Thickness Of Intermetallic Layer Research Articles

Effect of Ti on Morphology and Growth of Zn–Fe Intermetallic Phases

The effect of Ti in Fe substrate on the morphology and growth of Zn–Fe alloy phases in (Zn–0.2 wt.%Al)/Fe diffusion couples was investigated using optical and scanning electron microscopy. It is shown that ζ phase layer does not exist in (Zn–0.2 wt.%Al)/Fe couple, but it can be clearly observed in (Zn–0.2 wt.%Al)/(Fe–Ti) diffusion couples. Increasing of dissolved Ti in Fe substrate delays the disappearance of the ζ phase and promotes the formation of δk phase. The δp phase grows toward the ζ phase layer in the form of arborescence. The growth of total intermetallic phase layers in all diffusion couples is controlled by diffusion of Zn and Fe atoms within the layers at 380 °C. The thickness of total intermetallic layer increases with increasing of dissolved Ti in Fe substrate and reaches the maximum when Ti content is 0.4 wt.%.

Characterization of intermetallic compound layer thickness at aluminum–steel interface during overlaying

Abstract In this research, the thicknesses of Fe2Al5 sub-layer (lFe2Al5) in bead welds were roughly calculated according to the formula l = Kt1/2. The values of constant K and residence time t were obtained through recording welding pools temperature. Fe2Al5 sub-layers were also observed and their thicknesses were measured by SEM and EDS analysis. The calculated results were in close agreement with measured results, demonstrating the accuracy of these calculated Fe2Al5 sub-layer thicknesses.

Effects on the microstructure and mechanical properties of Sn-0.7Cu lead-free solder with the addition of a small amount of magnesium

Abstract The influence of a small amount of magnesium (only 0.01 wt.%) added to the Sn-0.7Cu solder alloy during the aging process of microstructural evolution is studied along with the mechanical properties of the alloy. The experimental results indicate that the addition of magnesium decreases the tensile strength of the solders but improves their elongation. The solidification structure of eutectic Sn-0.7Cu consists of β-Sn, and the eutectic structure, which has extremely fine intermetallic nodules, Cu6Sn5, is located in the interdendritic region. When the magnesium is added to the Sn-0.7Cu alloy, the Sn dendrites become slightly coarser; in comparison, the melting point of the Sn-0.7Cu-0.01Mg alloy decreased by 2°C for the differential scanning calorimetry results of bulk alloy samples. Sn-0.7Cu-0.01Mg exhibits the lowest contact angles and the widest spreading areas. After aging, the Sn-0.7Cu and Sn-0.7Cu-0.01Mg solders show significant changes in strength, mainly because of the obvious increase in the thickness of the Cu6Sn5 intermetallic layer.

Numerical Simulation of Multilayer Composites Failure under Dynamic Loading

The processes of high-velocity interaction of a projectile with a metal-intermetallic laminate (MIL) composite target were numerically investigated in axisymmetrical geometry using the finite element method. To simulate the failure of the material under high velocity impact, we applied the active-type kinetic model determining the growth of microdamages, which continuously changes the properties of the material and induce the relaxation of stresses. To simulate the brittle-like failure of the intermetallic material under high velocity impact, we modified the kinetic model of failure and included the possibility of failure above Hugoniot elastic limit in the shock wave and sharp drop in strength characteristics if the failure begins. The results show that the depth of penetration depends on the thicknesses of intermetallic and titanium alloy layers. The Al3Ti/Ti-6-4 MIL composite target withstands the impact loading in the case of the ratio about 4/1.

