Intermetallic Compound Particles Research Articles

Mechanical Bonding Properties of Solderable Anisotropic Polymer Composite containing Low-Melting-Point and High-Melting-Point Solder Fillers

In this papers, to enhance the mechanical bonding properties of solderable anisotropic polymer composites (SAPCs) containing low-melting-point solder filler only, a new low-melting-point solder and high-melting-point solder mixed filler filled SAPCs (LH-SAPCs) was proposed, and the influence of the high-melting-point solder filler on the conduction path formation and mechanical bonding properties of the LH-SAPC were investigated. Two types of LH-SAPC were synthesized by adding high-melting-point solder within the low-melting-point solder/high-melting-point solder mixed filler at mixing ratios of 0 and 50 vol% (the volume fraction of low-melting-point solder/high-melting-point solder mixed filler in the polymer composite was 20%), and a bonding test was conducted using QFP. The results exhibited that the LH-SAPC containing high-melting-point solder formed a wide and stable conduction path due to the proper selective conduction path formation behavior by the interaction between molten low-melting-point solder and solid-state high-melting-point solder fillers within the polymer composite with low viscosity condition. Furthermore, the mechanical bonding properties of the LH-SAPC joints containing high-melting-point solder were enhanced compared to that of LH-SAPC containing low-melting-point solder only owing to the precipitation hardening and dispersion strengthening effects due to the increase of fine Bi-rich, Cu<sub>6</sub>Sn<sub>5</sub>, and Ag<sub>3</sub>Sn intermetallic compound particles inside the conduction path.

Structural, thermal and mechanical properties of rapidly solidified Bi-0.5Ag lead-free solder reinforced Tb rare-earth element for high performance applications

Purpose The purpose of the present work is to study the impacts of rapid cooling and Tb rare-earth additions on the structural, thermal and mechanical behavior of Bi–0.5Ag lead-free solder for high-temperature applications. Design/methodology/approach Effect of rapid solidification processing on structural, thermal and mechanical properties of Bi-Ag lead-free solder reinforced Tb rare-earth element. Findings The obtained results indicated that the microstructure consists of rhombohedral Bi-rich phase and Ag99.5Bi0.5 intermetallic compound (IMC). The addition of Tb could effectively reduce the onset and melting point. The elastic modulus of Tb-containing solders was enhanced to about 90% at 0.5 Tb. The higher elastic modulus may be attributed to solid solution strengthening effect, solubility extension, microstructure refinement and precipitation hardening of uniform distribution Ag99.5Bi0.5 IMC particles which can reasonably modify the microstructure, as well as inhibit the segregation and hinder the motion of dislocations. Originality/value It is recommended that the lead-free Bi-0.5Ag-0.5Tb solder be a candidate instead of common solder alloy (Sn-37Pb) for high temperature and high performance applications.

Modes of wear of babbitt-based composite materials produced by hot pressing

The effect of additives of Ti2NbAl intermetallic compound on the friction of B83 babbitt samples obtained by hot pressing was studied using optical, electron microscopy and EDS analysis. The structure, friction surface and wear products were studied. Tribological tests were carried out on a universal test system under conditions of dry sliding friction according to the scheme of axial loading: a steel bush against a disk of the material under study. The temperature values near the friction zone were recorded. The limits of application of the material depend on the mode and mechanism of wear occurring in the tribocontact. Changes in the mode and mechanism of wear were assessed by differences in the behavior of the friction coefficient, temperature, difference in the state of friction surfaces, wear intensity and wear products. The results obtained indicate the prospects of using the method of hot pressing of powder from the B83 alloy and discrete particles of the high-strength Ti2NbAl intermetallic phase to get composite materials with improved tribological properties compared to a babbitt alloy. The introduction of reinforcing high-modulus particles of intermetallic compounds changed the structure of the material and affected the friction processes in babbitt, pushing aside the onset of change in the mode of wear towards more severe friction conditions. A significant decrease in the wear intensity of babbitt-based composite materials compared to the original alloy makes it possible to predict an increase in the service life of tribo-units. The data obtained enable us to determine and recommend modes that improve the performance of tribo-nodes in the manufacture of both volumetric inserts and plain bearings made of B83 alloy and, moreover, to create new functionally organized layered compositions with enhanced tribotechnical properties with a base of structural steels and working surface layers not only using B83 babbitt, but also of composite materials based on B83 babbitt.

