiN was developed. We discovered that the combination of a harder sublayer with a more elastic one allows for obtaining a suitable combination of superhardness and enhanced toughness. The coating was deposited by cathodic arc technology. The EDS, XRD, and XRS analyses revealed that the nanocomposite structure is composed of TiAlSiN and AlSiN nanocrystallites, with sizes of 12–13 nm and 4–5 nm, respectively. The nanograin phase is incorporated in an amorphous Si3N4 matrix. The achieved structure causes the presence of four factors contributing to the hardness increase: nanocomposition, solid solution, refinement hardening, and the formation of many interfaces. An instrumented indentation test was used to investigate the mechanical properties. The developed coating possesses a superhardness of 49.5 GPa and a low elastic modulus of 430 GPa, resulting in an improved elastic strain resistance of 0.11, a plastic deformation resistance of 0.58 GPa, and an elastic recovery of 68%. These results imply that the developed coating combines high stability with mechanical degradation under external influence and provides an improved ability to absorb energy at deformation before fracture, and high elastic recovery. The investigation of the effect of the period modulation on the structure, composition, and mechanical properties of the nanocomposite multilayer TiAlSiN/AlSiN coating showed that the superhardness was due to the nanocomposite and solid solution hardening rather than the increased number of interfaces. The demonstrated combination of superhardness with high elasticity and improved toughness determines the developed nanocomposite TiAlSiN/AlSiN coating as very suitable for industrial applications such as high speed and dry machining.

A multi-method coupled approach to simulate crack growth path and stress-strain field at the tip of the growing crack in the dissimilar metal welded joint

This study investigates the crack growth path and the stress-strain field at the tip of the growing crack within various locations of a dissimilar metal welded joint (DMWJ), incorporating an in-depth analysis of the joint's heterogeneous material properties and microstructure. Several novel finite element simulation methods are employed. Among these, a “user-defined field" is developed to achieve a continuous transition of material mechanical properties within local regions of the joint. Subsequently, the crack growth path within different parts of the joint is analyzed using the extended finite element method (XFEM). Upon determining the crack growth path, the De-bond method, through a sub-model focusing on the local regions of the crack tip, is utilized to analyze the stress-strain field at the tip of the growing crack under constant load conditions. The findings reveal that the mechanical heterogeneity at the local region of the welded joint impacts the crack growth path. Stress corrosion cracking (SCC) tends to favor the side with higher yield strength. Materials with higher yield strength typically exhibit lower plastic deformation and crack resistance, resulting in a greater driving force for crack propagation and making SCC more prone to propagation. Significant residual stress and strain can be observed along the path after growth. The primary aim of this study is to establish a coupled multi-method approach, integrating XFEM and the De-bond method, to accurately predict the crack growth path and analyze the stress-strain field at the tip of the growing crack. This information could be instrumental in assessing the integrity of DMWJs.

TiNbN Hard Coating Deposited at Varied Substrate Temperature by Cathodic Arc: Tribological Performance under Simulated Cutting Conditions.

This study focused on investigating the adhesion and tribological properties of niobium-doped titanium nitride (TiNbN) coatings deposited on D2 steel substrates at various substrate temperatures (Ts) under simulated cutting conditions. X-ray diffraction confirmed the presence of coatings with an FCC crystalline structure, where Nb substitutes Ti atoms in the TiN lattice. With increasing Ts, the lattice parameter decreased, and the crystallite material transitioned from flat-like to spherical shapes. Nanoindentation tests revealed an increase in hardness (H) with Ts, while a decrease in the elastic modulus (E) resulted in an improved elastic strain limit for failure (H/E) and plastic deformation resistance (H3/E2), thereby enhancing stiffness and contact elasticity. Adhesion analysis showed critical loads of ~50 N at Ts of 200 and 400 °C, and ~38 N at Ts of 600 °C. Cohesive failures were associated with lateral cracking, while adhesive failures were attributed to chipping spallation. The tribological behavior was evaluated using a pin-on-disk test, which indicated an increase in friction coefficients with Ts, although they remained lower than those of the substrate. Friction and wear were influenced by the surface morphology, facilitating the formation of abrasive particles. However, the absence of coating detachment in the wear tracks suggested that the films were capable of withstanding the load and wear.

Performance evaluation of crumb rubber and bio-based polyurethane compound in terms of rheological and aging properties of asphalt binder

This study explored the effects of the combined use of CR and polyurethane (PU), whose use in bitumen modification is still in its infancy. The polymeric 4.40-diphenylmethane diisocyanate (MDI) and palm-oil-based polyol were used for the PU modification. A 4:1 M ratio of NCO/OH was found to be successful in forming urea bonds in the CR-modified binder. The performance of CR and CR + PU-modified bitumen was compared with the most widely used SBS modification. The binders were subjected to conventional and rheological tests. Fourier transform infrared spectroscopy was utilized to evaluate the effect of aging. The use of 8 %CR and 4% PU together provided a considerable performance improvement over the use of CR alone and that this combined binder provided better plastic deformation resistance, and low-temperature behavior than the 4 %SBS modification. The chemical reaction between PU and CR prevented the decomposition and had a significant effect on increasing the storage stability. The use of PU with CR was found to reduce chain scission, condensation and oxidation caused by aging.

