Low Melting Point Metal Research Articles

Study on thermal contact resistance of low melting alloy used as thermal interface material

The development of reliable electronic equipment is a big challenge due to miniaturization and performance characteristics of high speed and high power electronic devices. Thermal control is one of the key roles to meet the above challenge. Thermal Interface Material (TIM) plays a significant role in thermal control. TIM has been extensively used in diverse electronic devices for next generation electronics. To improve or enhance heat transfer performance at the interface region between copper substrates, Low Melting Alloy (LMA) Bi-Sn-Pb is usually used as TIM. In the present work, Thermal contact resistance (TCR) and Temperature variation by TIM is experimentally investigated. In the study, Bi39.4Sn30.8Pb29.8 is used as TIM material. The variation of TCR subjected to heat flow, variation of temperature between the interface and specimen thickness is reported and discussed.

Оцінка чистоти Cd, Zn, Pb шляхом безконтактного вимірювання питомого електроопору за температури рідкого азоту

High-purity fusible metals Cd, Zn, Pb and archaeological archPb are used as component elements in semiconductor and low-background scintillation detectors based on CdTe, CdZnTe, CdWO4 PbWO4 , ZnWO4 required for registering ionizing radiation and searching for particles of dark matter, rare alpha and beta decays. The detection efficiency and the sensitivity of detectors significantly depend on the purity of the constituent elements of detector materials. The dependence of the resistivity of fusible metals Cd, Zn, Pb on the degree of their purity was studied using the non-destructive technique of registering the decaying vortex currents induced in cylindrical samples after dropping the external magnetic field. The aim of the work was to determine the possibility of evaluating the purity of fusible metals using a simple methodology for measuring the characteristic times of decay of vortex currents at 77 K without the use of liquid helium. The computer analysis of the recorded signals presented in the form of decaying curves allowed finding the areas where the signal can be represented as an exponent with a characteristic decay time τ and determining a formula that related τ, specific resistance ρ, and the diameter of cylindrical samples. A comparison of the ρ values of both the initial samples of cadmium, zinc, lead, and archaeological lead, and those samples after various purification procedures, allowed establishing the dependence of the resistivity on the purity of the studied materials at the temperature of liquid nitrogen ρ77. The greater the difference in the purity of the fusible metal, the more their values ρ77 were different. Thus, the authors substantiated the possibility of a qualitative assessment of the purity of metals using contactless measurement and comparison of ρ77 for samples obtained after growing and various deep purification procedures.

Peritectic Intermetallic Compound (IMC) Morphology of Transient Liquid Phase Solder - A Short Review

Transient Liquid Phase (TLP) has been a potential bonding technique for high temperature application solder alloy. TLP bonding for solder is a soldering method that using a low and high temperature metal layer for solid form solder, and a mixing of low and high temperature metal powder in flux medium, for paste form solder. Transient Liquid Phase bonding process involved thoroughly consumption of low melting point metal into high melting point metal and results in the formation of high temperature melting point peritectic intermetallic compound (IMC) which enables the solder to be soldered at typical low soldering temperature but, the solder connection can be applied in the high temperature application. The morphology of the peritectic IMCs mainly consist two solids, which is primary α as well as peritectic β together with liquid phase at peritectic temperature. The growth formation of those primary α and peritectic β phases has resulted with a variety of possible peritectic microstructure’s morphology as will be discussed further.

High-speed visualization measurement for breakup process of liquid metal with solidification

In recent years, Additive Manufacturing (AM) technology such as 3D printing has attracted much attention. In order to produce high-quality metal powders as printing materials, it is necessary to elucidate the phenomena of liquid metal splitting accompanied by solidification, which is manifested in the powder manufacturing process. So far, various experiments have been conducted on the atomization method, but the mechanism for determining powder properties has not been clarified. In particular, there is insufficient knowledge about the phenomenon of molten metal splitting along with solidification. Therefore, in this study, we investigate the breakup process of a single ligament of 42Sn-58Bi, which is a kind of fusible alloy with a melting point of 139 ℃. A high-speed camera is used to visualize the pinch-off process of the ligament. The variation of the neck diameter of the ligament is traced during the fragmentation process. When the initial temperature is high, we found that the neck diameter thins down following a power law of 2/3, corresponding to the trend derived from capillary time scale. On the other hand, as the initial temperature gets lower, the neck diameter becomes thinner than that predicted by the capillary time scale just before breaking up, which is attributed to the influence of solidification.