Revealing hot tear formation dynamics in Al–Cu alloys with X-ray radiography

Hot tears can arise during the late part of alloy solidification because of the shrinkage of isolated liquid as it turns to solid and may have a catastrophic effect on cast tensile properties. Although there are correlations to suggest alloy hot tear sensitivity to casting conditions, they do not capture the influence of microstructure on tearing, such as second-phase particles or intermetallic compounds (IMCs) commonly present in engineering alloys. We use in situ X-ray radiography to quantify the formation and growth behaviour of hot tears in Al-5Cu and Al-5Cu-1Fe alloys during solidification. An automated hot tear detection, tracking and merging algorithm is developed and applied to reveal the role of Fe-rich IMC particles, typical of recycled alloys, on hot tear behaviour. These defects are termed hot tears here on the basis of their complex, extended inter-connected morphology, distinct from more rounded shrinkage porosity. We also visualise and quantify the velocity of interdendritic flow driven by solidification shrinkage, and estimate the pressure changes due to shrinkage. Hot tearing starts at lower solid fraction when IMCs are present due to reduced interdendritic flow, and hot tear formation is more spatially homogeneous, less clustered and more numerous. We show that the largest, most damaging hot tears form from many merging events, that is enhanced by the presence of IMCs.

Refractory high-entropy aluminized coating with excellent oxidation resistance and lubricating property prepared by pack cementation method

Refractory high-entropy alloys (RHEAs) exhibit superior mechanical properties at high temperatures compared to that of conventional high-temperature alloys. However, some refractory metallic elements are highly susceptible to oxygen absorption at room temperature and the resulting oxide films are not protective, resulting in catastrophic oxidation before they can exhibit excellent mechanical properties. Therefore, it is essential for them to improve the high-temperature oxidation properties of RHEAs. The pack cementation method can be used to prepare the aluminized coatings on the surface of RHEAs to improve their high-temperature oxidation resistance. In the present work, the aluminized high-entropy coatings were prepared on the surface of as-cast Ta25Nb25W25V25 RHEAs. The diffusion activation energy required for aluminization was experimentally calculated to be 137.667 kJ/mol, thus the growth kinetics of the coating was constructed. Aluminized coatings with the thickness of ∼75 μm and Vickers hardness of ∼680 HV0.01 obtained by holding at 1100 °C for 9 h were selected for the study. The oxidation activation energy of the aluminized coating at 800–1000 °C was 96.981 kJ/mol, while that of as-cast RHEAs was only 48.816 kJ/mol, so the oxidation resistance of the specimen was greatly improved. At 20–600 °C, the aluminized coatings also exhibited excellent wear resistance and lubrication properties. In particular, the average coefficients of friction were reduced by 0.13–0.24 compared to that of as-cast RHEAs, which can be attributed to the AlW intermetallic compound particles formed within the aluminized coating acting as self-lubricating particles.

Effects of Material Structure on Stress Relaxation Characteristics of Rapidly Solidified Al-Fe Alloy.

An Al-Fe alloy which was produced by hot extrusion of rapidly solidified powder is a possible solution to substitute copper-based electrical conductor material due to its high strength and high electrical conductivity. However, the stress relaxation characteristic-an essential parameter as a conductor material-and the effect of the material structure have not been reported, which was the aim of the present paper. An Al-5%Fe alloy was selected as the test material. The material structures were controlled by hot extrusion practice, annealing, and cold rolling. The Al-Fe intermetallic compound particles controlled the residual stress after the stress relaxation test via the Orowan mechanism. Decreasing the mean inter-particle distance reduces the electrical conductivity. The increase in the number of dislocations by the cold rolling increased strength at room temperature without changing electrical conductivity; however, it did not have a positive effect on the stress relaxation characteristics. The stress relaxation characteristics and the electrical conductivity of the Al-Fe alloy were superior to conventional C52100 H04 phosphor bronze when compared with the case of the same mass.