Influence of Physical and Mechanical Parameters on Cavitation Erosion and Antifouling Behaviour of Multilayer Silica-Based Hybrid Sol–Gel Coatings on Aluminium Alloys

Sol–gel coatings can provide anti-fouling and erosion resistance while being safe to use in the marine environment. MAPTMS/ZPO multilayer coatings deposited on the AA2024-T3 aluminium surface using the dip-coating method at three different thicknesses (2, 4, and 6 µm) are investigated in this work. The coatings are characterised in terms of physical and mechanical properties, and these properties are investigated in comparison to previously obtained cavitation erosion resistance levels of the coatings. Additionally, the efficiency of the coatings against biofouling was assessed using Phaeodactylum tricornutum, a marine diatom. The influence of the formation of organic–inorganic hybrid materials (OIHMs) from the prepared sols on the physical and mechanical properties of the coatings were analysed. A variety of techniques, including attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), water contact angle (WCA) measurements, pencil hardness testing, cross-cut adhesion testing, a roughness profilometer, and nano-indentation, were performed on the bare and coated substrates. The results indicated that the thickness, hydrophobicity, and adherence of the coatings are strongly affected by the roughness. The elastic strain failure (H/E) and resistance to plastic deformation (H3/E2) coefficients were higher than those of the bare substrate before and after the cavitation erosion test, indicating that the coating had a higher ability to withstand deformation in comparison to the substrate alone. Furthermore, the microscopic analysis of a marine diatom, Phaeodactylum tricornutum, revealed that coated surfaces exhibited a decreased rate of bacterial adhesion and biofilm formation. The data show that sol–gel formed coatings outperform uncoated AA2024-T3 in terms of hardness, elastic strain, plastic deformation, and biofouling resistance. These characteristics are attributed to the coatings’ mechanical and adhesive capabilities, as well as their tribological behaviour.

Tribological Behavior of Doped DLC Coatings in the Presence of Ionic Liquid Additive under Different Lubrication Regimes

Diamond-like carbon (DLC) coatings are widely used in industries that require high durability and wear resistance, and low friction. The unique characteristics of DLC coatings allow for the possibility of creating adsorption sites for lubricant additives through the doping process. In this study, the combined use of europium-doped diamond-like carbon (Eu-DLC), gadolinium-doped diamond-like carbon (Gd-DLC), and pure DLC coatings and an ionic liquid (IL) additive, namely, trihexyltetradecylphosphonium bis (2-ethylhexyl) phosphate [P66614] [DEHP], with a 1 wt.% concentration in polyalphaolefin (PAO) 8 as a base lubricant was investigated. Higher hardness, higher thin-film adhesion, a higher ratio of hardness to elastic modulus, and a higher plastic deformation resistance factor were achieved with the Gd-DLC coating. The CoF of the Gd-DLC coating paired with the IL was superior compared to the other pairs in all lubrication regimes, and the pure DLC coating had a better performance than the Eu-DLC coating. The wear could not be quantified due to the low wear on the surface of the DLC coatings. The friction reduction demonstrates that tribological systems combining Gd-DLC thin films with an IL can be a potential candidate for future research and development efforts to reduce friction and increase the efficiency of moving parts in internal combustion engines, for instance.

Structural-phase states and micromechanical properties of nanostructured TiAlCuN coatings

TiAlCuN coatings were deposited by reactive magnetron sputtering on substrates of single-crystal silicon, and Titanium Grade2 wafers. To control and manage the coating deposition process by reactive magnetron sputtering, a previously developed modular gas flow control complex (MGFCC) was used. The elemental composition was studied by energy-dispersive X-ray spectroscopy (EDX). The structural-phase state of coatings was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties, such as hardness and Young’s modulus, were investigated by the nanoindentation using a CSM Instruments Nanohardness Tester NHT2 (Switzerland). The influence of deposition parameters such as: Ti and Al content, reactivity degree α, and nitride concentration on structure and mechanical properties was considered. It was found that a decrease in the reactivity degree α from 0.605 to 0.474 leads to a 23 % increase in the deposition rate of TiAlCuN coating. It was detected that adding Cu to the coating content decreases the mean sizes of crystallites and growth columns in comparison with the TiAlN analogues due to its segregation along crystalline boundaries and thus advances better mechanical characteristics. The hardness of TiAlCuN coatings varies in the range of H = 29.3–35.4 GPa, Young’s modulus E = 235.9–267.6 GPa. The impact strength index as the H / E∗ ratio and the plastic deformation resistance index H3 / E∗2 were calculated. The formed nitride coatings are suitable for use in space technologies.

Structural and mechanical properties of magnetron-sputtering-deposited Ta- and Al- based coatings – a comparative analysis

A comprehensive evaluation of the structure and the nano-mechanical characteristics of single and two-layer nano-structured coatings AlN/Al2O3, TaN/Ta2O5 grown on the surface of metallic materials. The formation of a two-layer structure improves the mechanical and tribological properties of the coating-substrate system, such as the plastic deformation resistance and anti-wear performance. The results indicate that the proposed two-layer nanostructured nitride-oxide coatings based on aluminum and tantalum are promising candidates for biomedical applications.