干热干冷环境对车用易熔合金影响研究

干热干冷环境对车用易熔合金影响研究

Enhanced Hydrogen Generation Performance of Al-Rich Alloys by a Melting-Mechanical Crushing-Ball Milling Method.

The main problem for the application of hydrogen generated via hydrolysis of metal alloys is the low hydrogen generation rate (HGR). In this paper, active Al alloys were prepared using a new coupled method-melting-mechanical crushing-mechanical ball milling method to enhance the HGR at room temperature. This method contains three steps, including the melting of Al, Ga, In, and Sn ingots with low melting alloy blocks and casting into plates, then crushing alloy plate into powders and ball milling with chloride salts such as NiCl2 and CoCl2 were added during the ball milling process. The microstructure and phase compositions of Al alloys and reaction products were investigated via X-ray diffraction and scanning electron microscopy with energy dispersed X-ray spectroscopy. The low-melting-point Ga-In -Sn (GIS) phases contain a large amount of Al can act as a transmission medium for Al, which improves the diffusion of Al to Al/H2O reaction sites. Finer GIS phases after ball milling can further enhance the diffusion of Al and thus enhance the activity of Al alloy. The hydrogen generation performance through hydrolysis of water with Al at room temperature was investigated. The results show that the H2 generation performance of the Al-low-melting point alloy composite powder is significantly higher than the results reported to date. The highest H2 generation rate and H2 conversion efficiency can reach 5337 mL·min−1·g−1 for the hydrolysis of water with 1 g active alloy.

Experiments of melt jet-breakup for agglomerated debris formation using a metallic melt

In severe accidents in a light water reactor, the relocated molten core (so-called corium or melt) can form a debris bed. The debris bed coolability is a critical issue for prevention and mitigation of the molten core–concrete interactions. Agglomeration has a serious impact on assessment of debris bed coolability if agglomeration forms massive debris (so-called agglomerated debris) by merging of melt particles with others when the melt particles accumulate on a floor. This paper presents the results of melt jet-breakup experiments for agglomerated debris formation using a simulant metallic melt. The experiments injected a melt jet of a low-melting point metal through a circular nozzle into a test section filled with coolant water. The particles were generated due to the melt jet-breakup accumulated on to a catcher, which is a flat plate made of stainless steel, installed in the test section. A high-speed video camera imaged particle formation and accumulation on the catcher plate. Agglomerated debris was confirmed by morphological investigation of the recovered debris. The experimental results revealed the effects of the melt jet injection conditions (melt temperature, coolant temperature, and coolant depth) on the mass fraction of agglomerated debris. On the basis of the experimental results, we proposed a simple correlation to estimate the mass fraction. The simple correlation successfully reproduced the mass fraction of agglomerated debris obtained in the DEFOR-A test [Kudinov et al., Nucl. Eng. Des., 301 (2013), 284–295]. The experimental data base presented in this paper makes further contributions to the modeling and validation of mechanistic models or simulation tools for agglomerated debris formation.

Densification, microstructure and properties of Sc and Zr modified Al-Mn alloy prepared by selective laser melting

In this work, the selective laser melting (SLM) of Sc and Zr modified Al-Mn alloy was systematically investigated, with a particular emphasis on the density behavior, microstructure and mechanical properties. The process parameters were significantly impact on the relative density and the maximum relative density of SLM-processed Al-Mn-Sc-Zr specimens reached 99.8% at the optimized process parameters. With the reduction of energy density, the melting mode of melting pool changed from keyhole mode to conduction mode. At the high energy density, near-spherical pores were generated because of the evaporation of low melting alloy constituents. With the decreasing of energy density, irregular pores were generated, which was mainly caused by the insufficient energy input. The SLM processed Al--Mn-Sc-Zr showed a duplex grain microstructure consisting of regions of columnar grains and equiaxed grains. Good mechanical properties were reached in as-fabricated condition: tensile strength ≥ 426 MPa and elongation to fracture ≥ 18%. Besides, no significant anisotropy was found in the stress–strain behavior between horizontal and vertical building direction.

Numerically modelled study of the plunge stage in friction stir spot welding using multi-tiered mesh partitions

Friction stir spot welding is a solid-state joining process that has attracted significant attention particularly in the field of joining of lightweight, low melting alloys. These materials include alloys of Aluminium and Magnesium amongst many others which are of great importance to the aerospace and the automobile industries. The friction stir spot welding is a complex thermo-mechanical multiphysics phenomenon and is currently a field of intense research. The motivation of the current study is to understand this complex behaviour of the joining process by simulating it in the ABAQUS CAE environment. In the friction stir spot joining technique, the plunge stage is identified as the critical stage of operation as it involves a highly transient and dynamic zone for material and temperature flows. The plunge stage was studied in detail using the finite element based model. The plasticity of the material was simulated by the Johnson-Cook material model while the frictional heat generation was captured by applying a penalty-based frictional contact between the rotating tool and the workpiece contact surfaces. Considering the reasonable assumptions made, the results obtained by the numerical simulation model were found to agree with the past experimental and numerically modelled studies.

