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Preheating is the first step for thermal-mechanical processing of the materials. Several preheating schedules were designed based on industrial manufacturing to explore their effect on the microstructure and mechanical properties of AA2099 Al-Li alloy during the following hot rolling. The results show that the mechanical properties of as-rolled sheets are quite sensitive to preheating. Various types of secondary phases, including δ’, T1 and T2 phases, were precipitated during the heating process. The difference among precipitates is the main reason to induce the variation of mechanical properties for as-rolled sheets. A rapid heating rate gave rise to the precipitation of δ’ phase, which largely promoted yield stress and ultimate tensile strength in as-rolled sheets. T1 phase was more favorable in the preheating with a holding period at 150–250 °C, which caused a moderated strain hardening behavior. Precipitates formed during preheating induced different slip behaviors in the following deformation. The coexistence of T1 and δ’ phase could restrict planar slip, which inhibited the formation of the shear band. The difference in the activity of non-octahedral slips and planar slips determined the strain hardening effect, which should be the reason for the variation of mechanical properties of as-rolled sheets.

Microstructure characteristics and mechanical behavior of AA2099 Al–Li alloy with no pre-existing Li-containing precipitates (AA2099-1 sample), pre-existing δ′ precipitates (AA2099-2 sample), pre-existing T1 phase (AA2099-3 sample) and pre-existing T2 phase (AA2099-4 sample) are systematically investigated via isothermal uniaxial compression at 250 °C in the present study. Experimental results demonstrate that at the onset of plastic deformation, dynamic precipitation of small-sized T1 phase occurs rapidly within AA2099-1 sample, while it will be hindered within AA2099-2 sample. The increasing plastic strain benefits to dynamic precipitation of small-sized T1 phase in AA2099-2 sample. Consequently, AA2099-1 and AA2099-2 samples possess similar and intermediate mechanical behaviors. In terms of AA2099-3 sample, the existence of large-sized T1 phase results in the maximum yielding stress. However, some regions within these large-sized T1 precipitates are suspected to be sheared by cross-slip, leading to the destruction of crystallographic structure and the formation of Al matrix intervals. This aspect is responsible for the gradual degradation in true stress-strain curve after peak stress. As for AA2099-4 sample, dynamic precipitation rarely happens during plastic deformation and the interaction between dislocation and the pre-existing T2 phase belongs to Orowan looping, resulting in the minimal mechanical response. Besides, AA2099-1 sample possesses the average minimum deviation angle (MDA) of ~ 16.5° between the loading direction and the crystal direction, whereas AA2099-4 sample owns the average MDA of ~ 7.5°. The difference in MDA is mainly attributed to δ′ phase and T1 phase, which will separately accelerate and postpone the rotation of orientation towards the crystal direction.

In this study, typical microstructural characteristics of a metastable β Ti alloy (Ti–5Al–5Mo–5V–3Cr–1Fe) forged in a dual-phase region (strain of 54% at 820 °C) were investigated in detail by the combined use of X-ray diffraction, energy dispersive spectroscopy, electron channeling contrast imaging and electron backscatter diffraction techniques. Results show that the microstructure of the forged alloy is composed of bulk α grains, α plates and β matrix. The bulk α grains correspond to retained primary α phase (αp, average grain size ~ 2.4 μm), while the α plates are secondary α phase (αs, width ~ 70 nm) precipitated from the β matrix during air cooling. During forging, the β matrix experiences dynamic recovery with many subgrains and significant orientation gradients formed. Analyses of the orientation relationship between the α and β phases show that the Burgers orientation relationship is not maintained between some αp and β phases, which should be related to thermal deformation-induced changes of their orientations. In contrast, all of the αs plates are found to maintain well the Burgers orientation relationship with the β phase.

The true stress–strain curves of an as-extruded state AA2099 were determined by uniaxial compression tests under various hot deformation regimes. Constitutive analysis of the curves allowed calculation of the hot deformation activation energy (QHW). The microstructure of the as-compressed specimens were also characterized by electron back scatter diffraction (EBSD). EBSD data analyses showed that the major restoration mechanism corresponding to common industrial extrusion regimes was dynamic recovery. The precipitates in three states (T83, as-homogenized, and as-extruded) were characterized by X-ray diffraction (XRD) phase analyses and transmission electron microscopy. The results revealed that the QHW was closely relevant to the precipitates strengthening. The finite element method simulation results and the microstructure of the extruded products confirmed that AA2099 in as-extruded state possessed good workability.

A sandwich structure of Mg alloy bulk consisted of two types of texture was fabricated by pre-twinning deformation. Its mechanical response and work hardening behavior during uniaxial compression were deeply analyzed to investigate the competition mechanism between basal slip and detwinning. Results showed that pre-twinning layer was a soft region. It undertook more than half of the strain by one third of the volume fraction of the bulk at the beginning of deformation. Slip behavior was significantly enhanced by detwinning and it took a more important role to coordinate local strain. Texture bonding promoted slip behavior in the grains exhibited “hard” orientations. Activation of detwinning behavior in pre-twinning region was mainly depended on basal slip behavior of their parents.

