Fine Intermetallic Compounds Research Articles

Buffered Oxide Etch: A Safer, More Effective Etchant for Additively Manufactured Ti-Alloys

Kroll’s reagent is effective for the metallographic etching of traditional Ti-alloys but struggles with the intricate, refined microstructures of newer Ti-alloy compositions like Ti-Cu and Ti-Mo alloys, which are created through additive manufacturing. The presence of fine intermetallic compounds in these alloys results in limited contrast between grains and phases when using Kroll’s reagent, highlighting the need for an alternative etchant. This study systematically investigates the use of buffered oxide etch, a common etchant for micro-electronics, on a range of additively manufactured Ti-alloys. The results show that buffered oxide etch provides superior etching outcomes compared to Kroll’s reagent and ammonium bifluoride, with a clear colour contrast between grains and fine phases. Furthermore, ammonium bifluoride with an F− ion concentration similar to 40% buffered oxide etch (5.60 mmol/ml) is found to reveal microstructural details effectively. These findings suggest that the buffered oxide etch is a reliable tint etchant for additively manufactured Ti-alloys, and could potentially be used to etch other additively manufactured alloy systems for metallographic studies. Both these etchants supply F− ions without the low pH, significantly improving safety by removing the need for HF in the etching process.

The Preparation and Properties of Ni2Al3 Intermetallic Compound Coating

In this work, a Ni2Al3 intermetallic compound coating was prepared on 45 # steel by combining methods of low-pressure cold spray and heat treatment. Firstly, powders mixed with Ni powders, Al powders, and Al2O3 powders as a mass ratio of 20:6:4 were sprayed on surface of 45 # steel by low-pressure cold spraying technology to prepare a Ni-Al pre-coating. Subsequently, the pre-coating was annealed at 570 °C in an argon atmosphere for 12 h to obtain the Ni2Al3 intermetallic compound coating. The composite coating was characterized using TEM, SEM, and XRD. High temperature oxidation performance of the composite coating was analyzed by isothermal oxidation tests conducted at 600 °C in air atmosphere for 96 h. The results show that the composite coating is composed of Ni2Al3 phase. Under a high-temperature oxidation environment, a protective oxide film composed by Al2O3 and NiO was formed on the coating surface, which resulting in a superior high-temperature oxidation resistance compared to 15CrMo heat-resistant steel. The mechanism of the Ni2Al3 coating resistance to high-temperature oxidation is that an oxide film mainly composed of Al2O3 and NiO formed on the surface during the high-temperature oxidation process; this oxide film can effectively resist oxidation and protect the substrate material from oxidation at a high temperature of 600 °C.

Evaluation of the microstructure, thermal, and mechanical characteristics of Sn-9Zn reinforced with Ni and ZrO2 nanoparticles via vacuum melting process

The impact of minor additions of nickel and ZrO2 nanoparticles to eutectic Sn-9wt%Zn (SZ) prepared by vacuum melting technique was investigated. The morphologies and microstructures were carried out using an optical microscope (OM) and field emission scanning electron microscope technique (FESEM) escorted by energy dispersive x-ray spectrometry (EDX). The phase structure of the specimens was confirmed by an x-ray diffractometer (XRD). The results obtained demonstrate that small Ni addition causes a major grain refinement of β-Sn, due to the formation of the fine intermetallic compounds Ni5Zn21 and Sn3Ni4Zn3 phases and refines the formation of α- Zn lamellar phase. The melting temperature of the recently discovered solder alloys was lower than that of the eutectic Sn-Zn solders (∆Tm ∼ 28 °C) as a result of the preparation technique and the incorporation of Ni and ZrO2 nanoparticles. The tensile test showed enhanced the mechanical properties of SZ solder as a result of the addition of third elements. The experimental results showed that of all the alloys under investigation, the SZN903 alloy had the greatest UTS and YS values. The enhanced strength of the SZ-ZrO2 alloy defended the results of σ UTS and increased the stress exponent parameters, n, by ∼20%. All solders had an activation energy Q that measured between ∼35.62 kJ mol−1 to ∼58.12 kJ mol−1 which comparable to the pipe-diffusion mechanism.

