Effect Of Substrate Microstructure Research Articles

Effect of substrate microstructure on corrosion resistance of cast and forged anodised 6082 Al alloy

This work addresses the effect of the surface morphology of a 6082-aluminium alloy on the characteristics of the anodic layer generated by an anodising process using two current densities. The samples tested were horizontal direct chill (HDC), vertical direct chill (VDC) cast billets, and the same material after forged + T6 ageing treatment. Samples were anodised in a mixed citric acid‑sulphuric acid electrolyte using 0.5 A⋅dm−2 and 1.5 A⋅dm−2. D.C. current densities. The protective character of the oxide layer was studied by electrochemical impedance spectroscopy (EIS) in 0.1 M NaCl solution.Microstructural characterisation revealed that the microsegregation and forging processes have a significant effect on the growth of the oxide layer as well as on the optimum anodising conditions. The EIS study showed that the corrosion protection provided by the oxide layer on Al6082 alloy was strongly affected by the manufacturing process, with thinner oxide layers obtained for cast billets. Heat treatment and forging homogenise the microstructure, which positively affects anodising and modifies the growth rate and thickness of the oxide layer. This effect makes obtaining a thicker oxide layer with good corrosion protective properties possible by using lower current densities for forged samples.

Effects of Substrate Microstructure and Chemical Composition on Liquid Metal Embrittlement in Galvanized 3rd Generation AHSS

Extensive efforts have been undertaken worldwide to develop new high strength steels with substantial fractions of retained austenite, for lightweight automobile manufacturing and other applications requiring improved combinations of strength and formability. These “3rd Generation” Advanced High Strength Steels (AHSS) are being implemented, and spot-welding has been found to present new challenges for these steels when Zn-based corrosion resistant coatings are involved, wherein zinc liquid metal embrittlement (LME) can occur. Some recent work is highlighted here that was designed to examine the separate effects of prior microstructure and alloy composition on LME sensitivity. LME behavior was assessed by comparing hot-ductility of steels with and without a Zn coating tested under conditions simulating spot-weld thermal cycles. Effects of prior microstructure on LME susceptibility were assessed with a single AHSS alloy composition, using annealing modifications to produce martensitic, Q&P, TBF and dual-phase substrates. The dual-phase steel exhibited less sensitivity to LME, perhaps because the Zn penetration and cracking are unable to follow (prior) austenite boundaries in this microstructure. With respect to alloy composition, carbon and manganese variations did not lead to noticeable effects on LME sensitivity, while silicon clearly leads to increased LME sensitivity. Addition of 1.3 wt. pct. aluminum to a 0.5 wt. pct silicon-containing AHSS steel further increased LME sensitivity at some test temperatures. The effects of alloying are interpreted in terms of the propensity to form an intermetallic reaction layer that consumes liquid and physically separates the substrate and liquid zinc.

Effect of Substrate Microstructure and Hydrophobicity on Ag Gas Diffusion Electrodes for Electrochemical CO2 Reduction

Electrochemical CO2 reduction (CO2RR) is a very promising way to convert detrimental CO2 emissions into sustainable fuels and chemicals, and move us closer to a circular economy.1 To compete with traditional fuel/chemical production routes, we need to develop electrocatalysts that are highly active, selectivity towards a desired product, and stable. Thanks to the use of gas diffusion electrodes (GDEs) that provide gaseous CO2 close to the catalyst, high activities can be achieved.2,3 However, product selectivity and stability must still be improved before practical application. An emerging strategy in this regard is to control the local environment surrounding a catalyst, i.e. the concentration of the various products and reagents therein.4 In this work, we achieve such control by varying the microstructure of substrates later used to fabricate GDEs by Ag deposition. By systematically studying the CO2RR performance, we observe a clear correlation between the pore size of the GDEs and their product selectivity, stability, and even resilience to Cu impurities.5 We rationalize it with the different effective hydrophobicity of the GDEs, which control the extent of electrolyte penetration within the electrode and depends on both substrate chemistry and pore size. We show that a higher effective hydrophobicity correlates with higher Faradaic efficiency towards carbon monoxide production (FECO up to 95 % at 100 mA/cm2) and longer stability (~100 % retention after a 1 hour electrolysis at 100 mA/cm2). These results show the importance of the substrate's microstructural properties in GDE for CO2RR, and highlight a new strategy to achieve control over selectivity and stability of these electrodes.

