Alloy Additions Research Articles

Microstructure Evolution and Mechanical Properties of a TiAl Alloy Modified by High-Entropy Alloy Additions

Microstructure Evolution and Mechanical Properties of a TiAl Alloy Modified by High-Entropy Alloy Additions

Morphologically controlled synthesis, characterization, and applications of molybdenum oxide (MoO3) nanoparticles

AbstractMolybdenum nanoparticles are used as additives in alloys for various applications, such as or in corrosive or high‐vacuum environment. Their properties are completely different than the properties in their bulk. Molybdenum nanoparticles were prepared by hydrothermal technique. MoO3 synthesized nanoparticles were characterized by UV‐visible spectroscopy, SEM, TEM, and XRD. MoO3 had shown its maximum adsorption at wavelength 560 nm. Surface morphology of synthesized MoO3 was studied by using SEM, which showed that MoO3 nanoparticles have shown outgrowth at the edges of strands, while grain size, shape, and distribution was confirmed with TEM, which revealed that the synthesized nanoparticles are fiddle and thin in nature and these particles are made of joint nanosheets. Furthermore, the structure elucidation of synthesized nanoparticles was done by using the XRD calculations, which confirmed that the synthesized particles are MoO3 without impurities. Moreover, MoO3 nanoparticles can be used for photocatalytic properties and biological application.

The effect of varying nickel concentration on the hydrogen pickup fraction and corrosion resistance in Zircaloy-4

Zircaloy-4 samples with various levels of Ni content (0–483 wt. ppm) were exposed in autoclave for up to 2800 days. Samples were destructively and non-destructively measured to determine the weight gain from oxidation and hydrogen contents to better understand the role hydrogen has in increasing oxide growth rates and to study the effect of Ni on the mechanism of hydrogen pickup in Zr alloys. Overall, additions of Ni lead to significantly higher hydrogen pickup of the alloy. As observed previously, at higher weight gains, a small decrease in hydrogen pickup fraction is observed for all alloys tested (Zircaloy-4 with and without Ni). A small beneficial effect of Ni was observed on corrosion rate when controlling for the amount of hydrogen in the material, which potentially indicates that if hydrogen content were controlled via other means (e.g., volume or other alloy additions) Ni may improve corrosion resistance of the material. Results generally support published density functional theory (DFT) hypotheses that point to an increase in hydrogen solubility or catalysis of surface reactions as the mechanism by which Ni increases hydrogen pickup. Data or future corrosion testing of alloys with Ta, V, or Ti additions could further support or refute these theories by testing aspects of the proposed mechanisms.

Eutectoid phase transformation in U-Mo-X alloys

U-Mo based alloys undergo eutectoid phase transformation where high temperature γ-U decomposes into α-U and U2Mo phases. In the present study, eutectoid decomposition of γ-U phase into α-U and γ’-U2Mo phases in three U-9 Mo, U-8Mo-1V and U-8Mo-1Zr alloys was examined. By carrying out detailed crystallographic analysis of the eutectoidally decomposed products of the U-9Mo alloy, orientation relationships between the parent and product phases were determined. Using the orientation relationship, lattice correspondence among the parent and product phases has been worked out. This lattice correspondence has shown that the product lattices could be derived from the (110) planes of the parent γ-phase wherein the (110) plane of the γ-phase can be converted into the (001) plane of the α-phase and (110) or (103) planes of the γ’-phase. However, during transformation, occurrence of strains within lattice could be one factor through which the kinetics of the phase transformation or morphology of daughter products could be controlled. Based on this idea, ternary alloy additions with different sizes of the solute atoms (Zr or V) have been carried out. This allowed us to manipulate the strain associated with the transformation which was reflected in terms of changes in the width of product phase lamellae.