Improvement of Microstructure and Sliding Wear Property of Cold-Sprayed FeAl Intermetallic Compound Coating by Annealing Treatment

Nanograin Fe(Al) solid solution alloy coating was firstly produced through cold-spraying technology using mechanically alloyed powder. Then, the above-mentioned coating was annealed at different temperatures to explore its influence on the phase constitution, microstructure, microhardness and dry sliding wear property of the coatings. Results exhibited that an FeAl phase appeared in the coatings after 500 °C treatment and remained stable with increasing annealing temperature. The annealing temperature had a considerable effect on the microstructure, microhardness and wear behavior of the FeAl coating. The existing laminated structure in the as-sprayed coating gradually faded away with increasing temperature and finally obtained a dense coating microstructure with no particle interface when annealed above 950 °C. Nanograin began to evidently grow at temperatures over 800 °C. The microhardness of the FeAl coating stayed at 400 Hv0.1 at temperatures below 800 °C, then it quickly dropped to 300 Hv0.1 at 950 °C and remained nearly unchangeable up to 1100 °C. The dry sliding wear mechanism of the FeAl coating annealed at low temperatures below 700 °C was mainly delamination of the oxide layer and showed a high wear rate within the order of magnitude range of 10−4, whereas FeAl coatings annealed at high temperatures above 950 °C were worn by microploughing and little oxidation and exhibited very low wear rates within the order of magnitude range of 10−6.

Grain refinement of primary Cu6Sn5 in the Sn-3wt%Ag-5wt%Cu alloy by Ge

Fine grain structure is generally favoured in the alloy system. Here, we demonstrate that the fine intermetallic compounds (IMCs) in Sn-3wt%Ag-5wt%Cu (SAC35) alloy by coupling with different amount of Ge (0–0.15wt%). The effect of Ge addition on the microstructure, elemental distribution, thermal properties, solidification, and corresponding grain refinement mechanisms were studied. The results showed that Cu6Sn5 was explicitly refined in Ge added SAC35 alloys, with a maximum 59% reduction in the size of Cu6Sn5 found in the as-cast bulk SAC35-0.1wt%Ge alloy. Also, the presence of Ge reduced the thickness and grain size at the interfacial IMC layer by 21% and 22%, respectively. Synchrotron micro-XRF results revealed that the Ge preferentially exist in matrix phase. The cooling curve analyses revealed that the solidification time of Ge-coupled is shorter than that of the SAC35 alloy. The undercooling values was found to have decreased with increased Ge addition. The growth restriction factor, Q, was calculated with the aid of Thermo-Calc software, and it was found to have increased in tandem with increasing Ge amounts. The findings suggest the suitability of Ge as a grain refiner for SAC35.

The corrosion behavior of HVOF TiAlNb coating in molten Zn-0.2 wt.% Al

Abstract In order to understand the corrosion behavior of high-velocity oxygen-fuel (HVOF) TiAlNb coatings in molten Zn-0.2 wt.% Al, the different kinds of TiAlNb coating were deposited on 316L stainless steel substrate and the corrosion tests in molten zinc were carried out. The coating morphologies, phase composition, and characteristics of HVOF TiAlNb coatings at different stages of immersion time were studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectrometry (EDX). The results indicated that the HVOF sprayed TiAlNb intermetallic compound coatings have excellent corrosion resistance to molten zinc. The corrosion type of the HVOF TiAlNb coatings in molten Zn-0.2 wt.% Al is pitting corrosion and crack corrosion. In the whole corrosion stage of molten Zn-0.2 wt.% Al, the corrosion time has no effect on the phase compositions of the HVOF TiAlNb coatings.

High entropy intermetallic coatings fabricated by detonation spraying

(Co1/3Fe1/3Cu1/6Ni1/15Mn1/10)Al and (Cu1/4Fe1/4Ni1/4Ti1/4)3Al high entropy intermetallic compound (HEIC) coatings were deposited on low alloy steel substrate by detonation spraying (DS) using pre-alloyed powders. The (Co1/3Fe1/3Cu1/6Ni1/15Mn1/10)Al and (Cu1/4Fe1/4Ni1/4Ti1/4)3Al HEIC powders fabricated by induction melting followed by ball milling had a single B2-ordered and a double B2 + FCC phase structures, respectively, which exhibited excellent stability during DS. The coatings exhibited sound bonding with substrate, and consisted of lamellar microstructure with low porosities. DS is anticipated to be a high throughput technique to fabricate HEIC coatings with dense microstructure for use in different industries.