The microstructure and texture characteristics of commercial pure Ti after friction stir processing (FSP) with a slow rotation speed were studied. The shoulder friction zone (SFZ) which did not exist in the FSPed pure Ti with normal rotation speed (> 250 rpm) was observed in the sample treated with a slow rotation speed of 180 rpm. The texture of SFZ in the pure Ti was affected by shear stress from the shoulder of stir tool and the c-axes of the grains in this zone were nearly parallel to the processing direction. While crystallographic texture in the normal stir zone (SZ) were nearly perpendicular to the processing direction. The maximum depth of SFZ in the sample with 180 rpm was 1.2 mm, which decreased with the increased rotation speed until it disappeared. The grains in the SZ of specimen following FSP at a slow rotation speed were fine and homogeneous. The microhardness increased from 150.2 HV to 191.6 HV after FSP at 180 rpm. The microhardness trends were related to grain sizes, work hardening and texture evolution. The slow rotation speed processed alloy boosted the yield strength by 71.7% after the FSP.

A typical metastable β Ti alloy (Ti–5Al–5Mo–5V–3Cr–1Fe alloy) was β-solution treated (890 °C for 10 min) and then cooled at different rates (in water (WC), air (AC) and furnace (FC)). To clarify specific effects of β-cooling rates, multiple characterization techniques were jointly utilized to reveal their microstructural and orientation characteristics in detail, with hardnesses also measured and correlated with specific microstructures. Results show that both the WC and the AC specimens are mainly comprised of recrystallized β grains with no α phase, while the FC specimen consists of coarse equiaxed β grains, intragranular acicular α phase (width ∼48 nm) and grain boundary α phase. The Burgers orientation relationship is strictly obeyed during β→α transformation in the FC specimen. When adjacent β grains share a common 110 > axis, the boundary α phase maintains such orientation relationship with both of them. Compared to the as-received specimen (428 ± 9 HV), the WC (309 ± 5 HV) and the AC specimens (297±3HV) are softened, which can be attributed to the coarsened β grains as well as the disappearance of α phase and deformed structures. For the FC specimen, dense fine α precipitates appear inside β grains during slow cooling, leading to increased hardness (444 ± 9 HV).

A medium-strained (13% cold-drawing) 316L austenitic stainless steel rod was subjected to annealing between 750 and 1100 °C. Electron backscatter diffraction and electron channeling contrast imaging techniques were jointly employed to investigate the development of microstructures and grain boundary character distribution during the annealing treatments. Results show that annealing at temperatures below 900 °C does not evidently change microstructures of the as-drawn specimen. Full recrystallization is observed after the temperature reaches 1000 °C and the deformation microstructures are replaced by fine and uniform recrystallized grains. A large number of annealing twins (with Σ3 misorientation) are produced by the recrystallization, leading to markedly increased fractions of special boundaries (fSB). The maximum fSB is found to be 67.3% in the present study. In addition, for the recrystallized grains, rapid growth is noticed at relatively high temperatures due to easy migration of grain boundaries.

An annealed Inconel 718 alloy was surface-treated by pulsed laser at three different powers (100, 50 and 25 W). Microstructural changes induced by the laser treatments were characterized by use of electron backscatter diffraction and electron channeling contrast imaging techniques. Results show that both annealing twins and strengthening precipitates profusely existing in the as-received specimen are dissolved at elevated temperatures during the laser irradiation. Meanwhile, in the melting zone (MZ), densities of low angle boundaries (LABs) are greatly increased with a large number of Laves phases preferentially distributed along such LABs. For different specimens, widths and depths of their MZs are found to be gradually reduced with decreasing the laser powers. Orientation analyses reveal that the columnar grains in the MZ of the 100 W specimen could inherit orientations existing in the matrix while lower laser powers promote the formation of more nuclei with scattered orientations to grow to be granular grains in the MZ. Hardness tests reveal that the MZs of all laser-treated specimens are softer than the matrix probably due to both precipitate dissolution and grain coarsening.

Amorphous Si–C-based (a-SiC) thin films as protective coating have been attracting more and more attentions. But there are contradictory reports in the literature about the effect of sputtering power on the structural and mechanical properties of a-SiC films. Here, the influence of sputtering power on structural and mechanical properties of a-SiC thin films deposited by pulsed magnetron sputtering have been investigated. The results show that as-prepared films have a columnar structure and cauliflower-like pattern at lower sputtering power (100 W). Increasing the sputtering power from 100 W to 180 W, the columnar feature disappears and the thin films become denser. Meanwhile, the density of Si–C bond increases and the sp3/sp2 radio decreases. The hardness (H) and elastic modulus (E) of the a-SiC thin films increase when the sputtering power increases from 100 to 120 W and then their almost keep constant when the sputtering power increases from 120 to 140 W. Further increases in sputtering power, the H and E increase again. The maximum H and E are about 20.2 GPa and 223.1 GPa at 180 W, respectively. Reason for excellent mechanical property is proposed in combination with the theory analysis and experiment results.

The formation possibility of high-entropy alloy (CrNbSiTiZr)C was first studied by analyzing thermodynamics parameters through first-principles calculation. Then, the (CrNbSiTiZr)C film was successfully deposited by reactive radio frequency magnetron sputtering. Theoretical analysis results show that the mixing enthalpy and entropy values of (CrNbSiTiZr)C were 18.45 kJ/mol and 0.805 R, respectively, indicating that (CrNbSiTiZr)C is thermodynamically stable above the temperature of 2758 K. Experimental results show that the concentration of each metal element in the film is near an equimolar ratio and a mixture of Cr3C2, NbC, SiC, TiC, ZrC, and oxide formed in the (CrNbSiTiZr)C film. Moreover, the as-prepared film possesses a single B1 structure with a (111) preferred orientation and exhibits high nanohardness, elastic modulus, and fracture toughness. The friction coefficients and wear rate of the (CrNbSiTiZr)C film is as low as 0.3 and 4.2 × 10−6 mm3/N·m, respectively. The film also shows a superior corrosion resistance in a 3.5 wt% NaCl solution, a positive Ecorr and a low icorr value of −189 mV and 0.0026 μA/cm2, respectively. The film is proposed for industrial applications given its excellent mechanical, tribology, and corrosion performance and based on the theoretical analysis and experiment results.