Influence of Hard Anodizing on the Mechanical and Corrosion Properties of Different Aluminum Alloys

Hard anodizing of different aluminum alloys 2014-T3, 6061-T6, and 7075-T6 is conducted in sulfuric acid electrolyte at a temperature of − 5 °C and current densities of 1.6 to 2.8 A/dm2 for 30 to 60 min. The effect of substrate microstructure on the mechanical properties, corrosion resistance, and morphology of the hard anodic layers is investigated. Electrochemical technique, thickness, hardness, and abrasion testing devices are used to test the corrosion and mechanical properties of hard anodic layers. The morphology and nanostructure of the anodic film are observed by SEM. The results show that the 7075-T6 (Al–Zn–Mg–Cu) aluminum alloy has the highest hard coat thickness, hardness, and abrasion resistance. The Fe, Si intermetallic phases present in 6061 Al alloy hinder the oxide growth. The oxide layer formed on 2014 Al alloy has the lowest thickness, hardness, abrasion resistance, and corrosion resistance due to the high content of copper.

Superheated slurry cast 7075 aluminum alloy for anodizing applications

Anodic oxide layers formed on three cases of 7075 Al alloy substrate were investigated. The effects of substrate microstructure on the anodic oxide layer were assessed. The 7075 Al alloy substrates were produced by superheated slurry casting of Gas Induced Semi-Solid (GISS) type, from initial solids fractions of 9% (SSM3), 22% (SSM10), and 33% (SSM20). They varied in the number and size of secondary phase particles in the microstructure. The anodizing was performed in sulphuric acid solution sealed by hot water. The thickness of the anodic oxide layer was similar (∼13 μm) across all cases. The SSM3 had rather linear substrate/oxide interface, while the other cases had irregular interfaces disturbed by the secondary phase particles. The SSM3 had smaller secondary particles embedded in the anodic oxide layer than the other cases that had higher secondary phase fraction. This resulted in the lowest hardness of the anodic oxide layer for the SSM3 case.

Effects of substrate microstructure on biomimetic unit properties and wear resistance of H13 steel processed by laser remelting

To improve the service life of H13 steel with different substrate microstructures, the bionic coupling units of H13 steel were manufactured by laser remelting on four types of heat treatment surface. The differences and regularities in the size, microstructure, grain size, hardness and wear resistance of the units were compared and discussed. The results demonstrated that the cross-sectional area and grain size of the units were enlarged with the increase of austenite nucleation ability of the substrate microstructure, but the degree of micro-hardness improvement was reduced. Meanwhile, its micro-hardness and the corresponding wear resistance were improved to varying degrees. In particular, the improvement of the annealed state was the highest, as the micro-hardness and wear resistance were enhanced by 165.57% and 39.10%, respectively.

Effect of Micropillar Spacing and Temperature of Substrate on Contact Angle Dynamics

ABSTRACTContact angle dynamics of droplets deposited on a structured surface were studied in this work and the effects of substrate microstructure and temperature were investigated. Microstructures consisting of uniformly-sized, cubic micropillars with varying pillar spacings were constructed by microfabrication. Droplets (of the order of tens of microlitres in volume) were deposited on these surfaces and dynamic contact angles were observed using various techniques. Advancing and receding contact angles were measured using tilting of the surfaces or by injection and aspiration of fluid from a horizontal droplet by syringe. Droplets on these surfaces appeared to be mainly in the Wenzel state. Contact angle hysteresis was obtained as a function of pillar spacing or, equivalently, surface roughness. Depinning force was deduced and a linear dependence on maximal three phase contact line was found. The techniques of tilting the surface on which the droplet was deposited and uniformly increasing and reducing the volume of the droplet via the syringe both gave the same contact angle hysteresis for a given micropillar spacing. The effect of temperature was then assessed using a heated tilting plate. Contact angle hysteresis was found to increase with temperature. Further work to elucidate mechanisms governing this dependence will be undertaken.