Multiple strengthening via high-entropy alloy particle addition in titanium matrix composites fabricated by spark plasma sintering

The strong interface bonding of particle reinforced metal matrix composites has been a longstanding puzzle. Unlike the existing titanium matrix composites (TMC) processed, which are mainly reinforced by ceramic particles, this work investigates the in-situ triggered alloying via high entropy alloy (HEA) addition, which promotes multiple strengthening to the metal matrix. The effects of HEA content on the microstructure evolution, mechanical properties, void growth mechanism, sintering model and underlying strengthening mechanism were investigated. The results show that the enhanced diffusion effect in the diffusion region leads to the formation of a multiphase structure composed of an FCC solid solution and a σ phase. In addition, with the addition of HEAs content, the yield strength and hardness values of all composites were higher than those of unreinforced Ti6Al4V (TC4). The obtained composite reinforced with 4.5 wt% HEA achieves an unprecedented tensile elongation to failure of 8.8% and a high ultimate tensile strength of 1150 MPa. The enhancement of the strength is attributed to the combined effects of grain refinement strengthening, load transfer strengthening and dislocation strengthening.

Short range ordering improves elastic properties of Mo additive W-Re solid solution: A first principles investigation

Re can significantly improve the ductility of W, while it is prone to form clusters and intermetallic phases, leading to instability and brittleness of W. To explore better ways to inhibit the adverse effects, we explored combined effect of Mo and alloying order on the phase stability and mechanical properties of W-Re alloys by using the first principles method. It is found that the short range ordered (SRO) W-Re structure is softer than that of random and ideal solid solution alloys. While SRO W-Mo-Re structure possesses higher stability and strength than those of random distributed alloys. The SRO W-Mo-Re structure can promote the coherent bonding enhancement between W, Mo and Re. This study shed light on better design of alloy additions and control of alloy orders to modulate the softening and strengthening properties in W and W-Re alloys, especially to reduce the hardening and instability induced by Re rich clusters.

Production of Ductile Iron Using Inside-Mold Treatment Technique

Ductile Cast Iron is a widely used cast iron. Ductile iron applications are used in various sectors of modern mechanical industries. Ductile iron has wide uses in the field of car industry, military industries, agricultural equipment, construction and mines. The production of ductile iron faces many technical difficulties in our local factories due to the difficulty in providing equipment and technologies for its production by common methods. In this study, we resorted to applying one of the modern methods in the production of ductile iron, which is the treatment process for the molten iron in the sand mold. Magnesium alloys were added inside the sand mold within the casting stream and in the casting cavity for casting production. Specific weights were added and experiments were performed to determine the fusible chemical composition appropriate for preparing ductile cast iron. The study proved that adding magnesium alloys inside the sand mold, whether inside the mold cavity or in the casting channel, is both a successful method for producing ductile iron alloys. It is possible to produce different types of ductile iron by controlling the ratio of alloy additions to the molten metal content during casting.

Effect of Cold Work, Ageing on Hardness and Ultimate Tensile Strength of Microalloyed Steel

Recent past witnessed the widespread use of High Strength Low Alloy steels in several structural applications, including pressure vessels, line-pipe transportation of crude oil in the oil industry and many more. API X-65 grade is widely used as a promising material for line-pipe applications in the oil industry. HSLA X-65 plate steels are produced by normalising, Controlled Rolling (CR), Direct Quenching & Tempering (DQT) or Quenching & Tempering (Q&T) techniques. These steels are characterised by their low carbon concentration while maintaining low alloy additions. Micro alloy additions such as V, Ti, and Nb provide substantial precipitation strengthening effect. Strengthening, hardness and microstructural examinations are conducted in all the stages to ascertain X-65 HSLA steel's ageing behaviour.

Review on Corrosion studies of Heat Treated Al-Si Alloy

Heat-treated Al-Si alloys are widely used in the automotive, military, marine, electrical, food and chemical industries. This alloy exhibits high-strength properties used in corrosion-resistant homes. However, this alloy has low mechanical properties and a large granular structure when cast. The properties of aluminium alloys depend primarily on the microstructure. It is very important to achieve a smooth structure. The formation of fine and equivalent grains depends primarily on the amount of hardening, the addition of basic alloys (grain cleaners), the mixing and processing of alloys. Aluminium alloys are an important component of light metals used in industry. Al-Si alloys are essential for automotive, aerospace, marine and engineering applications. Al-Si alloys have excellent physical and mechanical properties. These alloys offer low weight, excellent corrosion resistance, easy machining, heat treatment, excellent casting ability and excellent machining performance. The mechanical properties of these alloys depend primarily on the size, shape and distribution of Si and Al particles. Al-Si alloy produces coarse α-Al dendrites and shark eutectic silicon. Fine structures are known to provide good mechanical properties and reduce casting defects. During the casting process, a fine-grained structure can be obtained by adding a lower alloy to the melt.