To improve the wear resistance of medical titanium alloy, Ta coatings were prepared by magnetron sputtering method on Ti6Al4V substrates. Phase structure and surface morphology of Ta coatings were characterized by X-ray diffraction and atomic force microscope, respectively. The properties of Ta coatings, including adhesion, nano-hardness, and wear resistance, were tested using nano-scratch, nano-indentation and tribometer, respectively. The results show that both stable body-centered cubic (α-Ta) phase and metastable tetragonal phase (β-Ta) coexist in a multi-layer structure, and it shows a non-columnar feature. Interestingly, only a pure phase with columnar crystals is found in monolayer Ta coating. A body-centered cubic (α-Ta) phase is found in a monolayer prepared under the pulse power bias voltage with low deposition temperature. A pure metastable tetragonal phase (β-Ta) is prepared under the direct current bias voltage, which has the best adhesion and wear resistance compared with other Ta coatings.

Hot compression deformation tests of AZ80 and AZ80-2 wt.% Sn magnesium alloys were performed on Gleeble-1500 at deformation temperature of 350 °C and strain rate of 0.1 s−1 to analyze the effect of Sn on the microstructure evolution. The results indicated that the addition of Sn promoted dynamic recrystallization and decreased flow stress during hot compression. Dynamic dissolution of discontinuous precipitation Mg17Al12 phases was promoted and dynamic precipitation of Mg17Al12 phases was suppressed in AZ80-2 wt.% Sn alloy. The quantity of Mg17Al12 phases of thermally compressed AZ80-2 wt.% Sn alloy was less than that of AZ80 alloy. Texture intensity increased in AZ80-2 wt.% Sn alloy during hot compression due to Mg17Al12 phases effectively induced particle-stimulated nucleation in recrystallization.

The tribocorrosion behaviour of biomaterial Ti-25Nb-3Mo-3Zr-2Sn alloy in Ringer's solution was evaluated by micro-abrasion experiments, electrochemical tests and scanning electron microscope (SEM) observations. Potentiodynamic polarization results suggested that the effect of particle concentration on the electrochemistry characteristic is greater than the applied load. When the particle concentration and applied load were 0.05g·cm-3 and 0.25N, respectively, the Ecorr reached the maximum as -0.381V. The micro-abrasion-corrosion results showed that the wear rates of the Ti-25Nb-3Mo-3Zr-2Sn alloy increased with increasing particle concentration and decreased as applied load increased. The wear rates acquired under various conditions regarding to the main wear mechanism of two-body grooving wear with less three-body rolling wear; three-body abrasive wear modes are more efficient at material loss than two-body wear. The variation in material loss indicated that the contribution of corrosion is lower than the contribution of micro-abrasion. The wear regime, wastage and micro-abrasion-corrosion synergy maps associated with the particle concentration and applied load were established to evaluate the tribocorrosion behaviour of the Ti-25Nb-3Mo-3Zr-2Sn alloy as a potential surgical implant material.

Fluorine doped diamond-like carbon (F-DLC) coatings were deposited on Ti-6Al-4V alloy using a hollow cathode plasma immersion ion implantation deposition system. The aim of this work is to investigate the influence of F content on the surface morphology, structure, mechanical and tribological properties (under air and stroke-physiological saline solution) of the F-DLC coatings. The results reveal that the ratio of H/fE instead of H/E can be well predicting the anti-wear results when the F-DLC coatings have enough adhesion strength, where H is hardness, E is Young's modulus and f is friction coefficient. The F-DLC coatings with high F content exhibit excellent tribological property under air. The low F content F-DLC coatings present super-low friction coefficient and wear rate in stroke-physiological saline solution. Reasons for the tribological property are proposed in combination with the films' morphology and mechanical property.

Cylindrical specimens of as-extruded AA2099 Al-Li alloy are uniaxially compressed at temperatures ranging from 360 °C to 520 °C and strain rates ranging from 0.001 s−1 to 10 s−1. Processing map of these specimens was established. Electron backscatter diffraction (EBSD) measurements were performed for specimens deformed under various conditions to probe their microstructures and restoration mechanisms. Stored energies in various specimens are calculated based on statistics of low angle boundaries via EBSD data. The remarkable decrement of stored energy and misorientation characteristics reveal that dynamic recrystallization (DRX) happens at 480–520 °C and 0.001–0.1 s−1. Obvious DRX nucleation further suggests that this process should be classified to discontinuous dynamic recrystallization (DDRX). Stored energies in various specimens strongly affect the extents of dynamic recovery and dynamic recrystallization. By systemically considering the processing map and restoration behaviours of the specimens, the dynamic recrystallization regimes and the central high- η regimes are determined to correspond to preferable thermo-mechanical processing parameters for the as-extruded AA2099 Al-Li alloy.