Investigating the thermomechanical properties and intermetallic layer formation of Bi micro-alloyed low-Ag content solders

In our research, we performed comparative analyses concerning various lead-free SAC (Sn96.5Ag3Cu0.5, Sn95.5Ag4Cu0.5) and two types of micro-alloyed SAC (SnAgCu+Bi+Sb) solder alloys. The mechanical properties of these solder alloys were characterised by measuring the shear strength of 0603 (1.5×0.75mm) size chip resistors’ joints. We designed a testboard, which contains fifty pieces of 0603 size resistors for mechanical characterisation and for measuring the thickness of intermetallic layers. During the experiment, twenty-eight pieces of testboards were soldered with vapour phase soldering (seven with each solder alloy) and sixteen of them were subjected to Thermal-Shock (TS) life-time tests with temperature range of +140 to −40°C up to 2000 cycles. The intermetallic layer (IML) formation was investigated with Scanning Electron Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM) methods; and the growth of the layer was analysed by measuring the IML thickness on cross-sectional samples after given TS cycles. It is shown that the thickness of the intermetallic layer in as-reflowed samples (samples without aging) depends on the silver content of the given alloy. Besides, the layer growth rate during Thermal Shock tests is affected by the number of intermetallic layer grain-boundaries along a unit of length.

Effect of intermetallic compound layer thickness on the shear strength of 1206 chip resistor solder joint

Purpose – The purpose of this paper is to study the effect of intermetallic compound (IMC) layer thickness on the shear strength of surface-mount component 1206 chip resistor solder joints. Design/methodology/approach – To evaluate the shear strength and IMC thickness of the 1206 chip resistor solder joints, the test vehicles were conventionally reflowed for 480 seconds at a peak temperature of 240°C at different isothermal ageing times of 100, 200 and 300 hours. A cross-sectional study was conducted on the reflowed and aged 1206 chip resistor solder joints. The shear strength of the solder joints aged at 100, 200 and 300 hours was measured using a shear tester (Dage-4000PXY bond tester). Findings – It was found that the growth of IMC layer thickness increases as the ageing time increases at a constant temperature of 175°C, which resulted in a reduction of solder joint strength due to its brittle nature. It was also found that the shear strength of the reflowed 1206 chip resistor solder joint was higher than the aged joints. Moreover, it was revealed that the shear strength of the 1206 resistor solder joints aged at 100, 200 and 300 hours was influenced by the ageing reaction times. The results also indicate that an increase in ageing time and temperature does not have much influence on the formation and growth of Kirkendall voids. Research limitations/implications – A proper correlation between shear strength and fracture mode is required. Practical implications – The IMC thickness can be used to predict the shear strength of the component/printed circuit board pad solder joint. Originality/value – The shear strength of the 1206 chip resistor solder joint is a function of ageing time and temperature (°C). Therefore, it is vital to consider the shear strength of the surface-mount chip component in high-temperature electronics.

Characterisation of Ni-Ti intermetallic coatings formed on Cp titanium by diffusion treatment

In order to produce a thick near equi–atomic NiTi intermetallic layer on the surface of titanium plate, layers of nickel with thicknesses of 30 µm and 60 µm were electroplated on commercial pure (Cp) titanium and subsequently were heat treated at 850°C and 900°C. The effects of heat treating temperature and the thickness of electroplated nickel on the evolution of the microstructure and mechanical properties were studied. The results confirm the formation of various intermetallic layers in the coatings that substantially affect their hardness. The optimum condition for the formation of a thick NiTi intermetallic layer on the outer surface of the titanium was diffusion treatment of the sample electrodeposited with 30 µm nickel at 900µC for 12 h. The hardness of this layer was found to be 280 HV0.15.

Interfacial reaction of Bi–Ag and Bi–Sb solders on copper substrate with multiple reflow number

Owing to the toxicity of lead, much effort has been put in studies on lead-free solders after environmental legislations prohibited the use of lead in these parts worldwide. Here, Bi–Ag and Bi–Sb alternative solder alloys containing 1·5–5 wt-% Ag and Sb were investigated. The effect of the reflow number and weight percentage of Ag and Sb on the surface properties of solders and interfacial reactions between the solder bulk and the Cu substrate were analysed by optical microscopy and scanning electron microscopy–energy dispersive X-ray. The results show that by increasing the reflow number and wt-% of Ag and Sb in the solder bulk, the thickness of the mechanical grain boundary grooving is increased. However, the thickness of the Cu3Sb intermetallic compound layer at the interface of Bi–5Sb decreased by increasing the reflow number. Moreover, our findings show that the amount of Ag and Sb in solder alloys and the reflow number have different behaviours on the wettability properties. By increasing the reflow number, the wetting angle decreased in Bi–Ag solder alloys, whereas it increased in Bi–Sb solder alloys.