FSW on AA5083 H-111 and AA5754 H-111 dissimilar plates with scandium intermetallic layer

This study studied the effects of Al-4.5Mg-0.3Sc alloy addition to the weld nugget of friction stir weldments. The scandium (Sc) is introduced into the weld nugget zone in the form of an interlayer with varying thicknesses (0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm) between the base metal plates during the friction stir welding (FSW) process. FSW is then carried with and without a scandium interlayer to study the effect of scandium additions on the weld nugget. The tensile tests were conducted on all the FSW samples and the optimum thickness of the scandium interlayer was determined from the interpretation of the results. The FSW sample joint produced with the Sc interlayer thickness of 1.5 mm exhibited the highest ultimate strength due to the formation of a smaller number of precipitates. The addition of Sc increased the joint efficiency from 38.9% to the maximum of 63.8%. Then the micro Vicker’s hardness (HV) survey was conducted on the FSW samples to determine the strength of the joint and it was found that the maximum HV was found as 104 HV on the AA5083 side. The welded samples are then characterized using the scanning electron microscope to discuss the microstructural changes on the weld due to the addition of scandium.

Effects of Process Parameters on Microstructure and Mechanical Properties of Semi-Solid Al-7Si-0.5Mg Aluminum Alloy by Gas Induced Semi-Solid Process

Al-7Si-0.5Mg aluminum alloy semi-solid slurry with good spherical grains was prepared by gas induced semi-solid process (GISS) and the effects of both holding time and medium alloy addition on the microstructure of the semi-solid slurry were investigated. These two parameters have a great influence on the solid fraction, the size and the sphericity of the grains. With holding time increased from 85 s to 270 s, the solid phase fraction of the semi-solid slurry decreased from ~0.77 to ~0.67, the average grain size increased from ~95 μm to ~225 μm and the average shape factor decreased from ~0.80 to ~0.33. When medium alloy addition varied in the range of 0.5–2.0 wt%, a better slurry microstructure was obtained at about 1.5 wt%. Compared with the conventional liquid die-casting, the semi-solid die-casting improved the mechanical properties of tensile bars; yield strength, tensile strength and elongation of tensile bars reached ~240 MPa, ~307 MPa and ~8.8% after heat treatment, respectively. In conclusion, GISS process can prepare the semi-solid slurry with uniform and round microstructure, and the semi-solid die-casting can improve mechanical properties of Al-7Si-0.5Mg aluminum alloy.

Thermokinetic stabilisation of nanocrystalline Cu by ternary approach

ABSTRACT Nanocrystalline alloy design with the synergistic contribution of ‘thermodynamic’ and ‘kinetic’ stabilisation mechanism leads to much superior microstructural stabilisation at elevated temperatures. Ternary Cu98.5W1Zr0.5 (at. %) alloy, synthesised by mechanical milling under cryogenic temperature followed by consolidation through hot pressing at 550°C, has been examined to access the potential of their concurrence. A meager drop in hardness (∼0.5 GPa) confirms the stability of the alloy up to 800°C. The effect of alloy addition has been studied in terms of microstructure alteration, measured by X-ray diffraction, transmission electron microscopy, and Molecular dynamics (MD) simulation. In addition, the shear punch test (SPT) has been employed to assess the mechanical property of the consolidated alloy. Results suggest that the current approach provides a framework en route to designing bulk nanostructured alloys adapting the bottom-up method.