Study on the hydrogen generation performance and hydrolyzates of active aluminum composites

In this paper, aluminum (Al) composites with low melting point metal bismuth (Bi) and bismuth oxide (Bi2O3) are prepared to realize great hydrogen generation capacity by the ball milling method. The hydrogen generation of Al–Bi composite reacts with water (the initial temperature is 35 °C) can reach 1120 mL/g. The Al–Bi–Bi2O3 produces 1140 mL hydrogen within 2 min by simply raising the initial water temperature to 55 °C. The hydrolyzates of the Al composites are collected and characterized. It indicates that the hydrolyzate of Al–Bi composite mainly includes AlOOH (boehmite), while for the Al–Bi2O3 the hydrolyzate is Al(OH)3 (gibbsite). The scanning electron microscope (SEM) images suggest that the AlOOH particles have more pores than Al(OH)3 particles, which benefit for hydrogen escaping from the hydrolyzate particles surface and for inner Al contacting with water. The Al(OH)3 particles easily accumulate and form a dense layer on the surface of Al particles, which inhibits the hydrogen generation.

Improvement of mechanical properties of magnetostrictive Tb-Dy-Fe alloys via preparing sintered material with low-melting Dy-Cu alloy binder

Direction solidified Tb-Dy-Fe alloys exhibit excellent magnetostrictive properties. However, the applications of Tb-Dy-Fe alloys are limited by the brittleness of Laves phase (Tb,Dy)Fe2 leading to fracture failure and cracking failure. Herein, a novel sintered Tb-Dy-Fe/Dy-Cu compacts were designed and fabricated. The low-melting ductile DyCu phase as intergranular phase or a “binder” was formed in the sintered Tb-Dy-Fe/Dy-Cu compacts. The DyCu phase coated the matrix (Dy,Tb)Fe2 phase grains through a semi-coherent interface and improved the mechanical properties of sintered Tb-Dy-Fe/Dy-Cu compacts. The sintered Tb-Dy-Fe/Dy-Cu compacts showed 176 MPa in bending strength, 3.98 MPa·√m in fracture toughness, 71.3 MPa in tensile strength, and 1186 ppm in the magnetostriction. Compared with the direction solidified Tb-Dy-Fe alloys, significant improvement of mechanical properties was achieved in the sintered Tb-Dy-Fe/Dy-Cu compacts. Furthermore, the high magnetostriction of sintered Tb-Dy-Fe/Dy-Cu compacts was attributed to the<111>orientation which was obtained under an externally oriented magnetic field of 1 T during the forming process.

Mathematical Model of Micropolar Lubricant Considering Viscosity-Pressure Dependence

In the study, based on the micropolar fluid flow equation for a “thin layer”, the continuity equation, the equation describing the profile of the molten contour of the guide coated with a low-melting metal alloy, and the equation for the mechanical energy dissipation rate, asymptotic and exact self-similar solution has been found for the zero (without considering the melting) and first (considering the melting) approximation of wedge-shaped support with the slider support profile adapted to the friction conditions and the low-melting metal coating of the guide surface. The research has taken into account the pressure dependence of the lubricant rheological properties and the melt having micropolar properties in the laminar flow regime. Analytical dependencies have been obtained for the molten surface profile of the low-melting metal coating of the guide and the field of velocities and pressure for the zero and first approximations. Also, the basic performance characteristics of the friction pair under consideration have been determined: the bearing capacity and the friction force. The impact of parameters determined by the coating melt, adapted to the support profile friction conditions, and the parameter characterizing the pressure dependence of the lubricant viscosity on the bearing capacity and friction force has been estimated.

Computational Model for Radial Plain Bearing with Non-Circular Bearing Surface Profile and Fusible Coating on Shaft Surface

The paper presents a study based upon: a Newtonian fluid flow equation (“thin layer”), a continuity equation, and an equation of the molten-profile radius for a shaft coated with a fusible metal alloy; considering a mechanical energy dissipation rate formula, the authors produced an asymptotic and accurate automodel solution for the zero approximation (melting ignored) and first approximation (adjusted for melting) of a radial plain bearing featuring a fusible metal coating and a bearing profile adapted to the specific friction parameters. The paper further presents analytical dependencies describing the molten surface radius, velocity and pressure fields for zero and first approximation. Besides, it determines the key operating parameters of the frictional couple, the bearing capacity, and the friction. It also shows how the parameters arising from the melting of the surface affect the bearing capacity and friction where the bearing surface profile is adapted to the specific conditions of friction.