Structure and Properties of Al–Ti Multilayered Composites with Intermetallic Layers

In this paper growingtheintermetalliclayers at the interfaces of explosively welded titanium and aluminum plates have been investigated. It was shown that explosion welding was the efficient technology for forming multilayered stacks consisted of dissimilar materials. This method provided the firm joint formation between metallic plates. Heat treatment of explosively welded workpieces allowed obtaining the Al3Ti intermetallic phase at titanium-aluminum interfaces. Formation of intermetallic layer proceeded inhomogeneously in cross-section of the composite due to the structural particularities of interfaces and adjacent arias formed during the explosion welding process. The titanium aluminide growth ratedecreased corresponding to increaseof the intermetallic layer thickness. Intermetallic phase is notable for its high hardness and elasticity. Microhardness and Young’s module in the composite explosively welded and annealed at 640оС reached 7.5 GPaand 280GPa respectively.

Comparing the reliability and intermetallic layer of solder joints prepared with infrared and vapour phase soldering

Purpose – The purpose of this paper is to compare the reliability and intermetallic layer (IML) of solder joints prepared with infrared (IR) and vapour phase (VP) soldering. The reliability of 0603-sized resistors’ solder joints formed with IR and VP soldering was investigated. The IML of the joints was analysed based on image processing algorithm automatically. Design/methodology/approach – For the reliability analyses, the ageing method was a highly accelerated stress test (HAST) with +105°C maximum temperature, fully saturated (100 per cent) relative humidity at +0.5 atm overpressure. The joints were characterised based on the thickness of their IML and on their shear strength in as-reflowed stage, and after 400, 800, 1,200, 1,600 and 2,000 hours of HAST. An image processing algorithm was developed to measure the thickness of the IMLs on cross-sectional scanning electron microscopy (SEM) images automatically. Findings – The increase of the IML thickness is lower in the case of HAST ageing compared to other methods. The thickness increment of the Cu6Sn5 layer was higher for IR and lower for VP soldering; the Cu3Sn layer cannot be inspected even after 2,000 hours of HAST ageing. The results of shear strength measurements show better reliability for VP soldered joints. Practical implications – The developed image processing method is applicable to obtain quantitative results about the IMLs in an effective fast way. Originality/value – There is a lack of information in the literature regarding the reliability comparison of solder joints formed with VP and conventional reflow processes. Thus, we performed research about the lifetime of solder joints formed with VP and IR reflow method.

Effect of surface treatment to inserted ring on Al-Fe bonding layer of aluminium piston with reinforced cast iron ring

In order to improve the bonding strength between piston alloys and cast iron ring of aluminum piston with reinforced cast iron ring, the different methods of the surface treatments (shot blasting and sand blasting) to the cast iron ring are experimented. The optical micrograph shows that an intermetallic layer and a ligulate shaped structure are formed between piston alloys and cast iron base ring. After sand blasting treatment, the ring surface is non-metal shiny, matte-like and has no obvious pits. The intermetallic layer thickness formed between piston alloys and cast iron is thinner and more equally distributed after sand blasting to the ring. The content of the graphite distributed the interfacial zone after the shot blasting treatment is little. With the increase of time by sand blasting, the hardness starts to slightly descend. The bonding strength of the sample by sand blasting is obviously higher than that by shot blasting and increases from 9.32 MPa to 19.53 MPa.

Rapid intermetallic growth under high strain rate deformation during high power ultrasonic spot welding of aluminium to steel

Abstract High power ultrasonic spot welding is an alternative manufacturing process which recently has been developed for joining automotive bodies. This technique is a very low energy process, forming effective welds in less than a second particularly for difficult dissimilar material combinations such as aluminium to steel joint. However, in dissimilar joint the interdiffusion and thus intermetallic formation was accelerated due to high strain rate dynamic deformation in ultrasonic spot welding which deteriorates mechanical performance. The interfacial reaction between aluminium 6111-T4 and DC04 uncoated steel has been investigated as a function of welding time. For the optimum welding time of 1.5 s under a 1.4 kN axial pressure, the intermetallic layer thickness could have reached ∼1.0 μm. Intermetallic islands were seen to nucleate across the microbonds at the interface within short welding times which spread and grow rapidly forming a continuous layer which mainly contains FeAl3 and Fe2Al5 phases. The interfacial reaction occurred in solid state even for a long welding time. Modelling was carried out with the aim of showing that the rate of interfacial reaction was over 6 times greater than the rate observed in diffusion couple using rate constants achieved from the static heat treatment condition. This confirms that deformation-induced vacancies during the thermomechanical welding process accelerates formation of intermetallic layer at the interface.