Convolutional Neural Network‐Based Method for Predicting Oxygen Content at the End Point of Converter

The main factor affecting the cleanliness of steel is inclusions, most of which are deoxidation products. The greater the oxygen content fluctuation at the converter's end point, the more unstable the inclusion control. A large amount of charging, operation, and sampling data is collected during the converter smelting, but it is not fully utilized, and the deoxidizing alloy addition still relies on manual experience. Herein, the representative convolutional neural network (CNN) of deep learning is adopted, and the number of convolutional layers, convolutional kernel size, and the number of convolutional kernels are optimized to establish the best prediction model of the converter end point. Its root mean square error, mean absolute error, and mean absolute percentage error are 35.29%, 25.59%, and 7.30%, respectively, which are superior to the back propagation neural network. This CNN prediction model uses 1300 sets of preprocessed data containing 23 indicator variables, of which 1200 sets of data are used for training and 100 sets for model validation. Within the ±50 ppm error scope, the model prediction hit rate can reach 87%, and when within the ±70 ppm error scope, the hit rate is 93%.

Facile and cost-effective approach to additively manufacture crack-free 7075 aluminum alloy by laser powder bed fusion

It is an often challenging but essential issue to develop a facile and cost-effective approach to additively manufacture crack-free and high-strength Al alloys for their wider commercial applications. However, efficient synergistic combination of advanced technology and material development is hardly likely to achieve without considering the extreme processing conditions during additive manufacturing. In this study, the addition of 4 wt% Ti-6Al-4V (TC4) alloy powders, the most commercially used Ti alloy powders, into the laser powder bed fusion (L-PBF) of 7075 Al alloy was performed and experimentally verified to be capable of eliminating the hot cracks while substantially refining the grains. The as-printed sample was crack-free and had a high relative density of up to 99.95%. Synergy effect of the in-situ formation of Al3(Tix,V1−x) particles that act as the heterogeneous nucleation sites, and the solute effect of the elements Ti and V that possess a high grain growth restriction factor (Q value) in Al matrix can efficiently control the grain growth. After a direct ageing treatment, the resultant alloy displayed an excellent combination of the high ultimate tensile strength (441 ± 3 MPa) and large plasticity (10.1 ± 0.4%). Our work brings new insights between the grain refinement and crack elimination of additively manufactured Al alloys through addition of commercial Ti alloys, benefiting the tailoring and development of new crack-free and dense high-strength Al alloys for L-PBF.

Impact of boron as an alloying addition on the microstructure, thermo-physical properties and creep resistance of a tungsten-free Co-base γ/γ′ superalloy

While boron is added to many structural alloys primarily as a grain-boundary strengthener, it has myriad other implications on the microstructure and thermophysical properties of these alloys. In the present study, we report these effects by varying boron addition in the range of 0.02 at.% to 0.8 at.% on the microstructure, thermo-physical properties and the creep resistance of tungsten free, γ/γ′ base Co–30Ni–10Al–5Mo–2Ta–2Ti (at.%) polycrystalline superalloy. Without boron addition, the plastic strain during creep at 850 °C is primarily accommodated through grain-boundary decohesion, often enhanced by severe oxygen attack along the grain boundaries. The addition of boron alleviates the poor grain-boundary cohesivity while inhibiting internal oxidation. An increase in the solvus temperature with boron addition was found, leading to an increase in the high-temperature capability of this alloy (∼40 °C). However, a concurrent decrease in the alloy's melting point has been observed. Coupled with improved grain-boundary cohesivity and larger grain size, improvement in creep resistance by almost an order of magnitude could be achieved. While at low amounts of boron (0.02–0.08 at.%) borides do not form, indicating solid solubility of boron within the bulk alloy, at high boron contents (0.2–0.8 at.%), Co and Mo rich boride forms primarily along the grain boundaries. These borides are surrounded by a distribution of fine secondary γ′ precipitates around them. In contrast, borides in Co–Al–W alloys promote precipitate free zones (PDZ), causing deterioration of mechanical properties. The beneficial effect of boron along grain-boundaries, both in elemental form and in the form of borides, has been highlighted in the present study which paves way for optimizing boron addition in other alloys of this class.