The tribocorrosion behavior of the Ti-30Zr alloy as dental implant in Hank’s solution was evaluated. The results demonstrated that the wear volumes of the alloy increased as the applied load increase with/without electrochemical corrosion. The wear volumes acquired with corrosion exceeded the wear volumes without corrosion, whereas the difference between these two increased as the load increased. The material loss induced by the corrosion increased and the corrosion potential decreased as the loads increased, due to the interaction between wear and corrosion. The potentiodynamic polarization curves were acquired during wear. The corrosion potential (Ecorr) of −0.493 V was acquired at 1.0 N, while the Ecorr of −0.786 V was acquired at 5.0 N, indicating that the potential moved negatively as the applied loads increased, due to mechanical wear. Through observations of the 3-dimension surface and the SEM images of the worn surfaces, the visible scratches/grooves were observed along the sliding direction, indicating a predominant abrasive mechanism.

Solid solution treated AA 2099 alloy was rolled by a total reduction of 80% at both room and cryogenic temperature. Results show that nanocrystalline grain structure with a size around 20–100 nm was only observed in the cryogenic temperature rolled sample at high rolling strain. The formation of those nanograins related to shear banding behavior. Shear banding behavior was greatly promoted by cryogenic temperature rolling, which had a strong influence on mechanical homogeneity of rolled samples. The width of these high-density shear bands is around 0.2–8 µm. Shear strain partitioning between slip and shear banding was depended on slip behavior in deformed grains. Strain concentration inside shear bands may give rise to an obvious temperature increase, which caused significant grain refinement in or near the shear bands. The growth of nano-grains is retarded due to limited heat and pinning effect of nanosized precipitation.

High-entropy alloy (HEA) coatings exhibit high hardness and high strength and have attracted wide attention. The improvement in the tribological performance, such as low friction coefficient and wear rate, is a longstanding challenge and is critical in the broad application of HEA coatings. In this study, a series of CrNbTiMoZr coatings was synthesized using the direct current magnetron sputtering by tuning substrate bias voltages. A continuous transformation in the structure from the amorphous phase to the face-centered cubic phase was observed in HEA carbide coatings. The residual stress and the hardness monotonously increased with the substrate bias voltage. The addition of carbon reduced the friction coefficient and the wear rate of HEA coatings. Consequently, we achieved a HEA carbide coating at −200 V combined with high hardness (17.4 GPa), low friction coefficient (0.3–0.4), and low wear rate (1.18 × 10−6 mm3·N−1·m−1). This study provides a new guidance for designing new HEA coatings with high strength and low wear.

CrNbSiTiZr high-entropy alloy films with different substrate bias voltages (from 0 V to–200 V) were fabricated on 304 stainless steel and Si substrates by radio-frequency magnetron sputtering. The microstructure, mechanical properties, tribological performance, and corrosion resistance were investigated in detail. Results show that all the as-fabricated films exhibit an amorphous phase. The columnar structure becomes featureless with the increase substrate bias due to re-sputtering effects and densification of the film. The film deposited at the bias of –50 V has a high residual compressive stress of –0.82 ± 0.04 GPa and a high hardness of 12.4 ± 0.3 GPa. The wear mechanism of the film is adhesive and slightly abrasive at low negative bias (0, –50, and –100 V), and that at high negative bias (–150 and –200 V) is abrasive. Polarization and electrochemical impedance spectrum measurements reveal that all films have a superior electrochemical corrosion resistance to the 304 stainless steel in 3.5 wt% NaCl solution, which indicates that the film can effectively protect substrate from corrosion. The values of Ecorr, icorr, and Rpo of the film deposited at the bias of –50 V are −283 mV, 0.0178 μA/cm2, and 2.084 × 106 Ω‧cm2, respectively.

Friction stir processing (FSP) was successfully performed on ultra-light dual-phase LZ91 Mg Li alloy, which provided a chance to study the microstructure and texture evolution of this alloy during severe plastic deformation. The results showed that LZ91 Mg Li alloy could be processed successfully with 200–400 rpm, 25 mm/min, and water cooling during FSP. No defects were observed on the surface and in the cross-section. The microstructure was strongly influenced by the material flow modes during FSP. Two greatly phase refinement regions were found in the stir zone where the α-Mg and β-Li phases were refined to submicron scale and homogeneously mixed. Maelstrom currents flow between two threads on the pin triggered this phase fragment. The high rotation rate of FSP leads to a remarkable recrystallization and grain growth due to the high heat input. The severe plastic deformation caused a phase transformation inside the refined α-Mg phase. The new phases enriched Li element exhibited a coherent relationship with the matrix. It shows that FSP promoted the short-term diffusion in refined α-Mg.

In order to manifest the influence of specific microstructural component on the development of severe localized corrosion in an AA2099 aluminum–lithium alloy, the corrosion behavior of the alloy subjected to solution heat treatment, cold working and artificial ageing was investigated. Immersion testing and potentiodynamic polarization were employed to introduce localized corrosion; scanning electron microscopy and transmission electron microscopy were used to characterize the alloy microstructure and corrosion morphology. It was found that the susceptibility of the alloy to severe localized corrosion was sensitive to thermomechanical treatments. Additionally, the state of alloying elements influenced the mechanism of localized corrosion propagation. Specifically, the alloy in T8 conditions showed higher susceptibility to severe localized corrosion than that in other conditions. During potentiodynamic polarization, the alloy in solution heat-treated and T3 conditions displayed crystallographic corrosion morphology while the alloy in T6 and T8 conditions exhibited selective attack of grain interiors and grain boundaries in local regions.