Effect of substrate microstructure on fatigue strength characteristics in flake graphite cast iron for automobile engine component

Effect of substrate microstructure on fatigue strength characteristics in flake graphite cast iron for automobile engine component

Effectiveness of tetra-ethyl-ortho-silicate (TEOS) consolidation of fired-clay bricks manufactured with different calcination temperatures

Tetra-ethyl-ortho-silicate (TEOS) consolidation is a promising technique; however, the effects of substrate microstructure and mineralogy on the TEOS performance have not been systematically assessed; which is critical to improve consolidation efficiency. Clay bricks were manufactured in a variety of clay/kaolin proportions, calcination temperatures and treated with TEOS. by immersion. TEOS retentions between 4.9% and 5.9% were obtained, which increased surface hardness, compressive strength and flexural strength compared to non-treated specimens. Furthermore, consolidation reduced brick permeability and resulted in slight color variations. These improvements are explained by the deposition of consolidant in the pores and substrate–consolidant chemical interaction.

The Effect of Substrate Microstructure on the Heat-Affected Zone Size in Sn-Zn Alloys Due to Adjoining Ni-Al Reactive Multilayer Foil Reaction

The rapid release of energy from reactive multilayer foils can create extreme local temperature gradients near substrate materials. In order to fully exploit the potential of these materials, a better understanding of the interaction between the substrate or filler material and the foil is needed. Specifically, this work investigates how variations in local properties within the substrate (i.e. differences between properties in constituent phases) can affect heat transport into the substrate. This can affect the microstructural evolution observed within the substrate, which may affect the final joint properties. The effect of the initial substrate microstructure on microstructural evolution within the heat-affected zone is evaluated experimentally in two Sn-Zn alloys and numerical techniques are utilized to inform the analysis.

Effects of substrate microstructure on the formation of oriented oxide nanotube arrays on Ti and Ti alloys

The formation of nanotubular oxide layers on Ti and Ti alloys has been widely investigated for the photocatalytic degradation of organic compounds due to their excellent catalytic efficiency, chemical stability, and low cost and toxicity. Aiming to improve the photocatalytic efficiency of this nanostructured oxide, this work investigated the influence of substrate grain size on the growth of nanotubular oxide layers. Ti and Ti alloys (Ti–6Al, Ti–6Al–7Nb) were produced by arc melting with non-consumable tungsten electrode and water-cooled copper hearth under argon atmosphere. Some of the ingots were heat-treated at 1000°C for 12 and 24h in argon atmosphere, followed by slow cooling rates to reduce crystalline defects and increase the grain size of their microstructures. Three types of samples were anodized: commercial substrate, as-prepared and heat-treated samples. The anodization was performed using fluoride solution and a cell potential of 20V. The samples were characterized by optical microscopy, field-emission scanning electron microscopy and X-ray diffraction. The heat treatment preceding the anodization process increased the grain size of pure Ti and Ti alloys and promoted the formation of Widmanstätten structures in Ti6Al7Nb. The nanotubes layers grown on smaller grain and thermally untreated samples were more regular and homogeneous. In the case of Ti–6Al–7Nb alloy, which presents a α+β phase microstructure, the morphology of nanotubes nucleated on α matrix was more regular than those of nanotubes nucleated on β phase. After the annealing process, the Ti–6Al–7Nb alloy presented full diffusion process and the growth of equilibrium phases resulting in the appearance of regions containing higher concentrations of Nb, i.e. beta phase. In those regions the dissolution rate of Nb2O5 is lower than that of TiO2, resulting in a nanoporous layer. In general, heat treating reduces crystalline defects and promotes the increasing of the grain sizes, not favoring the process of nanotube nucleation and growth on the metallic surface.

Comparative analysis for corrosion resistance of micro-arc oxidation coatings on coarse-grained and ultra-fine grained AZ91D Mg alloy

By micro-arc oxidation (MAO) process in a silicate electrolyte, the oxide coatings were successfully formed on a coarse-grained casting AZ91D Mg alloy and an ultra-fine grained (UFG) one fabricated by equal-channel-angular-pressing (ECAP). The effect of substrate microstructure on morphologies and corrosion resistance of the MAO coatings on AZ91D alloys were investigated by scanning electron microscopy observation, immersion tests and electrochemical impedance spectrum (EIS) measurements. In comparison, the MAO coating on the UFG Mg alloy has lower corrosion rate and larger Rf value. Three factors enhance the corrosion resistance. The first is the MAO coating with uniform size and distribution of micro-pores due to homogenous micro-arc discharge. Secondly, the number of open holes decreases due to the finer β-phase after ECAP process. The most important one is the higher compactness and thickness of the coating on the UFG Mg alloy. It implies that the MAO coatings have a great potential in surface protection of UFG Mg alloys.