Comparison of Mechanical and Tribological Properties of TiN and ZrN Coatings Deposited by Arc-PVD

The continuous development of thin coatings for different applications and using various coating meth-ods require the characterization of these newly formed surfaces to evaluate their utility properties. Binary thin coatings of titanium (TiN) and zirconium (ZrN) nitrides were prepared using the Arc-PVD (Ca-thodic Arc Deposition) method. Differences were observed in the structure and morphology of the thin coatings and the change in tribological properties at room and elevated temperatures (150 °C and 300 °C). The research is focused on evaluating the frictional properties of the coating using the Ball-on-Disc method in the dry friction mode. The emphasis is placed on the resistance of the thin coating to wear. The nanohardness was measured to be 26.2 GPa for TiN and 24.8 GPa for ZrN. Index of resistivity against plastic deformation H³/E² (plastic deformation resistance) for ZrN coating – 0.087 and TiN coating – 0.095, H/E (plasticity index) for ZrN – 0.059 and TiN – 0.060. Better friction properties and wear resistance (at 150 °C) were found for the TiN coating compared to the ZrN coating.

First-principles investigation of the effect of Cr/(Ti+Cr) ratio on the structure and mechanical properties of Al-rich Al0.6875Ti0.3125-xCrxN coatings

Aluminum-rich Al0.6875Ti0.3125-xCrxN coatings with different Cr/(Ti + Cr) ratios (0%, 20%, 40%, 60%, 80%, 100% respectively) are investigated using first principles methods based on density functional theory. The results show that the structural stability of the Al0.6875Ti0.3125-xCrxN coating decreases with the increase of Cr/(Ti + Cr) ratio. Al0.6875Ti0.125Cr0.1875N (Cr/(Ti + Cr) = 80%) and Al0.6875Ti0.0625Cr0.25N (Cr/(Ti + Cr) = 100%), with maximum bulk modulus, have the highest hardness (44 GPa). In addition, the analysis of band structure, density of states and charge density difference reveals that, with the increase of Cr/(Ti + Cr) ratio, the Al–N covalent bond strength is weakened while the metallic bond strength of the coating is enhanced, indicating that toughness of the Al0.6875Ti0.3125-xCrxN coating is enhanced. With respect to the Al0.6875Ti0.125Cr0.1875N (Cr/(Ti + Cr) = 60%) coating, the effect of metallic bond strength is the most evident. Thus Al0.6875Ti0.125Cr0.1875N coating, with the largest H3/E2 value (0.54), owns the best toughness and plastic deformation resistance.

Microstructure change characteristic and fracture mechanism of Ti-47.5Al-2.5V-1.0Cr-0.2Zr alloy during high temperature tensile deformation

Changes in the microstructure characteristics and fracture mechanism of Ti-47.5Al-2.5 V-1.0Cr-0.2Zr alloy during tensile deformation were studied by high temperature tensile tests at 750–900 °C and strain rate of 10−5–10−3 s−1. The experimental results indicate that when the tensile temperature increases or the strain rate decreases, the number of small dimples in the tensile fracture structure increases, the proportion of cross-layer fracture decreases, the dimples have torn edges, and the plastic deformation resistance increases. The higher tensile temperature corresponds to a higher dynamic recrystallization (DRX) ratio, and the number of dislocations near the DRX structure is reduced, which shows that the rheological softening effect is significantly enhanced. A lower strain rate corresponds to a higher proportion of DRX and a smaller proportion of lamellar microstructure. Dislocation slip is the main deformation mode; stacking faults can be observed in DRX grains. The changes in the hot deformation microstructure directly reflect decrease of high temperature tensile strength in macroscopic flow behavior. Under the action of tensile stress, holes usually form at the lamellar grain boundary, and the aggregation of multiple micro-holes will merge and connect to form micro-cracks. Cracks are generated and propagated between layers, and the tendency of holes or cracks generated at lower deformation temperatures or higher strain rates is greater. When the stress concentration reaches a certain critical value, the specimen will eventually fracture.

Effect of Power on Structural and Mechanical Properties of DC Magnetron Sputtered Cr Coatings

Cr coatings were deposited on the surface of PCrNi1MoA steel by DC magnetron sputtering. The effects of power (100~250 W) on the structure and mechanical properties of the coating were systematically studied. The results show that all Cr coatings have strong (110) preferred orientation and anisotropic surface morphology, and the cross sections are columnar structures. With the increase in power, the deposition rate increases linearly, the surface roughness and grain size increase gradually, and the nanomechanical properties decrease first and then increase slightly. At 100 W, the columnar grain of the coating is compact and continuous, and the wear resistance and plastic deformation resistance are the best, with the highest binding force of 27.04 N. At 200 W, due to grain growth and tensile stress, internal defects increase, and mechanical properties are poor. The combination of coating and substrates is not tight enough, and it is easy to fall off and fail under the action of external force. When the power reaches 250 W, the higher bombardment rate helps the coating release stress, and reduce porosity.