The deposition parameters of high-entropy alloy films significantly influence their performance due to effective control of their microstructure. Thus, these parameters have become a research hotspot. In this study, CrNbTiMoZr high-entropy alloy films of amorphous or nanocrystalline solid solution were synthesized by direct current magnetron sputtering on silicon wafers and 304 stainless steel under different substrate bias voltages. The films' microstructure and tribo-mechanical properties were studied in detail. Results showed that the microstructure of films transformed from columnar structure to featureless with increased substrate bias voltage. In the nanoindentation test, the film deposited at −150 V exhibited the highest hardness of 9.7 GPa. Nevertheless, the CrNbTiMoZr films displayed excellent tribological properties under low bias voltage. Overall, our findings can guide the design of other novel high-entropy alloy films.

Peeling is considered to be the main technical obstacle for coating applications. There are many factors that affect the peeling process of coatings. The interfacial properties of the coating and substrate play a crucial role in the peeling process. In this study, the work of adhesion (Wad), interface energy (γi), and electronic structure of diamond (001)–Si(001) and Si(001)–Ti (0001) interface models have been investigated using first-principles calculations. The results indicate that the diamond (001)–Si(001) interface exhibits larger Wad and smaller γi values when compared with the Si(001)–Ti (0001) interface. However, the Wad of diamond–diamond, Si–Si, and Ti–Ti is 15.92, 4.92, and 3.84 J/m2, respectively. When compared with the two interface models, the Wad of Ti–Ti is the smallest, indicating that it will be the first to undergo deformation during the shear process. In addition, analysis of the charge density difference and density of states revealed that the interfacial Ti–Si bond is a covalent–metallic bond, which is much weaker than the Si–C bond (covalent bond), and therefore, the Si(001)–Ti (0001) structure is more inclined to delaminate.

The structure and corrosion resistance of anodized AA2099-T83 Al-Cu-Li alloy after layered double hydroxides (LDH) sealing and hot water sealing (HWS) were studied using scanning electron microscopy (SEM), X-ray diffraction, electrochemical impedance spectroscopy (EIS) and neutral salt spray test (NSST). Particularly, the corrosion resistance of the LDH-based coating system with reduced anodic film thicknesses was compared with that of the normal HWS-based coating system. It was found that LDH could be formed over the surface and within the pores of the anodic film within 30 min. With other conditions the same, the LDH-sealed alloy passed 1000 h of NSST without evident localized corrosion, contrasting with the HWS alloy, which showed severe localized corrosion after NSST for 120 h. Further, when the anodic film thickness was reduced from 3.7 to 1.3 μm, the LDH-sealed alloy still showed much better corrosion resistance than the normal HWS alloy. This work clearly demonstrates that it is possible to obtain high corrosion resistance for the anodized AA2099-T83 Al-Cu-Li alloy at much reduced anodic film thickness.

The hot rolling microstructures and textures were strongly influenced by the prior heat treatments. Various prior heat treatments were utilized to investigate the effects of precipitates on microstructure and β-fiber texture after hot rolling. For the microstructure, the extent of planar slips strongly affects the hot rolling microstructure. Shear events of δ′ particles resulted in massive shear bands, which were the consequence of extensive planar slips. T1 platelets and T2 rods would homogenize the dislocation slips, resulting in a homogenous microstructure. The abnormal microstructure in overaged specimens was ascribed to successive work softening in the precipitation free zones (PFZs). With respect to hot rolling texture, the kind of precipitates in the matrix affected the intensities and locations of the β-fiber tube in Euler space, especially in the section between Copper and S orientation.

The erosion behavior of a QAl9-4 alloy as a ship propeller material was investigated. The effects of the solution, the impact angles and the sand content were considered. The test results demonstrate that the mass loss of the alloy in 3.5 wt% NaCl solution is 1.35 times that in tap water, due to the corrosive effect of Cl−. The mass loss of the alloy increases as the impact angle increases up to ~ 30° and consequently decreases as the impact angle increases. Also, this feature is typical for the ductile metal behavior. At the impact angle of 0°, this feature is associated with the predominant erosion mechanisms, such as shallow plowing and surface fatigue; at 30°, this feature is micro-cutting, deep plowing and surface fatigue; and at 45°, it becomes indentation accompanied by extruded lips. The mass loss and surface roughness of the alloy increase as the sand content increases under the testing conditions.

The anodizing behavior of iron-containing intermetallic particles in AA2099 aluminum-lithium alloy and their effect on structure and corrosion resistance of the anodic film were investigated using electrochemical measurements and scanning electron microscopy. High-copper-containing Al-Fe-Mn-Cu particles (HCCPs) dissolved preferentially through dealloying at ∼ 0 V (vs. saturated calomel electrode) in a tartaric-sulfuric acid solution, at 22, 37 and 42◦C, leading to formation of copper-rich nanoparticle of 50–200 nm diameters. They dissolved completely under normal anodizing conditions, resulting in cavity defects of micrometer dimensions in the anodic film and sunken regions in the alloy substrate immediately beneath the dissolved HCCPs. Immersion testing of the anodized alloy in 3.5% NaCl solution for 24 h indicated that localized corrosion of the anodized alloy predominantly developed at the site containing dissolved HCCPs at the film/alloy interface. It is suggested that HCCPs play a critical role in controlling the corrosion resistance of the anodic film formed on AA2099 aluminum-lithium alloy.