Effect of Ti-Hf-Zr-Cu-Ni high entropy alloy addition on laser beam welded joint of Ti2AlNb based intermetallic alloy

• In this study, LBW of Ti-22Al-27Nb was experimented through addition of an interlayer of the filler, Ti-Hf-Zr-Cu-Ni HEA, into the joint and a comparison between the LBWJs of Ti-22Al-27Nb either prepared with or without addition of the filler was established through microstructural analysis by corelating its impact on mechanical properties at room temperature. Followings are the highlights of this experimental work. • The addition of Ti-Hf-Zr-Cu-Ni HEA into FZ of LBWJ of Ti-22Al-27Nb activated heterogenous nucleation due to difference of chemical composition between the BM and the filler, resultantly, fine grained B2 phase with greater fraction of HAGBs was evolved in the FZ. Grain refinement and higher misorientation angle between GBs in the FZ contributed an increase in hardness, tensile strength and percentage elongation of HEA adulterated LBWJ of Ti-22Al-27Nb. • The average hardness of the FZ (343.5 HV) and UTS (1062 MPa) of the HEA added LBWJ was found in close agreement with that of BM, 345 HV and 1060 MPa, respectively. • The percentage elongation of the joint, prepared with an interlayer of HEA, was measured up to 11.2%, which was 83.6% of the BM. • The LBWJ of Ti-22Al-27Nb, prepared with the addition of HEA, fractured from the junction of FZ and HAZ in a ductile mode while the LBWJ prepared without addition of Ti-Hf-Zr-Cu-Ni filler was ruptured from FZ in quasi-cleavage mode. Ti 2 AlNb based intermetallic alloys, a potential competitor for next-generation super alloys, are susceptible to high-temperature embrittlement due to nucleation of a metastable single B2 phase in the fusion zone (FZ) during laser beam welding (LBW). In this study, a high entropy alloy (HEA), Ti-Hf-Zr-Cu-Ni, was self-developed and introduced as an interlayer into laser beam welded joint (LBWJ) of Ti-22Al-27Nb to analyze its impact on the evolution of microstructure in the weld zone (WZ) and subsequently on joint performance. Microstructural examination was carried out through electron probe micro analysis (EPMA), electron backscattered diffraction (EBSD) analysis, high-resolution scanning transmission electron microscopy (HRSTEM) comprising bright field (BF), selective area electron diffraction (SAED) and high angle annular dark-field (HAADF) imaging. Addition of the HEA into FZ of LBWJ triggered heterogenous nucleation during solidification, resultantly, fine-grained B2 with a greater proportion of high angle grain boundaries (HAGBs) was developed. FZ of Ti-22Al-27Nb LBWJ, prepared with an interlayer of HEA, was composed of planar, cellular, columnar and equiaxed dendritic grains; a solidification mode which was different from that observed in LBWJ prepared without adulteration of the HEA. The impact of heterogenous nucleation during epitaxial solidification on mechanical properties was established through micro vickers hardness mapping and tensile test, conducted at room temperature. The average hardness, 343.5 HV, in the FZ of LBWJ prepared with an interlayer of HEA, was compatible with that of base material (BM), 345 HV. The ultimate tensile strength (UTS), 1062 MPa, and percentage elongation, 11.2%, of the HEA tempered LBWJ were found in close approximation with that of BM, 1060 MPa and 13.4%, respectively. A ductile mode of failure was observed during tensile test of the Ti-Hf-Zr-Cu-Ni supplemented LBWJ of Ti-22Al-27Nb, while quasi-cleavage mode of fracture was apparent in the joint of Ti-22Al-27Nb welded without addition of the HEA.