Steam reforming of methanol on highly stable MgO–Al2O3 supported Ni–In intermetallic compounds

MgO–Al2O3 supported metallic Ni and Ni–In intermetallic compounds (IMCs) with different Ni/In atomic ratios were prepared by co-precipitation, and their performance for methanol steam reforming (MSR) was tested on an atmospheric fixed-bed quartz reactor. It has been found that the supported Ni–In IMCs give remarkably higher selectivity to H2 than metallic Ni. On one hand, methanation is significantly suppressed on Ni–In IMCs. On the other hand, different from metallic Ni where methanol decomposes followed by water gas shift to generate H2, Ni–In IMCs promote the direct conversion of CH3OH and water to produce CO2 and H2. Among the as-prepared catalysts, the supported Ni2In IMC has the best performance. The methanol conversion and the selectivity of H2 reach about 85% and 97% at 300 °C, respectively, without obvious change during 80 h time on stream. The good stability of supported Ni2In IMC is attributed to its high resistance to Ni2In IMC particles sistering and carbon deposition.

Grain Refinement of Cast Aluminum by Heterogeneous Nucleation Site Particles with High Lattice Matching

A number of studies have been carried out to identify the mechanism of grain refinement in cast aluminum alloys by addition of grain refiners containing potent heterogeneous nucleation site particles. Although some mechanisms and theories have been proposed, in this review, the role of heterogeneous nucleation site particles on grain refining performance will be focused. The content of this article is as follows. First, the morphology of Al3Ti particles in the Al–Ti refiners is presented, since the grain refining performance of the Al–Ti refiners is affected by the morphology of the Al3Ti particles. Evaluation methods of lattice matching between heterogeneous nucleation site and crystallized phase are, then, discussed. Since we conclude that M value is potentially applicable to predict the effective heterogeneous nucleation site, M value at elevated temperatures is described. Next, fragmentation behavior of Al3Ti particles caused by deformation of the refiners is presented, because the number density of the Al3Ti heterogeneous nucleation site particles is increased by the fragmentation of Al3Ti particles. At the same time, the morphology of the Al3Ti particles, which affects the grain refining performance, can be changed. The concept of grain refiners with high-symmetry L12 modified (Al1−xMex)3Ti intermetallic compound particles, fabrication method and some results on grain refining performance are also given. Finally, application of heterogeneous nucleation for other fields are described.

Effects of Near-amorphous multiphase intermetallic compound particles on the microstructure and mechanical properties of SnBi solders

Effects of Near-amorphous multiphase intermetallic compound particles on the microstructure and mechanical properties of SnBi solders

Compressive properties of AlSi10Mg foams additively manufactured with different foaming agents TiH2 and ZrH2

This study investigates the compressive properties of AlSi10Mg foams additively manufactured with different foaming agents: TiH2 and ZrH2. The results of the compression test confirm that compressive energy is absorbed by the collapse of the porous structure, the pores disappear, and the AlSi10Mg foam becomes densified. The pores inside the AlSi10Mg foam result in a decreased yield strength; however, the Young's modulus is increased owing to the intermetallic compound and residual particles inside the foam. AlSi10Mg foamed with TiH2 (as-foamed (TiH2)) has a low maximum compressive stress, which increases the densification strain but decreases the specific energy absorption. In contrast, AlSi10Mg foamed with ZrH2 (as-foamed (ZrH2)) exhibits the highest specific energy absorption. The high wettability of the Al/Zr system causes the intermetallic compound to be uniformly dispersed. Thus, the product foamed with ZrH2 exhibits higher compressive properties than that foamed with TiH2. This confirms that in fabrication of AlSi10Mg foams, TiH2 and ZrH2 produce different foaming characteristics, compressive properties, and intermetallic compound distributions.