Hierarchical heterostructured FeCr–(Mg–Mg2Ni) composite with 3D interconnected and lamellar structures synthesized by liquid metal dealloying

Liquid metal dealloying (LMD) has recently attracted significant attention. Because the LMD process enables the production of three-dimensional (3D) interconnected non-noble metallic materials. In addition, the metallic melt medium is useful for the development of heterostructure (HS) metal–metal composites. However, the solidified liquid metal phase (low melting point metals such as Mg, Bi, Sn, or Cu) has a much lower strength than the developed ligament phase (e.g., Fe, FeCr, Ti, etc.). In this study, the soft Mg phase was strengthened by adding alloying element of Ni. A eutectic composition of Mg–10 at.% Ni melt leads to the formation of fine eutectic structure of (Mg–Mg2Ni) within 3D interconnected morphology. This hierarchical heterostructured composite consisted of FeCr ligament and Mg–Mg2Ni lamellar, and a high yield strength of 280 MPa and a noticeable elongation (1.5%) were achieved. The complex 3D morphology of ligament and lamellar geometrically constraint each other, and it prevents the early fracture of brittle Mg–Mg2Ni lamellar phase. The alloy design for the LMD melt gives insights for hierarchical HS materials with outstanding mechanical properties for structural applications.

Study on the Middle Bronze Age Disc-Butted Axe Ornament from Archaeometallurgical Point of View

Our research was conducted on a copper disc-butted axe, with a surface decoration made of a tin-based alloy, which was found east of the Carpathian Mountains in the Moldavian Plateau. This unique piece is thought to belong to the Middle Bronze Age in the Western Carpathians—Wietenberg, Suciu de Sus and Otomani–Füzesabony cultures. In order to evaluate the application process and the origin of the ores used, the surface and volume phase variation of the concentration of the metal components of the basic alloy (copper) and of the ornament was analysed using optical microscopy (OM), stereomicroscopy (SM) and SEM-EDX. The archaeometric features, formed both during its use and during its lying in the archaeological site, were identified and later used in archaeometallurgical evaluations and in determining the preservation condition of the two components (axe and ornament) on the surface, interface and in stratigraphic section. Experimental data revealed that, after its casting in porous silicon stone moulds, the object was coated with a thin film by immersion in an easily fusible tin alloy, which included copper as the major alloying component and arsenic and iron as minor components. After finishing the shiny white coat, a beautiful decoration was applied by incision and engraving. Used as a battle axe, it also had a rank function, as it belonged to the community leaders. The data prove the ability of ancient craftsmen to design and process copper alloys to obtain authentic extremely beautiful artefacts, which provide new possibilities to reveal the social and symbolic function of certain ancient bronze objects.

Influence of rheological behavior on wall thickness using low-melting alloy for sheet metal forming

The wrinkling-free forming method for sheet metal forming based on the low-melting alloy (LMA) is a novel sheet forming method. The LMA as a forming pressure medium to transfer loading force is utilized to prevent bulking and wrinkling occurrence in the sheet forming process due to the its controllable fluidity by adjusting the heating temperature. In the forming process, the upper and lower surface of blank were acted by continued loading force resulting from LMA flowing. In this study, the high-temperature mechanical properties of LMA were obtained by heating tensile test for preparation of simulation. The rheological behavior of LMA during the forming process was analyzed numerically. And the effect of LMA layer thickness, forming force and mold structure on the thinning of the formed parts was studied. With obtained results, the characteristic of wall thickness distribution and the effect of rheological behavior on thinning of formed part were comprehensively revealed. Moreover, the experimental results agree with those in numerical simulation by measuring the wall thickness of the formed specimen.