Properties and Growth Rate of Intermetallic Al-Fe through Hot Dipped Aluminizing

Hot dipped aluminizing is the one of the most famous and effective method of the surface protection. The growth behavior in the intermetallic layer by introducing a different dipping time and various of molten aluminium temperature had been detail investigated. The result showed that the top portion of the coated steel substrate is compose of a thin layer of α-Al2O3, followed by thicker Aluminium pure layer, thinner layer of FeAl3 , and then a much thicker of Fe2Al5. The inter-metallic layer is ‘thick’ and exhibits a finger-like growth into the steel. The thickness of Al-Fe intermetallic layer on the steel base is increased with the increasing of hot dipping temperature and time. The micro hardness testing result shown that increasing of the aluminizing temperature was increased the hardness of the intermetallic layer.

Improving of interfacial microstructure of Ti/Al joint during GTA welding by adopting pulsed current

Butt welding of titanium alloy TA15 to aluminum alloy Al2024 dissimilar lightweight metals was conducted using gas tungsten arc welding. Pulsed current was adopted in the welding process. Influence of pulsed current on morphologies and microstructure of Ti-Al intermetallics near the Ti/Al interface was investigated. Microstructure characteristics and phase constitution of weld zone near the Ti/Al interface were analyzed. In top surface and upper region of the joint, Ti base metal was partially melted, and continuous intermetallic layers with Ti3Al, TiAl, and TiAl3 were formed in the fusion zone. In middle and bottom regions of the joint, Ti base metal was not melted and a thin TiAl3 layer was formed near the Ti/Al-brazed interface. Most of the Ti-Al intermetallics formed into discrete TiAl3 precipitations in the weld metal in upper and middle regions of the joint. No precipitation was observed in bottom region of the joint. Thickness of continuous Ti-Al intermetallic layers in the fusion zone was controlled at a low degree by adopting pulsed current in the welding. Crack sensitivity of weld zone near the Ti/Al interface was decreased.

Ultrafine-Grain and Isotropic Cu/SAC305/Cu Solder Interconnects Fabricated by High-Intensity Ultrasound-Assisted Solidification

With the miniaturization of portable electronic devices, the size of solder joint interconnects is decreasing to micrometer levels. These joints possess only several or even one or two grains, resulting in anisotropy and failure issues. Direct ultrasound-assisted solidification of Cu/SAC305/Cu interconnects for grain refinement and fabrication of isotropic solder joints is presented herein. These joints consist of many β-Sn grains. The average cross-sectional area of the Sn-rich phase is significantly reduced by up to 99% when compared with conventional as-reflowed samples. The ultrasonic power density exhibits a threshold value for affecting the microstructures. Below 200 W cm−2, the β-Sn grains were refined and had circular shape. The Ag3Sn phase grew in a manner similar to branched coral to sizes reaching 30 μm, or as rods aggregated together with Cu6Sn5 tube fragments. Above 200 W cm−2, the microstructures were coarsened and Ag3Sn had plate-like shape. The thickness of Cu6Sn5 intermetallic layers at the Cu/solder interfaces was reduced by more than 26%. The relationships among the ultrasonic power, nucleation rate, local temperature drop, and pressure were identified. At the highest power density of 267 W cm−2, the nucleation rate was about 4.05 × 1014 m−3 s−1, the local temperature drop was 248 K, and the local pressure was on the order of several GPa.

