Low Melting Temperature Alloy Research Articles

Enhancement on heat transfer and reliability of low melting temperature alloy based thermal interface materials

In this paper, the thermal contact resistance (TCR) of different kinds of thermal interface materials (TIMs) is experimentally investigated. The effect of contact pressure on the thermal resistance of low melting temperature alloy (LMTA) TIMS on different metal substrates has been analyzed in detail. The TCR of all TIMs decreases with the rise of contact pressures. At higher contact pressures, however, the decreasing trend of TCR becomes less pronounced. The adsorption of LMTA by perforated copper foil substrate (PCFS) and copper mesh substrate (CMS) at very high contact pressures removes the leakage phenomenon. However, its thermal resistance is higher than that of samples with a single layer of copper foil substrate (CFS). The PCFS was then parametrically analyzed to obtain the PCF porous ration and LMTA brush weight with the lowest thermal resistance. The results revealed that the TIM samples with a single copper foil substrate exhibited the lowest TCR, but at high pressures, the LMTA is flooded and pumped out. Three different PCFSs were made with 1 mm diameter surface holes and 1.5 mm, 2 mm and 2.5 mm center distances between adjacent holes. All three PCFSs yield the lower thermal resistance than samples with a single layer of CFS at the optimum brush applied LMTA weight. The lowest thermal resistance was achieved by brushing 1.018 g weight of LMTA on a PCF with 19.63% porous ration. The thermal resistance of this sample is only 0.12736 cm2·K·W−1 at 24 MPa.

Three-dimensional printability of bismuth alloys with low melting temperatures

Equipment that can produce high thermal energy and provide controlled environmental conditions is required to use metals in three-dimensional (3D) printing technology. As a result, the costs of this equipment are relatively high. However, the potential for using simpler equipment for the 3D printing of alloys with low melting temperatures is remarkable. In this study, the printability of parts from low melting temperature alloys with a 3D printer using the fused deposition modeling (FDM) technique was investigated. Alloys with chemical compositions of Bi50Pb26.7Sn13.3CD10 and Bi50Pb25Sn25 were fabricated by FDM. The physical and mechanical properties of samples fabricated by FDM and conventional casting were then investigated. According to the data obtained, samples produced using FDM have lower tensile strength compared to traditional casting but show a greater elongation.

Hybrid thermal management strategy with PCM and insulation materials for pulsed-power source controller in extreme oil-well thermal environment

• Thermal management strategy for PPS controller are experimentally investigated. • Metal PCM can lower thermal resistance from 1.7 to 1.1 K/W compared to paraffin. • Silica aerogels can alleviate heat transfer from external environment by 59.9%. • Chip operating time can be prolonged when using present thermal management strategy. The application of pulsed-power source (PPS) can effectively improve the efficiency of shale oil exploitation. However, the severe underground environment with high temperature, pressure and viscosity will bring great challenges to electronic components. This study presents a hybrid thermal management strategy (HTMS) for the PPS controller. The heat storage unit filled with phase change materials (PCMs) is applied for internal thermal management, and the performance of PPS is evaluated when paraffin and low melting temperature alloy (LMTA) are respectively used as PCMs. On the other hand, glass wool, phenolic foam and silica aerogels are implemented to construct a sandwich structure for external thermal protection. Results show that the LMTA can extend the safe operating time of equipment from 50 min to over 250 min in comparison to paraffin while lowering the average equivalent thermal resistance from 1.7 K/W to about 1.1 K/W. Besides, the application of glass wool and phenolic foam is eligible to extend the operating time by 63 % and 57 %, respectively, with external ambient temperature at 100 °C. After replacing by the silica aerogels, the thermal insulation effect can be further improved. As the result, with the application of HTMS, the PPS controller is tested under more severe thermal environment with ambient temperature of 150 °C. It is noticed that the operating time prolongs to 50 min within the maximum junction temperature of 80 °C.