Computational model of a micropolar lubricant with a non-standard support profile and a metal coating at incomplete filling of the working gap

The authors propose an asymptotic and exact self-similar solution for zero (without considering the melt) and the first (considering the melt) approximation of a wedge-shaped sliding support with a profile adapted to friction and a fusible metal coating of the guide surface. The solution is based on the equation of a micropolar liquid flow for a “thin layer”, the continuity equation, as well as the equation describing the profile of the molten contour of a guide coated with a fusible metal alloy. The authors have taken into account the formula of the rate of mechanical energy dissipation as well as rheological properties of the lubricant and the melt, which have micropolar properties in the laminar flow mode at incomplete filling of the working gap. Analytical dependences have been obtained for the profile of the molten surface of the guide coated with a low-melting metal alloy, as well as for the velocity and pressure fields at zero and first approximation. In addition, the main operating characteristics of the friction pair under consideration have been determined: the bearing capacity and the friction force. The article contains estimation of the influence of the parameters conditioned by coating melt and adapted to the friction conditions of the support profile, and the parameter characterizing the rheological properties of the lubricant, as well as the length of the loaded area in terms of bearing capacity and friction force.

Semi-theoretical correlations of melting process driven by Rayleigh–Bénard convection suitable for low melting point metal

This paper studies the melting process of low melting point metal (LMPM) in a square cavity heated from bottom in the presence of Rayleigh–Bénard convection. Existing research focuses on high–Pr PCM melting process, and the difference between low and high-Pr PCM melting process needs to study. Scale analysis and numerical investigation are applied to analyze low-Pr LMPM melting process. Scale analysis tries to research the LMPM melting rate and obtain basic theoretical relationships of liquid fraction and Nu with Fo, Pr, Ras and Ste. A numerical model is established to elaborate dynamic melting heat transfer characteristics of low–Pr LMPM. The numerical results show that different from high-Pr PCM, the flow cell morphology presents obvious changes for low-Pr LMPM, and the time needed to completely melt is much shorter and the average heat flux is higher. The Rayleigh–Bénard convection causes oscillation of Nu in the convection dominated regime, and the average Nu for LMPM increases from 5.11 to 13.77 with the Ra from 5.0×105 to 1.25×107. Finally, the semi-theoretical correlations for liquid fraction and Nu are developed by scale analysis and numerical investigation, and the accuracy is numerically validated.

Heterogeneous nucleation of gallium with lattice-matched cubic carbide and nitride phases

Energetic barriers to nucleation can result in metastable liquids, which require additional undercooling to initiate solidification. Gallium, a low melting point metal of potential use as a phase change material and for liquid metal electronics, exhibits a well-documented temperature-dependent undercooling that can exceed 60 °C in small volumes (10 μl) cooled at moderate cooling rates (10 °C/min). Here, we use an epitaxial lattice-matching technique to identify cubic carbide and nitride phases that could serve as nucleation catalysts for gallium and gallium-based eutectics. We demonstrate multiple cubic carbides and nitrides that reduce undercooling and show that the relationship between the lattice mismatch and observed undercooling conforms with the heterogeneous nucleation theory. HfC and ZrN result in the smallest reported undercooling to date, &amp;lt;20 and &amp;lt;10 °C, respectively, across all equilibration temperatures after aging. These materials remain stable, even after aging for 120 days in liquid Ga. The carbide and nitride phases described here are commonly used as hard coatings and diffusion barriers, suggesting their practical applicability as thin coatings that both protect an underlying device or component and simultaneously reduce undercooling of gallium or gallium-based eutectics.

PEGylated Indium Nanoparticles: A Metallic Contrast Agent for Multiwavelength Photoacoustic Imaging and Second Near-Infrared Photothermal Therapy.

Indium, a low melting point metal, is well-known for constructing eutectic gallium-indium liquid metal. However, unlike liquid metal nanoparticles, the biomedical applications of metallic indium nanoparticles (In NPs) remain in their infancy. Herein, an ultrasound-assisted liquid-reduction synthesis strategy was developed to prepare PEGylated In NPs, which were then used as a high-performance contrast agent for enhancing multiwavelength photoacoustic imaging and second near-infrared (NIR-II) photothermal therapy of the 4T1 breast tumor. The obtained In NPs depicted remarkable optical absorption from the first near-infrared (NIR-I) to NIR-II region and a high photothermal conversion efficiency of 41.3% at 1064 nm, higher than the majority of conventional NIR-II photothermal agents. Upon injection into the tumor, the photoacoustic intensities of the tumor section post-injection were obviously increased by 2.59-, 2.62-, and 4.27-fold of those of pre-injection by using excitation wavelengths of 750, 808, and 970 nm, respectively, depicting an excellent multiwavelength contrast capability of photoacoustic imaging. In addition, efficient ablation of the 4T1 tumor was achieved through the photothermal performance of PEGylated In NPs under NIR-II laser irradiation. Importantly, as the widely used element in the clinic, In NPs were highly biocompatible in vitro and in vivo. Therefore, this work pioneered the biomedical applications of PEGylated In NPs for cancer diagnosis and treatment.