The micro-scale abrasive wear behavior of TiZrNbTa (TZNT) alloy in Hank’s solution and distilled water was studied using the TE66 machine. The effect of load and sliding distance was considered. The results of experiments show that the wear volume of the TZNT alloy is increased with increasing distance because of the greater damage, but the wear volume is not present the same regularity as the increase of load due to the effect of several factors. Only three-body abrasive wear is present at the lower load, while the mixed wear mechanism includes three-body and two-body abrasive wears at the higher load. Through observation, the wear appears under the same sliding distance at various simulated body fluids. The wear appearance is related to the wear mechanism. For wastage map, under the conditions of this paper, the majority of the area is medium wastage, the rest is low wastage, and there is no high wastage. The wastage map is related to the wear volume of the alloy under different conditions.

Localized corrosion in an AA2099-T83 aluminum–lithium alloy has been correlated with localized plastic deformation (LPD) introduced by cold working. The high population density of dislocations in the slip bands associated with LPD promoted preferential precipitation of needle-shaped T1 (Al2CuLi) phase during artificial aging. Consequently, preferential attack of the electrochemically active T1 phase in corrosive environment resulted in selective corrosion of the bands, leading to the development of the characteristic morphology of narrow, parallel volume of corrosion. Copyright © 2015 John Wiley & Sons, Ltd.

The corrosion behavior of intermetallic particles and their role in the process of localized corrosion in AA2099-T83 aluminum–lithium alloy has been investigated. It was found that both high- and low-copper containing Al–Fe–Mn–Cu-(Li) particles could result in superficial pits on the alloy, and the high level of lithium in the high-copper-containing particles rendered them electrochemically more active than the low-copper-containing particles. Additionally, severe localized corrosion was found not to be directly related to the distribution of constituent particles in the alloy. The findings are not only relevant to the understanding of corrosion mechanism but also beneficial to the evaluation of thermomechanical treatments of the alloy.

A Cu–25Cr alloy prepared by vacuum induction melting method was treated by the high current pulsed electron beam (HCPEB) with pulse numbers ranging from 1 to 100. Surface morphologies and microstructures of the alloy before and after the treatment were investigated by scanning electron microscopy and X-ray diffraction. The results show that significant surface modification can be induced by HCPEB with the pulse number reaching 10. Craters with typical morphologies on the Cu–25Cr alloy surface are formed due to the dynamic thermal field induced by the HCPEB. Micro-cracks, as a unique feature, are well revealed in the irradiated Cu–25Cr specimens and attributed to quasi-static thermal stresses accumulated along the specimen surface. The amount of cracks is found to increase with the pulse number and a preference of these cracks to Cr phases rather than Cu phases is also noted. Another characteristic produced by the HCPEB is the fine Cr spheroids, which are determined to be due to occurrence of liquid phase separation in the Cu–25Cr alloy. In addition, an examination on surface roughness of all specimens reveals that more pulses will produce a roughened surface, as a result of compromising the above features.

In this study, friction stir processing (FSP) has been used to fabricate aluminum alloy 7075 based surface hybrid composite with a mixture of SiC and MoS2 reinforcement particles. The surface hybrid composite layer has been successfully fabricated at different content ratio of SiC and MoS2 particles by one-pass FSP. The SiC and MoS2 particles were distributed almost homogeneously over the nugget zone. The average Vickers hardness at nugget zone increased to about 190 at 100% SiC, and it decreased with increasing the MoS2 content ratio in reinforcement. The wear weight loss of the surface hybrid composite depended on the applied load and the relative content ratio of SiC and MoS2 particles. The surface hybrid composite of 75% SiC and 25% MoS2 showed superior wear resistance among all tested samples. The wear failure was attributed to the combination of the combination of abrasive wear and delamination.

The electrochemical corrosion behaviour of biomedical Ti–25Nb–3Mo–3Zr-2Sn (TLM) alloy was investigated in various simulated body fluids at 37±0·5°C utilising potentiodynamic polarisation and current–time curves. The Ti–6Al–4V (TC4) alloy was also investigated to make a comparison. The different simulated body fluids comprised of 0·9%NaCl saline, Hank’s and Ringer’s solution were employed. The effect of heat treatment on the electrochemical behaviour of the TLM alloy was also considered. It was discovered that all the test specimens were passivated once immersed into the simulated body fluids. It was also found that the TLM alloy has poorer corrosion resistance in Hank’s solution, due to the chemical composition of the Hank’s. After different heat treated, the TLM alloy had different phases and microstructure, and the corrosion behaviour of the TLM alloy was different. In this study, after the heat treatment of 760°C/1 h/AC+550°C/6 h/AC, the TLM alloy had better corrosion resistance. Owing to the c...