Preparation of iridium‑hafnium intermetallic compound coatings in molten salts

A uniform and continuous iridium‑hafnium diffusion coating was fabricated using the metalliding process in a molten salt of LiF-HfF4 at relatively low temperatures to improve the oxidation resistance of pure iridium under extreme operating conditions. The phase composition and morphology of the diffusion coatings prepared at different temperatures from 950 to 1200 °C were determined by X-ray diffraction and scanning electron microscopy coupled with energy dispersive X-ray microanalysis, respectively. The results show that the diffusion coating consists of HfIr3, HfIr and Hf2Ir intermetallic compounds. With an increase in temperature, the thickness of the coating increased significantly. This shows that metalliding is a promising method for the preparation of uniform iridium‑hafnium diffusion coatings.

Heat Treatment-Induced Microstructure and Property Evolution of Mg/Al Intermetallic Compound Coatings Prepared by Al Electrodeposition on Mg Alloy from Molten Salt Electrolytes.

A method of forming an Mg/Al intermetallic compound coating enriched with Mg17Al12 and Mg2Al3 was developed by heat treatment of electrodeposition Al coatings on Mg alloy at 350 °C. The composition of the Mg/Al intermetallic compounds could be tuned by changing the thickness of the Zn immersion layer. The morphology and composition of the Mg/Al intermetallic compound coatings were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron backscattered diffraction (EBSD). Nanomechanical properties were investigated via nano-hardness (nHV) and the elastic modulus (EIT), and the corrosion behavior was studied through hydrogen evolution and potentiodynamic (PD) polarization. The compact and uniform Al coating was electrodeposited on the Zn-immersed AZ91D substrate. After heat treatment, Mg2Al3 and Mg17Al12 phases formed, and as the thickness of the Zn layer increased from 0.2 to 1.8 μm, the ratio of Mg2Al3 and Mg17Al12 varied from 1:1 to 4:1. The nano-hardness increased to 2.4 ± 0.5 GPa and further improved to 3.5 ± 0.1 GPa. The Mg/Al intermetallic compound coating exhibited excellent corrosion resistance and had a prominent effect on the protection of the Mg alloy matrix. The control over the ratio of intermetallic compounds by varying the thickness of the Zn immersion layer can be an effective approach to achieve the optimal comprehensive performance. As the Zn immersion time was 4 min, the obtained intermetallic compounds had relatively excellent comprehensive properties.

Optimal Hot-Dipped Tinning Process Routine for the Fabrication of Solderable Sn Coatings on Circuit Lead Frames.

Previous studies merely focus on the hot dipping properties of lead frame materials used in electronic industry. Yet, the environmentally friendly and cost-efficient traits of hot-dipped tinning process make it a possible promising surface modification technique compared with electroplating. As a result, the optimal hot-dipped tinning process routine is proposed in this paper. The hot-dipped tinning process of four different types of copper foils (C11000, C19400, C19210, and C70250), pretreatment parameters, mechanical properties of Cu substrates, thickness of IMC (intermetallic compound) layers and coatings, and microstructure of coatings were investigated to determine the copper substrate suitable for hot-dipped tinning and the optimized tinning procedures. The results indicate that a proper increase in alloying elements (e.g., Cu-Fe-P series alloys) towards Cu substrate leads to a decrease in hot dipping performance. The proper process routine is determined as alkaline cleaning→water scrubbing→accelerant solvent dipping→drying→hot-dipped tinning→cooling. The appropriate dipping temperature range is 260 to 280 °C, which assists to maintain acceptable micro hardness (i.e., maintaining at least 95% of the original hardness). The optimal dipping time should be set as 6–10 s. The proposed hot-dipped tinning process routine may present a guideline for the fabrication of tin coating in electronic industry.

Influence of Ni and Cr on the high-temperature wear resistance of FeNiCrAl coatings

Abstract To reduce the brittleness of Fe-Al intermetallic compound coatings, FeNiCrAl powder wire for high-speed electric arc spraying is developed by integrating Ni and Cr into an Fe-Al intermetallic compound. The corresponding FeNiCrAl coating is prepared via high-speed electric arc spraying technology. A 3Cr13 coating is selected as the material for comparison, and the friction and wear properties of the two coatings are investigated from 200 °C to 800 °C. The friction coefficient variations and friction surface topography patterns of the two coatings are analyzed via X-ray diffractometry (XRD), hardness testing, and scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS). The phase compositions of the materials on the wear surfaces are analyzed via X-ray photoelectron energy spectrometry (XPS). The results show that after the friction coefficient of the FeNiCrAl coating reaches its peak value at 400 °C, it declines with increasing temperature, and its wear volume is less than that of the 3Cr13 coating. An XPS-based wear surface composition analysis and SEM wear scar topography results show that the FeNiCrAl coating produces not only Fe, Ni and Cr oxides but also Ni-Al intermetallic compounds during high-temperature friction. After the friction coefficient of the FeNiCrAl coating reaches its peak at 800 °C, more Al2O3 is formed around the Fe3Al, and these compounds aggregate to form a protective film that effectively prevents further intrusion of O ions. A dense oxide layer covers the wear surface, and the formation of hard-phase chemical compounds improves the wear resistance and bearing capability of the coating.