Interfacial microstructure and strength of magnetic pulse welded A5052 aluminum alloy/SPCC steel lap joint

A5052 aluminum alloy and SPCC steel plates were welded using magnetic pulse welding, and interfacial microstructure and strength of the lap joint were examined. The A5052 aluminum alloy and the SPCC steel plates were used for a flyer plate and a parent plate, respectively. Charging energy stored in capacitor and gap between the A5052 aluminum alloy and the SPCC steel plates were changed. Microstructure was examined by using an optical microscope, a scanning electron microscope and a scanning transmission electron microscope. Tensile-shear test was used for evaluating the strength of the joint. The magnetic pulse welding of A5052 aluminum alloy and SPCC steel was achieved at the charging energy above 6.0 kJ and at the gap between the plates above 1.0 mm. The range of charging energy in which the strong welding is accomplished was different at each gap and the range increased with decreasing the gap. The lap joint was not fractured at the welding interface by the tensile-shear test whereas the fracture occurred at a part of the aluminum base metal. The welding interface exhibited characteristic wavy morphology. An intermediate layer was produced along the wavy interface. Scanning transmission electron microscope observation revealed that the intermediate layer is composed of fine Al-Mg grains and dispersed dendritic Al-Fe intermetallic compound particles.

Effects of Au/Ni coating thickness on enhancing the properties of InPb/MoCu solder joints in microwave modules

Deep understanding of and effective improvement in interconnect performance are of great significance for developing miniaturized and high-performance microwave modules. Herein, the effects of Au/Ni coating thickness on the performance of InPb interconnect solder joints were investigated by the high-temperature storage experiment. At normal Au/Ni joints, the AuIn2 intermetallic compound (IMC) particles bordered on each other, attributing to form a “closed zone” where the diffusion rate of In atoms was faster than that of Au atoms and there was a net flux. Here, the vacancies in the “closed zone” were merged in reaction to form Kirkendall voids. However, the “closed zone” inside the thin Au/Ni joints could be greatly reduced, and thus the generation of voids was significantly suppressed. The diffusion coefficient of AuIn2 IMCs was reduced by 22.34% at the thin Au/Ni joints compared with the normal Au/Ni joints. After aging for 168 h, the shear strength of the thin Au/Ni joints was increased by 25.10% compared with the other one. Therefore, the thin Au/Ni coating could enhance the long-term performance of solder joints in microwave modules and meet the development requirements of microwave module miniaturization.

Interfacial Microstructure and Strength of Magnetic Pulse Welded A5052 Aluminum Alloy/SPCC Steel Lap Joint

A5052 aluminum alloy and SPCC steel plates were welded using magnetic pulse welding, and interfacial microstructure and strength of the lap joint were examined. The A5052 aluminum alloy and the SPCC steel plates were used for a flyer plate and a parent plate, respectively. Charging energy stored in capacitor and gap between the A5052 aluminum alloy and the SPCC steel plates were changed. Microstructure was examined by using an optical microscope, a scanning electron microscope and a scanning transmission electron microscope. Tensile-shear test was used for evaluating the strength of the joint. The magnetic pulse welding of A5052 aluminum alloy and SPCC steel was achieved at the charging energy above 6.0 kJ and at the gap between the plates above 1.0 mm. The range of charging energy in which the strong welding is accomplished was different at each gap and the range increased with decreasing the gap. The lap joint was not fractured at the welding interface by the tensile-shear test whereas the fracture occurred at a part of the aluminum base metal. The welding interface exhibited characteristic wavy morphology. An intermediate layer was produced along the wavy interface. Scanning transmission electron microscope observation revealed that the intermediate layer is composed of fine Al–Mg grains and dispersed dendritic Al–Fe intermetallic compound particles.