Effect of FeSi Alloy Additions and Calcium Treatment on Non-Metallic Inclusions in 304 Stainless Steel during AOD and LF Refining Process

Non-deformable inclusions are detrimental to the surface quality and mechanical properties of stainless-steel plates. Plant trials were conducted to investigate the effect of different ferrosilicon alloys and calcium treatment during argon oxygen decarburization (AOD) and ladle furnace (LF) refining on inclusions in Si-killed 304 stainless steel. The inclusions were examined by scanning electron microscope with energy dispersive spectrometer. The results show that both the contents of soluble aluminum in molten steel and Al2O3 in slag increase with the increase of aluminum content in FeSi alloy. The content of soluble aluminum in liquid steel could be limited to lower than 0.004% when using ultra-purity FeSi alloy. When the calcium wire addition is 2 m/t, inclusions are located in the low-melting-temperature region, and the inclusion rating of hot rolled plates is mainly C-class. Industrial application shows that, by decreasing the soluble aluminum content in liquid steel, decreasing the MgO and Al2O3 in slag in AOD, and applying low basicity refining slag as well as calcium treatment, the inclusions are low melting point silicates. The inclusion rating of hot rolled plates is mainly fine C-type with a small amount of class-A, and surface polishing qualification rate is increased from 17.8% to more than 88.7%.

Effect of Nd-Co on microstructure and magnetic properties of Nd-Ce-Y-Fe-B sintered magnets

The magnetic properties and microstructure of Nd-Ce-Y-Fe-B magnets with Nd-Co boundary additions (0, 1, 3, and 5 wt%) have been systematically investigated. The coercivity, remanence, and Curie temperature of the magnets showed to be all simultaneously improved with appropriate Nd-Co addition, especially, a significant coercivity increase of 15% accompanied with the remanence optimization was obtained at 3 wt% Nd-Co addition. The analyses revealed that the coercivity enhancement was attributed to the widened grain boundary width and the reduced magnetic exchange coupling between grains by the Nd-Co intergranular introduction. By designing the partial substitution, e.g. Co for Fe and Nd for Ce in matrix phase grains, the remanence improvement was achieved with the increased net magnetic moment, compensating the magnetic dilution brought by the extra alloy additions. Meanwhile, the Curie temperature of the magnet was improved with the weakened negative interaction. The combined intrinsic and microstructural modification in this study provides new insights into the preparation of high-abundance magnets with high coercivity, high remanence, and excellent temperature stability.

The Effect of Ammonium Ions on the Corrosion Resistance of Zinc - Aluminium and Zinc - Aluminium - Magnesium Coated Steel