Study of structural, physical, characteristics and radiation shielding parameters of Bi50-Pb40-Sn10 and Bi40-Pb40-Sn10-Cd10 alloys used for radiation therapy

This work is carried out for the development of radiation shielding block alloys (bismuth based) for radiation therapy. Two different bismuth alloys whose composition, first, Bi-40 wt.% Pb-20 wt.% Sn and secondly, Bi-40 wt.% Pb-10 wt.% Sn-10 wt.% Cd are known as low melting temperature alloys (named fusible alloys). These alloys are used for the protection of vital critical organs inside the radiated area during radiotherapy applications. Structure, mechanical properties, and radiation shielding parameters of prepared alloys by conventional and rapid quench from molten state using the melt-spun technique have been studied and analyzed. It is concluded that from x-ray diffraction analysis, the presence of a new metastable crystalline phase (hexagonal structure a = 3.505, b = 3.505 and c = 5.795 nm) called Pb7Bi3 is detected. The formation of a metastable crystalline phase Pb7Bi3 causes the enhancement of mechanical properties. It is also concluded that the bismuth alloy which is cadmium-free exhibits superior microhardness compared to bismuth alloy containing cadmium. The measurements of radiation parameters were taken using 60Co and 6 MV. X-ray shows that alloy-free Cd has good attenuation coefficient, good mechanical characteristics, Vickers microhardness and moderate melting temperature. We can easily synthesise the bismuth alloy cadmium-free into suitable shapes in addition to it being friendly to the environment (green environment), so that they may be used as a substitute candidate instead of bismuth alloy containing Cd to use in radiation therapy.

Design Principles and Applications of Next-Generation High-Energy-Density Batteries Based on Liquid Metals.

Increasing need for the renewable energy supply accelerated the thriving studies of Li-ion batteries, whereas if the high-energy-density Li as well as alkali metals should be adopted as battery electrodes is still under fierce debate for safety concerns. Recently, a group of low-melting temperature metals and alloys that are in liquid phase at or near room-temperature are being reported for battery applications, by which the battery energy could be improved without significant dendrite issue. Besides the dendrite-free feature, liquid metals can also promise various high-energy-density battery designs on the basis of unique materials properties. In this review, the design principles for liquid metals-based batteries from mechanical, electrochemical, and thermodynamical aspects are provided. With the understanding of the theoretical basis, currently reported relevant designs are summarized and analyzed focusing on the working mechanism, effectiveness evaluation, and novel application. An overview of the state-of-the-art liquid metal battery developments and future prospects is also provided in the end as a reference for further research explorations.

Investigations regarding the influence of soft metal and low melting temperature alloy on thermal contact resistance

In this paper, the thermal contact resistance (TCR) of thermal interface materials (TIMs) is experimentally investigated. The effects of contact pressure, heating load and surface roughness are examined in details. Results shows that the low melting temperature alloy (LMTA) can pronouncedly improve the TCR at high heating load condition when compared to indium TIM. Meanwhile, a larger contact pressure or a smoother interface also reduce the TCR effectively. For the solid-state indium TIM, an apparent hysteresis effect is seen for the TCR against contact pressure while there is no hysteresis effect regrading TCR against heating load. The indium TIM is reduced from 0.141 K·W−1 to 0.119 K·W−1 after loading and unloading of contact pressure, showing an apparent hysteresis effect. On the other hand, the TCR of LMTA can be improved by about 13.9–16.0% after increase/decrease heating process. Yet, LMTA contains some overflow issue upon melting. Hence a novel design of LMTA with indium confinement seal is proposed to eliminate overflow problem. Through this design, the TCR remains barely unchanged even after hundred cyclic operations. Additionally, a correlation for predicting the TCM of solid-state TIMs is proposed, and the correlation can predict 98% of experimental data within the error of ±30%.