The micro-scale abrasion behaviors of surgical implant materials have often been reported in the literature. However, little work has been reported on the micro-scale abrasive wear behavior of Ti–25Nb–3Mo–3Zr–2Sn (TLM) titanium alloy in simulated body fluids, especially with respect to friction pairs. Therefore, a TE66 Micro-Scale Abrasion Tester was used to study the micro-scale abrasive wear behavior of the TLM alloy. This study covers the friction coefficient and wear loss of the TLM alloy induced by various friction pairs. Different friction pairs comprised of ZrO2, Si3N4 and Al2O3 ceramic balls with 25.4 mm diameters were employed. The micro-scale abrasive wear mechanisms and synergistic effect between corrosion and micro-abrasion of the TLM alloy were investigated under various wear-corrosion conditions employing an abrasive, comprised of SiC (3.5 ± 0.5 μm), in two test solutions, Hanks' solution and distilled water. Before the test, the specimens were heat treated at 760 °C/1.0/AC + 550 °C/6.0/AC. It was discovered that the friction coefficient values of the TLM alloy are larger than those in distilled water regardless of friction pairs used, because of the corrosive Hanks' solution. It was also found that the value of the friction coefficient was volatile at the beginning of wear testing, and it became more stable with further experiments. Because the ceramic balls have different properties, especially with respect to the Vickers hardness (Hv), the wear loss of the TLM alloy increased as the ball hardness increased. In addition, the wear loss of the TLM alloy in Hanks' solution was greater than that in distilled water, and this was due to the synergistic effect of micro-abrasion and corrosion, and this micro-abrasion played a leading role in the wear process. The micro-scale abrasive wear mechanism of the TLM alloy gradually changed from two-body to mixed abrasion and then to three-body abrasion as the Vickers hardness of the balls increased.

A Cu-10Fe alloy with magnetron sputtered Al films was irradiated by high current pulsed electron beam (HCPEB) with various pulse numbers, next changes of its microstructure and corrosion property were investigated. Compared with the initial sample, microhardness and corrosion resistance of the aluminized Cu-10Fe alloys after the HCPEB treatment are remarkably improved with increasing pulse numbers. This improvement could be attributed to formation of Al2Cu intermetallic compounds, occurrence of liquid phase separation and grain refinement in the surface layer of the Cu-10Fe alloy during the process of rapid remelting and solidification induced by the HCPEB treatment.

Tribology of bio-implants is a major limiting issue in materials selection of the appropriate implant for the appropriate patient activity level [1]. For example, for wear of replacement hip joints, wear caused by the sliding action of the bearing surface of the femoral head against the counterface occurs in synovial fluid. Hence, the major challenge of materials scientists in replacement of such materials is to optimize the wear resistance, minimize any potential tribo-corrosion interaction and adverse biocompatibility effects caused by such interactions and reduce wherever possible any adsorption of wear debris into the surrounding tissue. In Tribology, and in Aqueous Corrosion, various mapping methodologies[1-7] have been developed to characterize the various interactions. The wear map developed by Lim and Ashby [2] classifies the wear regimes at ambient conditions in terms of applied load and velocity, illustrating significant temperature rises and attendant corrosion reactions as a function of the tribological variables. The Pourbaix diagram[8] considers various transitions in terms of potential and pH, therefore presenting corrosion regimes as a function of the driving force of the electrochemical reaction and the hydrogen ion concentration. In tribo-corrosion, there is an extensive recent literature combing the concepts of both approaches to construct tribo-corrosion maps [2-8]. Despite such work, there has been very little work carried out until very recently[9] on the construction of tribo-corrosion maps for application to bio-tribo-corrosion environments. This is despite the fact that such maps may have significant application in optimizing materials for specific patient activity/mass combinations, all of which are important in selection of the most appropriate material combination in total replacement joint procedures. In studies of wear of candidate hip joint materials, it has been observed that particle concentration of wear debris can have an adverse effect on loosening of the joint, leading to osteolysis and potential revision of the replacement joint material [10]. In such cases, it is important to identify the effects of wear debris on the tribo-corrosion mechanism [12]. Assessing the effects of such particle concentrations with load is also of significance as it will indicate what dependency, if any, particle concentration has at various body masses as defined by variation of applied load. Hence, in this paper, the effect of applied load and abrasive concentration were assessed at a range of applied loads for Ti rotating against an inert Zirconia ball, in which abrasive particles of SiC were entrained in Hanks solution. The results were used to construct micro-abrasion-corrosion maps for application to biological environments. The significance of the bio-tribo-corrosion map in identifying mechanisms of wastage and the extent of synergy between the tribological and corrosion processes is addressed in this paper.

The in vitro degradation behaviour of Mg–Ca alloy was studied in the presence of albumin by in-situ observation, hydrogen evolution method and various electrochemical techniques. The corrosion and hydrogen evolution rates decreased and the formation of filiform corrosion induced by Cl � was also significantly inhibited due to the adsorption of albumin molecule. Moreover, the higher the concentration of albumin, the higher is the inhibitive effect. The EIS results further show that addition of albumin enhanced the charge transfer resistance and film resistance at the open-circuit potential. The synergistic effect of the negatively charged adsorbed albumin molecule and OH � has been discussed.