Galvanizing is the process of applying a protective zinc or zinc alloy coating to steel or iron which acts as a sacrificial anode to protect the underlying steel or iron. These coatings are mainly used in the automotive and construction industry where corrosive environments will be encountered. There has been a drive to improve the performance of galvanised coatings through alloy additions, initially Al (5 – 55 wt%) and more recently through the development of Zn - Al - Mg coatings. Here, Al and Mg are added as minority additions (typically 1 - 3 wt %) to improve corrosion resistance allowing thinner coatings to be used thus saving material, weight and cost. The assessment of the corrosion performance of such coatings is often evaluated through standardised tests. An industry standard test known as Prohesion or ASTM G85 Annex A5 is carried out on metallic coatings as it is thought to better represent long-term natural exposure than a regular salt spray test. The Prohesion test is a cyclic accelerated corrosion test using an electrolyte of 0.4% Ammonia sulphate and 0.05% sodium chloride (NaCl).This investigation aims to determine the effects on the corrosion performance of zinc-aluminium alloys and zinc-aluminium-magnesium alloys of varying compositions immersed in Prohesion solution. Previous work on this topic suggests that magnesium containing alloys were particularly susceptible to accelerated corrosion in Prohesion solution. Here, several zinc based alloys were immersed in Prohesion solution as well as a control 0.45% sodium chloride solution and subjected to electrochemical testing. The electrochemical techniques used to test said substrates are linear polarisation resistance (LPR), scanning vibrating electrode technique (SVET) and time-lapse optical microscopy (TLM) all for 24 hours. The alloys that underwent testing are shown in Table 1. Table 1: Table showing the composition of substrates used.Sample number Composition 1 Zn-<0.2wt%Al 2 Zn-5wt%Al 3 Zn-55wt%Al 4 Zn-1.2wt%Al-Zn1.2wt%Mg 5 Zn-3.5wt%Al-3wt%Mg 6 Zn-6wt%Al-3wt%Mg The results from the TLM showed differences in the corrosion mechanism that is dependent on the alloy composition and electrolyte. Generally, all substrates immersed in the control 0.45% NaCl showed localised corrosion with distinct anodes developing surrounded by a ring of corrosion product and white rust is observed on the surface of the substrate. The initial site of anodic attack in the microstructure was dependent on the alloy composition. However, when immersed in the Prohesion solution significant differences were observed dependent on the alloy composition. For Zn-Al-Mg coatings rapid attack of zinc-magnesium phases was observed especially in the eutectic regions followed by aggressive attack of the entire exposed surface of the alloy within 6 hours. Additionally, no corrosion product rings formed. For Zn-Al alloy coatings, the zinc phases were preferentially attacked with the aluminium containing phases appearing to be resistant to corrosion during the duration of the tests. No white rust was seen on the surface of the substrates and instead a dark surface/corrosion product film was observed. The corrosion rate from the LPR data measured at hourly intervals over 24 hours increases when substrates are immersed in Prohesion solution compared to NaCl, with the most noticeable increase seen when there are zinc-magnesium phases present within the alloy. The largest increase in corrosion rate mm per year (mmpy) was seen in sample 5 with it increasing from 0.15 mmpy after 24 hours in the control solution to 0.55 mmpy in the Prohesion solution after 24 hours. The same is observed with the SVET results showing that the ammonium ions are having a significant damaging effect on the Zn-Al-Mg metallic coatings. The proposed corrosion mechanism for Zn-Al-Mg alloy coatings in Prohesion solution is preferential dissolution of MgZn2 in eutectic phases due to reactivity of Mg producing Mg(OH)2 which is a highly basic hydroxide. Due to the basic nature of Mg(OH)2, Ammonium (NH4 +) cations react with Mg(OH)2 producing Mg2+ and Ammonia (NH3).Mg(OH)2+2NH4 +=Mg2++2NH3+2H2OZn(OH)2 does not undergo this reaction to the same extent as it hydrolyses in water (producing H+) therefore is not basic enough to support much NH3 production. Neutral NH3 reacts with metallic Zn or Zn2+ compounds to produce highly soluble zinc (II) tetra-ammine complex cations. Therefore, the protective Zn and Mg compounds forming at the metal surface will dissolve and the surface will become activated. This is demonstrated by the lack of white rust shown from samples immersed in the Prohesion solution. Al phases are resistant to NH3 hence the better performance of Zn-Al coatings and the preferential attack of the Zn in the Zn-Al timelapse microscopy.

ОПРЕДЕЛЕНИЕ ТРИБОЛОГИЧЕСКИХ ХАРАКТЕРИСТИК СПЛАВА АЛЮМИНИЙ-КРЕМНИЙ В ЗАВИСИМОСТИ ОТ СОСТАВА ДОБАВОК ДЛЯ ПОРШНЯ ДИЗЕЛЯ ТЕПЛОВОЗА

The study objective is to define the influence of various modifiers on the tribotechnical properties of an aluminum and silicon alloy. Determination of the most optimal additives in alloys that would reduce the friction factor and increase the unit load at which friction pairs set in comparison with the starting material, as well as determination of their wear resistance.&#x0D; Research methods are tests conducted for friction and wear of samples based on aluminum and silicon according to the following: plane (test sample) – the sleeve end (steel 40X), as well as conducting tests with the supply of free abrasive into the friction zone according to the following: flat sample - forming surface of a rubber disc.&#x0D; Research results and novelty: the influence of modifiers in the aluminum and silicon alloy composition on wear resistance and friction ratio at different loads and sliding speeds in a friction pair with steel are established.&#x0D; Conclusions: the regularities of changes in the friction ratio from pressure and speed, the load of seizure from the sliding speed are obtained. The wear resistance of samples with various inclusions is higher compared to the base material.