Структура и микромеханические свойства СВС-композитов с медной матрицей: особенности формирования

Self-propagating high-temperature synthesis (SHS) is one of the promising methods for producing strong and wear-resistant composites. The use of copper as a matrix due to the unique combination of electrical and thermal conductivity is of particular interest. Monolithic SHS composites of the Cu–Ti–C–B and Cu–Ti–C systems are currently little studied. The information on the phase composition of such composites is contradictory, and data on micromechanical properties is practically absent. The paper presents the results of a comparative analysis of the structure and micromechanical properties of composites of the Cu–Ti–C and Cu–Ti–C–B systems. It is found that the matrix of both composites is a copper-based solid solution supersaturated with titanium, in which nanosized Cu4Ti intermetallic compound particles precipitate upon cooling. TiC particles (Cu–Ti–C composite) and TiC and TiB2 particles (Cu–Ti–C–B composite) are the strengthening phases resulting from SHS. In the Cu–Ti–C–B composite, the original particles of unreacted B4C boron carbide were preserved, the microhardness of which was 3680 HV 0.1. The most ductile structural constituent in the Cu–Ti–B system composite is the Cu+Cu4Ti mechanical mixture, due to which further plastic deformation is possible to obtain parts of a given shape. During the study of micromechanical properties, the maximum strength indicators of HIT, HV, We, Re, HIT/E* were recorded in the Cu–Ti–C–B system composite, which allows expecting high wear resistance of products made of it.

A Review on the Friction Stir Brazing for Joining Dissimilar Materials

Friction stir brazing (FSB) is a new technology developed for its ability to join similar and dissimilar metals and alloys resulting in a joint with considerable characteristics through the use of interlayer (braze) material under the action of a pinless rotating tool and other FSB parameters. The frictional heat during FSB is responsible for the melting of the braze material between the two workpieces, while the shoulder action must be satisfactory for the extrusion of the excess braze liquid phase depending on the FSB parameters used. The parameters of FSB also have a considerable impact on the microstructure and mechanical characteristics of friction stir brazed (FSBed) joints. Sound interfacial bonding can be observed in the central zone of FSBed joints, where intermetallic compounds (IMCs) can be formed by direct diffusion among the dissimilar workpieces after extrusion of liquid phase rather than by mechanical mixing or solidification of braze material. Increasing the transverse speed at a constant rotational speed has an influence on the peak temperature, but it remarkably reduces the holding time owing to the increased cooling rate. The use of vibration in the FSB increments the fluidity of the molten braze material among the joining workpieces resulting in a more homogeneous distribution of IMCs particles. In this review article, FSB parameters, bonding mechanisms, as well as the microstructure, and mechanical properties of FSBed joints are reviewed.

Suppression of Hydrogen Embrittlement due to Local Partitioning of Hydrogen to Dispersed Intermetallic Compound Particles in Al–Zn–Mg–Cu Alloys

Recent studies have revealed that hydrogen embrittlement in Al–Zn–Mg alloys appears to be dominated by hydrogen partitioning to MgZn2 precipitates. A method has recently been proposed for reducing the hydrogen concentration at MgZn2 precipitates by adding specific intermetallic compound particles that have high hydrogen trap energy. In the present study, the effectiveness of Al7Cu2Fe particles on suppression of hydrogen embrittlement in Al–Zn–Mg–Cu alloys was evaluated using X-ray microtomography. Quasi-cleavage cracks were found to be initiated in regions where local volume fractions of the Al7Cu2Fe particles were relatively low. Hydrogen partitioning to the MgZn2 precipitate interface was suppressed, even in high hydrogen concentration material, by adding Al7Cu2Fe particles. However, the fractional area of the quasi-cleavage fracture in the material with high hydrogen concentration was higher due to insufficient hydrogen diffusion inside the Al7Cu2Fe particles and at the interface between the aluminum matrix and the particles. It appears that finely distributed small Al7Cu2Fe particles might effectively suppress hydrogen embrittlement.

Interactions of primary intermetallic compound particles and double oxide films in liquid aluminum alloys

One of the main challenges in processing aluminum alloys in the liquid state is the avoidance of the formation of double oxide films and their incorporation into the final parts. Bifilms in liquid alloys can act as heterogeneous nucleation sites for primary intermetallic compounds (IMCs), which phenomenon can be utilized for their aided sedimentation. In this study, TiAlSi IMCs were used for the sedimentation treatment of a liquid Al–Si–Mg–Cu alloy. The interactions between IMCs and bifilms were studied by computed tomography (CT) and scanning electron microscopy (SEM), while the changes in melt quality were assessed by the CT analysis of reduced pressure test (RPT) samples. Additionally, the grain refinement effect of Ti-addition was studied by grain size measurements. It was found that (Al, Si)3Ti particles became attached to bifilms, and their simultaneous sedimentation resulted in lowered porosity. However, the attachment of IMCs to the surface oxide layer caused Ti-macrosegregation in the top region of the melt. The attachment of (Al, Si)3Ti intermetallic particles is caused by the heterogeneous nucleation of IMCs on oxide films and the partial engulfment of oxide film segments during the growth of the (Al, Si)3Ti particles. Investigations of the pore surfaces support the theory of bifilm-initiated pore formation.