Feasibility of a Mitral Annuloplasty With the Capability for Peri- and Postoperative Adjustment

Abstract Surgical repair with implantation of a mitral annuloplasty ring is the gold standard treatment for mitral regurgitation. However, outcomes are variable and recurrent mitral regurgitation is not uncommon. A REshapeable Mitral Annuloplasty DevIce (REMADI) is proposed, which consists of a fully encapsulated low melting temperature alloy. The alloy is solid and rigid at body temperature and provides traction force to shape the annulus. When heated using a noncontact method, the alloy melts and the REMADI becomes malleable. The REMADI is engaged with the mitral valve annulus using anchors which automatically deploy upon contact. A passive beating porcine heart model was used to demonstrate the feasibility of the REMADI device, which was deployed, engaged, and used to reduce the diameter of the mitral valve annulus.

Microstructure refinement for superior ductility of Al–Si alloy by electron beam melting

Refining the microstructure to improve the ductility of an Al‒Si alloy is challenging. In this paper, we report for the first time a novel microstructure refinement approach for AlSi10Mg (wt%) alloys using electron beam melting (EBM) technology, without the addition of any modification elements. The synergetic effect of superheating, fast cooling, and preheating contributes to a refined Si phase with a fine granular structure (0.5–2 μm) within bimodal Al grains (40 μm grains and 0.5–2 μm sub-grains). The results provide good evidence for the proposed refinement mechanism. A maximum ductility of approximately 32.7 % with a tensile strength of approximately 136 MPa was achieved for the as-built AlSi10Mg EBM alloy. After solution heat treatment and T6-like aging, nano-Si precipitates formed which strengthened the alloys. The pathway developed in this study for refining the Al–Si alloy microstructure to improve the tensile ductility will provide a feasible and fast manufacturing method for improving the microstructure and mechanical properties of other low-melting temperature alloys in the near future using EBM technology.

Investigation on the induction stirring effect in a laboratory scale crucible with the variation of electrical supply parameters

Purpose This paper aims to study the possibility of controlling the electromagnetic stirrer (EMS) is fundamental in a continuous casting line to achieve the desired properties of homogeneity and mechanical strength in the solidified cast. Design/methodology/approach Coupled electromagnetic (EM) and fluid dynamic (FD) simulations allow to predict the mixing effect on molten metal, in terms of velocity amplitude and shape of the flow. This paper describes the numerical results of EMS effect within a cylindrical crucible, surrounded by a solenoidal inductor, filled with a low melting temperature alloy, i.e. GalInStan. Findings Induced forces and resulting velocity distribution of the flow of the liquid metal have been calculated depending on varying amplitude and frequency of the supplied current. As expected, at a given amplitude of the current supply, the velocity distribution shows a maximum at a certain frequency while the intensity of electrodynamic forces monotonically increase as the frequency increases Originality/value The paper deals with simply models and experiments applied to coupled EM and FD problem, to assess the applied methodology.

Experimental Study on Thermal Contact Resistance Improvement for Optical Fiber by Using Low-Melting Temperature Alloy

Abstract This paper presents an experimental analysis for minimizing the thermal contact resistance (R) between an optical fiber and copper heat sink by using the low-melting temperature alloy (LMTA) as the thermal interface material (TIM) subject to high-flux operation (up to 250 W ⋅ m−1). For the cases without LMTA, the temperature rise (ΔT) can easily surpass 195 °C at a heating load of 25 W ⋅ m−1. By contrast, ΔT is dramatically reduced to be less than 1 °C with LMTA as TIM with a much higher heating power of 150 W ⋅ m−1. The corresponding thermal resistance (R) can be reduced from 6.5–8.2 K ⋅ m ⋅ W−1 to 0.004–0.013 K ⋅ m ⋅ W−1. The improvement is far superior to existing studies. Besides, decreasing the surface roughness and increasing contact pressure also help to reduce R, especially for the cases when the LMTA is not melted. As the LMTA melts, a significant reduction of R by 56% is achieved as compared to the case without melting. The effect of surface roughness and contact pressure on the thermal contact resistance is also examined, and it is found that the influences are small once LMTA melts.