Corrosion characteristics of Fe3Si intermetallic coatings prepared by molten salt infiltration in sulfuric acid solution

Alloyed Fe3Si intermetallic compound coatings were prepared through non-electrolysis high-temperature infiltration in molten salt on the surface of AISI420 and AISI304 stainless steel containing Cr and Cr, Ni elements, compared with Fe3Si coating on A3 carbon steel surface. The microstructure of infiltration coatings was examined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy. The electrochemical corrosion properties and behavior of Fe3Si coatings in H2SO4 solution were evaluated via electrochemical techniques and static immersion tests. The results revealed that the permeation coatings prepared on the stainless steel surface are composed of a Cr- and Cr-, Ni-alloyed Fe3Si intermetallic-compound layer and a diffusion layer. Owing to the presence of alloying elements Cr and Ni from the substrate, the permeation coatings were relatively thick, dense, and contained only a few defects. The Cr-, Ni-alloyed Fe3Si coating prepared on AISI304 surface was the most compact, contained fewer defects, and was thicker than the coating prepared on AISI420. The Fe3Si infiltration coatings exhibited significant passivation characteristics in 10 vol% H2SO4 aqueous solution. Alloyed Fe3Si coatings of AISI420 and AISI304 exhibit better corrosion resistance in 10 vol% and 20 vol% H2SO4 than the Fe3Si coating of carbon steel. Therefore, these coatings can protect both types of stainless steel from surface corrosion. The best corrosion resistance was realized for the alloyed Fe3Si coating on AISI304 surface. The corrosion resistance and protection performance of Fe3Si intermetallic-compound coatings in H2SO4 solution are directly correlated with the thickness, compactness, defect characteristics, and passivation properties of the infiltration coatings. However, alloying elements from the alloy steel substrates had a significant effect on these four factors, during the infiltration process in the molten salt.

Effect of aluminium on microstructure, mechanical property and texture evolution of dual phase Mg-8Li alloy in different processing conditions

The present study investigates the possibility of enhancing the strength with ductility of dual-phase magnesium (Mg)-8 lithium (Li) alloy by the combination of alloying addition aluminium (Al) and suitable thermo-mechanical processing. Microstructural evolution, phase analysis and texture studies were performed for Mg-8Li-xAl (x=0, 2,4 and 6) alloys with the help of scanning electron microscopy (SEM) and X-ray diffraction (XRD). It is understood from the texture studies that the addition of Al to the Mg-8Li alloys activates the non-basal slip at room temperature. In turn, it facilitates the recovery process, hence a substantial improvement in plastic deformation after annealing of the alloys is observed. This is attributed to non-basal slip activity at room temperature. The presence of fine intermetallic compounds in the annealed Mg-8Li-xAl (x=4 and 6) alloys leads to the higher ultimate strength (193±7MPa and 267±9MPa) and ductility (20% and 17%), respectively.

Evaluation of Tensile Strength in Friction Stir Welded Aluminum alloy 6101-T6 and commercially pure Copper joints

In the present investigation, an experimental study has been conducted to optimize the critical process parameters such as tool geometry, shoulder diameter to pin diameter ratio, welding speed, rotational speed and pin offset on the tensile behavior of friction stir welded aluminum alloy 6101-T6 and commercially used pure copper using Taguchi’s L 16 design of experiment and all the parameters were varied across two levels. Tensile tests were performed to evaluate weld properties and results were validated using energy dispersive tests. Thorough mixing of dissimilar materials in nugget zone was observed corresponding to best experimental conditions resulting in the maximum tensile strength of 181 MPa. Fine copper particles were distributed over aluminum base material resulting in the formation of fine intermetallic compounds in nugget zone that increased tensile strength of joint.