Behavior of Al-Zr intermetallic compound particles under high-amplitude ultrasound irradiation into molten aluminum

Recent trends in the aluminum industry toward increasing the recycling rate of aluminum alloys have led to difficulties in controlling the formation of intermetallic compounds (IMCs). The up-to-date investigations have revealed that ultrasonic irradiation is a promising tool to refine and modify the intermetallic compounds formed in the melt before or during casting, and the reported mechanisms include ultrasound-assisted nucleation and fragmentation of compounds. This work presents results concerning the modification effect of ultrasound on model Al3Zr compounds with emphasis on the effect of vibration amplitudes. The results reveal that needle-like Al3Zr compounds can be significantly modified to thicker shape when amplitude increases from 38 µm to 48 µm, and then change to more rounded shape with the further increase of amplitude. Theoretical consideration and numerical simulation show that in addition to the above-mentioned mechanisms, cavitation-induced heat generation and mircrojet-driven mass transfer are also of prime importance in controlling the morphology and growth of IMCs.

Suppressed hydrogen embrittlement of high-strength Al alloys by Mn-rich intermetallic compound particles

The pursuit of strong and ductile Al alloys with superior resistance to hydrogen embrittlement (HE) is practically significant across the aerospace and transportation industries among others. Unfortunately, effective ways to progress on the strength-HE trade-off for Al-alloys remain elusive. A strategy of suppressing HE by introducing intermetallic compound (IMC) particles to achieve hydrogen redistribution in various trapping sites was proposed. Here, we systematically induce the precipitation of a constant volume fraction of intermetallic compound (IMC) particles by adding one of 14 elements in a ternary Al-Zn-Mg high-strength alloy. We show a strong correlation between hydrogen trapping energies of the IMC obtained from ab initio calculations with the resistance to HE. Mn-rich Al11Mn3Zn2 particles exhibit the highest hydrogen trapping energy (0.859 eV/atom), leading to a decrease by approximately 5 orders of magnitude in the hydrogen occupancy in η2 (MgZn2) phase interfaces and grain boundaries, where HE cracks initiate. The Mn-addition did not deteriorate the ductility and most Al11Mn3Zn2 particles remained intact during plastic deformation which was revealed by in-situ 3D X-ray tomography. Hydrogen-induced strain localization at η2 phase interfaces and grain boundaries were inhibited due to strong hydrogen trapping capacity of Al11Mn3Zn2, hence preventing HE cracks initiation. Our approach effectively suppresses hydrogen-induced cracks without sacrificing the ductility, and our strategy can help the design roadmap of HE-tolerant high-strength metallic alloys.

Thermal Stability of L1 2 ‐Modified Al 2.5 Cu 0.5 Ti Particles in Al Matrix

Herein, the thermal stability of two morphologically differently shaped L12-modified Al2.5Cu0.5Ti intermetallic compound particles in the same Al matrix is studied by heating the Al–Al2.5Cu0.5Ti refiner fabricated by spark plasma sintering. Studying the thermal stability of two morphologically differently shaped L12-modified Al2.5Cu0.5Ti intermetallic compound particles in the same Al matrix allows us to control the external experimental factors for both particles at the same time. This gives better results for comparative studies. The result shows that the heat treatment conditions and the different morphology of the L12-modified Al2.5Cu0.5Ti particles can affect the thermal stability of Al2.5Cu0.5Ti particles in the Al matrix. In addition, the effect of heat treatment on the hardness behavior is evaluated with the Vickers microhardness test. The result shows the variation in hardness with increased heating time.