The erosion-corrosion behaviour of QSn6 alloy used as propellers in marine environment was evaluated by erosion-corrosion experiments with/without cathodic protection, electrochemical tests and scanning electron microscope (SEM) observations. The analysis was focused on the effect of flow velocity. The dynamic polarization curves showed that the corrosion rate of the QSn6 alloy increased as the flow velocity increased, due to the protective surface film removal at higher velocities. The lowest corrosion current densities of 1.26 × 10−4 A cm−2 was obtained at the flow velocity of 7 m s−1. Because of the higher particle kinetic energies at higher flow velocity, the mass loss rate of the QSn6 alloy increased as the flow velocity increased. The mass loss rate with cathodic protection was lower than that without cathodic protection under the same conditions. Also, the lowest mass loss rate of 0.7 g m−2 h−1 was acquired at the flow velocity of 7 m s−1 with cathodic protection. However, the increase rate of corrosion rate and mass loss were decreased with increasing the flow velocity. Through observation the SEM morphologies of the worn surfaces, the main wear mechanism was ploughing with/without cathodic protection. The removal rates of the QSn6 alloy increased as the flow velocity increased in both pure erosion and erosion-corrosion, whereas the erosion and corrosion intensified each other. At the flow velocity of 7 m s−1, the synergy rate (ΔW) exceeded by 5 times the erosion rate (Wwear). Through establishment and observation the erosion-corrosion mechanism map, the erosion-corrosion was the dominant regime in the study due to the contribution of erosion on the mass loss rate exceeded the corrosion contribution. The QSn6 alloy with cathodic protection is feasible as propellers, there are higher security at lower flow velocity, such as the flow velocity of 7 m s−1 in the paper.

The mechanical characteristics of the macro-arc oxidation (MAO) coating on Mg alloy AZ91 were examined by means of nano scratch tester. The corrosion and erosion corrosion behavior of AZ91 with and without MAO coating were investigated by using potentiodynamic electrochemical technique and micro-abrasion tribometer in simulated body fluids, respectively. The influence of HCO 3 − ions on the erosion corrosion was discussed. The results show that the coating and its substrate are in a pronounced bond. The MAO coating increases 1–2 orders of magnitude of the corrosion resistance of AZ91 alloy. HCO 3 − ions enhance the corrosion rates of the AZ91 alloys more significantly than the alloys with MAO coating. However, there exists an obvious passivation process of AZ91 without coating in the HCO 3 − solutions. Moreover, an MgCO 3 film formed in HCO 3 − containing solutions leads to an enhancement in micro-wear resistance. MAO coating deteriorates the erosion corrosion resistance of AZ91 alloy due to the formation of oxidation debris resulted from the broken MAO coating.

The fretting wear behavior of the AZ91D and AM60B magnesium alloys are investigated using a reciprocating fretting wear machine under dry conditions with different numbers of cycles, different normal loads, slip amplitudes and frequencies. The worn surfaces and wear debris were examined using scanning electron microscopy and optical microscopy in order to understand the predominant wear mechanisms of two magnesium alloys. The results indicate that the AZ91D alloy displays a lower friction coefficient and lower wear quantity than the AM60B alloy. The AZ91D shows a higher capability than AM60B in resisting crack nucleation and propagation. Both AZ91D and AM60B show similar friction and wear characteristics. The wear quantity increases with increasing normal load, but decreases with increasing frequency. The friction coefficient also decreases as the normal load is increased. Fretting frequency had little effect on the friction coefficient. In a long term, the fatigue wear and abrasive wear were the predominant wear mechanisms for AM60B and delamination wear, adhesive wear and abrasive wear for AZ91D.

The wear and electrochemical corrosion behavior of the biomedical Ti–25Nb–3Mo–3Zr–2Sn (TLM) titanium alloy was investigated in various simulated physiological solutions. Different simulated physiological solutions comprised phosphate-buffered solution (PBS), PBS with bovine serum albumin (PBS+BSA), and PBS with hyaluronic acid (PBS+HA) were employed. A potentiostat and a reciprocating friction and wear tester were used to study the wear and corrosion behavior of the TLM alloy. The influence of the chemical composition of the simulated solutions on the tribo-electrochemical behavior was considered by potentiodynamic studies under reciprocating friction and wear conditions. It was found that the corrosion tendency of the TLM alloy was the most obvious in PBS+HA under static corrosion condition, while it was just opposite with wear. Compared with static corrosion, the corrosion resistance of the TLM alloy was decreased with sliding conditions. The values of i corr were two orders of magnitude higher than those at static corrosion. This phenomenon shows that the wear accelerated corrosion. Under coexisting condition of both electrochemical corrosion and wear, the wear rate of the TLM alloy mutually influenced by both factors will be accelerated. Plastic grooves and deformation were observed on the worn surfaces of the TLM alloy by scanning electron microscopy (SEM). Through the observation of SEM, the tribological mechanism was a typical corrosive wear, and the main wear mechanisms were abrasive with adhesive wear under the interaction between corrosion and wear. The XPS results show that the passive films include the TiO2, ZrO2, Nb2O5, Mo2O5, and Sn2O3.

An abrasive wear test, based on the ball-crater technique, has been used to evaluate the abrasive wear resistance of TiN coatings in Hank’s solution. Microhardness measurements and scratch tests were carried out to characterize the mechanical properties of TiN coating under investigation. The influence of load, sliding distance and slurry concentration on wear volume was studied. Based on the surface analysis, the mechanism of micro-scale abrasive wear was also discussed. The results showed that the wear volume of TiN coatings was gradually increased with the increase of load, sliding distance and slurry concentration,and the wear volumes of TiN coatings were remarkably smaller than those of Ti6Al4V alloy in Hank’s solution. As the load was increased, there was a transition of wear mechanism from mixed abrasion or three-body abrasion to two-body abrasion, however, the wear mechanism was transformed from two-body abrasion to mixed abrasion or three-body abrasion when slurry concentration and sliding distance were increased.