激光熔化沉积NiTi基金属间化合物涂层的微结构与性能

激光熔化沉积NiTi基金属间化合物涂层的微结构与性能

Microstructure and mechanical properties of nickel particle reinforced magnesium composite: impact of reinforcement introduction method

AbstractIn this study, magnesium was reinforced with micrometer size fine pure nickel particles using the ingot and powder metallurgy processes. The ingot metallurgy process induced a matrix–reinforcement reaction in the magnesium matrix, produced an enormous number of fine intermetallic compound particles and reduced the pure nickel particle size. The powder metallurgy process preserved the incorporated nickel particle intact. The ingot metallurgy made a remarkable improvement in the strength of the reinforced magnesium matrix with marginal strain hardening. The powder metallurgy process did not affect the yield strength of the reinforced magnesium matrix while inducing large strain hardening during plastic deformation. The fracture mode was similar for the ingot and powder metallurgy processed reinforced magnesium samples.

Tribological properties of laser cladding NiAl intermetallic compound coatings at elevated temperatures

Tribological properties, phase compositions and wear mechanisms of laser cladding NiAl coating were investigated from room temperature to 1000°C under air atmosphere environment. The results showed that a glaze layer composed of NiO, Ni2O3, Al2O3 and NiAl2O4 phases as well as Ni3Al phase were formed on worn surface under high temperature, which act as a solid lubricant and anti-wear material improving the tribological properties of NiAl coating at elevated temperatures. The wear mechanism is dominated by abrasive wear below 500°C, and transforms to plastic deformation and adhesive wear at 500°C up to 700°C and oxidation wear at 900°C and above, owing to formation of new oxide phase during tribochemical reaction.

Effect of the Mean Size of Fine Intermetallic Compounds on the Strength Property of Sintered Magnesium Alloy by Gas Atomization

Effect of the Mean Size of Fine Intermetallic Compounds on the Strength Property of Sintered Magnesium Alloy by Gas Atomization

Structural size effects of intermetallic compounds on the mechanical properties of Mo-Si-B alloy: An experimental investigation

In general, size, shape and dispersion of phases in alloys significantly affect mechanical properties. In this study, the mechanical properties of Mo-Si-B alloys were experimentally investigated with regards to the refinement of intermetallic compound. To confirm the size effect of the intermetallic compound phases on mechanical properties, two differently sized intermetallic compound powders consisting Mo5SiB2 and Mo3Si were fabricated by mechano-chemical process and high-energy ball milling. A modified powder metallurgy method was used with core-shell intermetallic powders where the intermetallic compound particles were the core and nano-sized Mo particles which formed by the hydrogen reduction of Mo oxide were the shells, leading to the microstructures with uniformly distributed intermetallic compound phases within a continuous α-Mo matrix phase. Vickers hardness and fracture toughness were measured to examine the mechanical properties of sintered bodies. Vickers hardness was 472 Hv for the fine intermetallic compound powder and 415 Hv for the coarse intermetallic compound powder. The fracture toughness was 12.4 MPa·√m for the fine IMC powders and 13.5 MPa·√m for the coarse intermetallic compound powder.

Effects of Graphite Additions and Heat Treatment on the Microstructure, Mechanical and Tribological Properties of 13% Chromium White Iron

A 13% chromium white iron was produced using a stir cast process. Samples of the produced white iron were austenised at 1450°C and then quenched in water to the room temperature. The characterisation tools such as X-ray diffractometer, scanning electron microscope, Brinell hardness tester and pin on disc machine were employed in the studies of the phase orientation and morphology, hardness value measurement and investigation of wear behaviour. The results revealed that water quenching the 13% chromium white iron led to the precipitation of fine iron chromides and cementite in the matrix of martensite. Moreover, there is an about 22% to 45% increase in hardness values of the as-cast 13% chromium white iron as the %composition of graphite additions increased from 1.36 to 3.04. However, the impact energy values are sacrificed. The increase in hardness values is attributable to hard intermetallic compounds such as iron chromides and cementite phases in the iron matrix. Also, there is an about 32% - 42% increase in hardness values of the heat treated samples of 13% chromium white iron when compared with those of the as-cast. The increased hardness values are attributable to even distribution of the fine intermetallic compounds in the fine grains of martensitic matrix. The wear rate increased as the sliding moments per unit time increased due to increasing work done by the friction to oppose the rotation of the pin on disc. The water quenched 13% chromium white iron samples have greater wear resistances than the as-cast samples due to their greater hardness values than those of the as-cast samples. The effect of speed increase on decreasing wear resistances is more pronounced on the heat treated samples than on the as-cast samples. Hence, the water quenched 13% chromium white iron is an excellent material in application requiring high wear resistance and low impact energy especially in grinding mill liner plate, bottom or casing used in the concrete pipe production, roller for crushing and pulverising mills.