Effect of substrate microstructure on the misorientation of a-plane ZnO film investigated using x-ray diffraction

( 11 2 ¯ 0 ) ZnO (nonpolar a-plane ZnO) films were grown on (11¯02) Al2O3 (r-plane sapphire) substrates by single-source chemical vapor deposition. The misorientation in the film was investigated in detail using x-ray diffraction techniques, including 2θ-ω scan, reciprocal space mapping (RSM), and double- and triple-crystal x-ray diffraction analysis. 2θ-ω scan and RSM measurements suggest that ZnO film grows on r-plane sapphire substrate epitaxially along the [112¯0] orientation, and the (112¯0) plane of the ZnO film tilts with respect to the (11¯02) plane of the substrate. RSM measurement for sapphire substrate shows that the diffraction intensity distribution around (22¯04) reciprocal lattice point presents a curved band along the 2θ-ω scan direction, which can be attributed to a strained layer (or a lattice distortion layer) at the substrate surface. Double- and triple-crystal x-ray diffraction measurements imply that anisotropic mosaic exists in sapphire substrate. The strained layer and tilt mosaic in sapphire substrate may be the important reasons for the tilted growth of the (112¯0) plane of a-plane ZnO film relative to (11¯02) plane of the Al2O3 substrate.

Direct observations and analysis of the spallation of alumina scales grown on PM2000 alloy

The spallation during cooling or thermal cycling of alumina scales grown at high temperature on PM2000 alloy is directly observed and recorded using CCD cameras. This simple and direct method permits to determine easily and accurately the scale spallation kinetics. In addition, it provides many insights on the spallation mechanisms and processes and their evolution as well as on the effect of substrate microstructure on spallation.

Characteristics of surface remelted hardfacing spheroidal graphite cast iron using the plasma transferred arc process

The plasma transferred arc (PTA) process was used to obtain a 2–5 mm thickness remelted hardfacing layer on the spheroidal graphite cast iron surface. Cementite structure can be observed on the surface layer, exhibiting a significantly high hardness due to rapid solidification. The composition of 3.54 wt pct carbon and 2.48 wt pet silicon remains fixed throughout the PTA surface remelting experiment. To study the effect of substrate microstructure on the remelted hardfacing layer, experimental parameters including spheroidal graphite nodule count and the microstructure of matrix are conducted.Experimental results confirm that the remelted hardfacing layer is accompanied by a large amount of Fe3C eutectic cementite. If the PTA remelting input current is increased, the volume fraction of eutectic cementite tends to decrease, subsequently decreasing the hardness. An increased spheroidal graphite nodule count of the substrate tends to decrease the hardness of the remelted hardfacing layer. The substrate with ferritic matrix shows increased hardness over a pearlite structure. Furthermore, while the impact angle is fixed at 30°, the erosion wear resistance increases with the increasing hardness of the remelted hardfacing layer, but this tendency is contrary when the impact angle is fixed at 90°.

Effects of substrate microstructure on the magnetic anisotropy of sputtered cobalt alloy film

The magnetic properties and crystalline structure of Co alloy film deposited on a regularly corrugated substrate have been studied. Microscopic grooves are lithographically fabricated on InP substrates. In-plane anisotropy energy is 4–5×10 4J/m 3. The magnetic anisotropy is affected by the crystallographic orientation and the microscopic shape of the corrugated Co alloy film.

Influence of substrate structure on the growth of hydrogenated amorphous silicon studied by i n s i t u ellipsometry

Using in situ ellipsometry as a probe, the effect of substrate microstructure on the growth habit of high-quality hydrogenated amorphous silicon (a-Si:H) has been studied. An understanding of the growth process is important when combining a-Si:H with other materials in thin-film multilayer devices. The present study concentrates on cases where a-Si:H of different microstructure, microcrystalline Si:H (μc-Si:H), and single-crystal Si are used as substrates. The a-Si:H top film is grown under identical conditions on each substrate material and pseudo-dielectric-function trajectories are collected during growth. These trajectories have been applied to characterize the bulk and interface structure and the evolution of surface roughness layers during growth. For the same deposition conditions, a range of growth patterns is observed, depending on the structure of the substrate.