Utilization of low-melting temperature alloy with confined seal for reducing thermal contact resistance

This paper investigates a novel design of thermal interface material (TIM) using low-melting temperature alloy (LMTA) with confined seal. For solid TIM like indium foil, the thermal contact resistance is reduced with the rise with contact pressure, and an apparent hysteresis phenomenon may occur during loading/unloading of contact pressure. For the solid-state TIM, the indium TIM outperforms those of copper, lead and tin TIMs. The molten LMTA can further reduce the thermal contact resistance, however, the overflow and dislocation problems are observed. Hence, a novel confined design by using LMTA with an annular metal seal is proposed that can completely prevent aforementioned problems. Yet the reliability of the novel TIM is also investigated after hundred thermal cycles.

Numerical Simulation of Brazing Aluminium Alloys with Al–Si Alloys

Joining parts using low-melting temperature alloys has long been used for manufacturing complex components such as heat exchangers made of aluminium alloys. Investigations of the process have shown that core/ clad interaction during heating and brazing can lead to a significant decrease in the amount of liquid available for joint formation. This study presents a transient one-dimensional model for the process that takes into account the diffusion of silicon and the movement of the core/clad interface, with the model equations being implemented in the finite element software COMSOL Multiphysics; the results are compared to literature experimental data. Silicon profiles in the core are well described, while there appears a significant difference between predicted and experimental values of remaining clads which suggest a strong effect of silicon diffusion and liquid penetration at core grain boundaries.

Interfacial reactions in molten state micro solder joints under current stressing

The high local temperature in flip-chip solder joints of microprocessors has raised concerns that the solder, a low melting temperature alloy, might locally liquefy and consequently cause failure of the micro solder joint. This article reports the electromigration (EM) behavior when the solder is in the molten state. The electronic current was applied to the Cu/Sn-3.0Ag-0.5Cu (SAC305)/Cu molten solder joints. The growth of the intermetallic compound (IMC) and the consumption of the Cu pad were investigated. Moreover, the transition of IMC 3-D morphologies was also studied by the deep-etching method after EM test. The results of the electromigration in the molten solder joints indicate that the growth of the interface IMC and the consumption of the Cu pad present similar trends with those in the solid state micro solder joints, however, the rates of the growth and consumption are higher than those in the solid state micro solder joints. The evolution of IMC 3-D morphologies during the electromigration in the molten solder joints shows its own unique features, which are different from the electromigration in the solid state solder joints. With the increase of stressing time, the IMC 3-D morphologies transition indicates that the average grain size of cathodic Cu6Sn5 increases in radial direction with the increase of stressing time, but the size first increases, and then decreases in axial direction. In contrast to the morphologies transition for cathodic Cu6Sn5, the average grain size of anode Cu6Sn5 increases not only in radial direction but also in axial direction.

Effect of the solidification time on the median particle size of powders produced by water atomisation

Present empirical correlations to predict the median particle size of water atomised powders have a validity restricted to a particular atomiser and alloy family. This work proposes a mathematical function that takes into account the influence of the heat transfer coefficient and, therefore, of the solidification time on the median particle size. This equation is applied in combination with previously proposed empirical correlations to extend their validity to a broader range of alloys. Experiments were conducted with alloys of different melting point (Fe base, Cu base and Sn). Quantitative measurements of the median particle size, tap density and several shape factors, and qualitative observations of the particle shape confirmed the importance of the heat transfer rate. It is shown that the inclusion of the solidification time effect results in a better agreement between calculated and experimental data when both low and high melting temperature alloys are taken together.

Thermal performance of low melting temperature alloys at the interface between dissimilar materials

This paper describes the thermal performance and practical concerns of using a variety of thermal interface materials (traditional: greases, phase change materials, gels, and thermal pads; emerging: carbon nanotubes, graphene, low melt alloys, and metallic nanosprings) and investigated the reliability of low melt alloys (LMAs) containing gallium, indium, bismuth, and tin as thermal interface materials (TIMs). The analysis presented herein involved the thermal performance evaluation of LMAs placed between different surfaces (copper and nickel) after accelerated life cycle testing, which included high temperature aging at 130 °C and thermal cycling from −40 °C to 80 °C. Three alloys (75.5 Ga and 24.5 In, 100 Ga, and 51 In, 32.5 Bi, and 16.5 Sn) were chosen as candidate LMA TIMs. The testing methodologies followed ASTM D5470 protocols. Measurements showed that the proposed alloys survived as long as 3000 hours of aging at 130 °C and 1500 cycles from −40 °C to 80 °C without significant thermal performance degradation. The obtained results show that the performance of LMAs is significant as TIMs.

Accelerated aging and thermal cycling of low melting temperature alloys as wet thermal interface materials

This paper focuses on developing an effective thermal interface material (TIM) using low melt alloys (LMAs) containing gallium (Ga), indium (In), bismuth (Bi) and tin (Sn). The investigation described herein involved the thermal performance evaluation of LMAs after accelerated life cycle testing, which included isothermal aging at 130°C and thermal cycling from -40°C to 80°C. Three alloys (75.5Ga/24.5In, 100Ga, and 51In/32.5Bi/16.5Sn) were chosen as candidate LMA TIMs. The testing methodologies followed ASTM D5470 protocols and the performance of the alloys was compared to commercially available thermal grease and liquid metal TIMs. To understand the LMA-substrate interactions, the alloys were applied to different surfaces (bare copper, nickel coated copper and tungsten coated copper). It was found that the proposed alloys between bare copper substrates were able to survive as long as 2700h of aging at 130°C and 1400cycles from −40°C to 80°C without significant performance degradation.

Investigation into the application of low melting temperature alloys as wet thermal interface materials

The application of low melt alloys (LMAs) containing In, Ga, Sn, and Bi as compliant high performance thermal interface material (TIM) is investigated. The investigation described herein involves in situ thermal performances of the LMAs as a function of applied pressure and interface temperature, performance evaluation after accelerated life cycle testing, and guidelines to improve the cycle life. Testing methodologies follow ASTM D5470 protocols, and measurements are validated by testing well established, commercially available TIMs and comparisons are made to values reported in open literature as well as manufacturers’ data. Measurement shows that LMAs can offer thermal interfacial resistances as low as 0.005cm2°C/W, and their performance is highly contingent upon the quality of the mating surfaces. The issue of LMA containment and dewetting are discussed along with the solutions to mitigate them.

Thermal Performance of Low-Melting-Temperature Alloy Thermal Interface Materials

Thermal resistance of low-melting-temperature alloy (LMTA) thermal interface materials (TIMs) was measured by laser flash method before and after different stages of heating. The results showed that the thermal performance of the LMTA TIMs was degraded during the heating process. It is suggested that the degradation may mainly be attributed to the interfacial reaction between the Cu and the molten LMTAs. Due to the fast growth rate of intermetallic compound (IMC) at the solid–liquid interface, a thick brittle IMC is layer formed at the interface, which makes cracks easy to initiate and expand. Otherwise, the losses of indium and tin contents in the LMTA during the interfacial reaction will make the melting point of the TIM layer increase, and so, the TIM layer will not melt at the operating temperature.

A18 低融点合金を用いた高速回転主軸用オートバランサ(OS2 最新機械要素技術(4))

Demands for high precision and high efficiency of a machine tool have recently increased. In order to meet such demands, more efficient oscillating control and higher rotational speed of a spindle system are required. In this study, a new balancing method which does not cause an unstable oscillation and enables flexible to change of unbalance is proposed. Based on the proposed method, an auto balancer with the low melting temperature alloy is developed. Experiments are conducted and the performance of the proposed method is evaluated.

Deformation of metallic liquid drop by electric field for contacts in molecular–organic electronics

We study and use the behaviour of a metallic liquid drop in the presence of an external electric field (EF). The droplet profile is governed by the stabilizing surface energy and the destabilizing electrostatic energy, with a critical voltage beyond which the droplet becomes unstable. We explore the EF-induced behaviour of low melting temperature alloy in the liquid state and observe that the droplet modifications in the linear response regime can be retained upon cooling the drop to the solid state. We demonstrate that this procedure can be used as an electrode with precise dimensions for applications in molecular and polymer electronics.