Shear Strength of Eutectic Sn-Bi Lead-Free Solders After Corrosion Testing and Thermal Aging

Low-cost manufacturing in the electronics industry is becoming more demanding, particularly in the production of consumer electronics. Such manufacturing processes require reliable and low-cost lead-free solders. Among the low temperature lead-free solders, eutectic Sn-Bi solder has attracted a great deal of interest since it offers good reliability comparable to that of Sn-Pb solders. In this paper, the shear strength of eutectic 42Sn-58Bi (wt.%) lead-free solder was studied using combinations of environmental tests including thermal aging at 100 °C, salt spray test, and a sequential combination of these tests. Microstructural studies on samples were performed at different time intervals of testing. To study the effect of salt spray and thermal aging on the mechanical reliability, shear testing was performed on the samples. Failure analysis including fractography on samples was conducted at different time intervals using a scanning electron microscope. Considerable corrosion was observed after the salt spray test. This was found to have a significant effect on the shear strength of the solder joints. Additionally, thermal aging was found to cause coarsening and to increase the thickness of intermetallic layers. This was also found to adversely affect the shear strength. The combination test was found to have the most significant effect, as the lowest shear strengths were seen after this testing.

5056 Aluminum Alloy and Coated Steel Overlapped Fusion Welding-brazing by Laser with Preset Filler Powder

In view of the technical difficulties of aluminum/steel welding, CO2 laser fusion welding-brazing is used to produce lap joint between 5056 aluminum alloy and ST04Z galvanized steel with filler powder. Weld appearance, microstructure and mechanical properties of welding joint are studied. The results show that high quality welding joint can be obtained by using the appropriate welding parameters with preset filler powder. The intermediate layer thickness is less 10 μm, and acicular intermetallic compound is not separated out to melted aluminum alloy. There are two rich Zn zones during fusion joint, which are located at melted edge and welding-brazing root. Si,Zn,Mn and Mg elements constitute compounds or solid solution with Al and Fe elements, which rigid intermetallic compounds are stopped to generate by restraining Al and Fe elements direct contact. Tensile specimen fracture mainly in the aluminum alloy heat affected zone or welds, and Welds fracture surfaces are all at the side of the aluminum melting area. The average mechanical resistance of 190 N/mm is obtained, about 85.2% of the base metal of 5056 alloy. By using this laser fusion welding-brazing method and filler special powder,the thickness of intermetallic compounds layer can be decreased and the fusion welding-brazing joints with excellent mechanical properties can be obtained.

Dependence of electromigration damage on Sn grain orientation in Sn–Ag–Cu solder joints

The relationship between the “polarity effect” of electromigration on interfacial intermetallic growth and the Sn grain orientation was investigated in Sn-Ag-Cu solder joints. The growth of the interfacial intermetallic compound was found to depend strongly on the Sn grain orientation. When the c-axes of the Sn grains were closely aligned to the current flow direction, a severe polarity effect was observed in which the anode interface was covered with a thick layer of Cu-Sn intermetallic while the intermetallic layer at the cathode interface was almost depleted. If the c-axes of the Sn grains were rotated away from the current direction, the polarity effect became less pronounced. When the c-axis was perpendicular to the current direction, the polarity effect essentially disappeared. The difference in the intermetallic layer thickness between the anode and the cathode, Δd, followed a parabolic function of the cosine of the angle, α, between the c-axis and the current direction. A kinetic model based on the highly anisotropic diffusion behavior of Cu in Sn was presented to explain the relationship between the electromigration polarity effect and Sn-grain orientation. The model showed good agreement with the experimental data.

Hot-Dip Aluminizing of Low Carbon Steel Using Al-7Si-2Cu Alloy Baths

Hot-dip aluminizing of low carbon steel was done in molten Al-7Si-2Cu bath at 690°C for dipping time ranging from 300 to 2400 seconds. Characterization of the intermetallics layer was done by using scanning electron microscope with energy dispersive spectroscopy. Four intermetallic phases, τ5-Al7Fe2Si, θ-FeAl3, η-Fe2Al5, and τ1-Al2Fe3Si3, were identified in the reaction layer. τ5- Al7Fe2Si phase was observed adjacent to aluminum-silicon topcoat, θ-FeAl3 between τ5 and η-Fe2Al5, η-Fe2Al5 adjacent to base material, and τ1-Al2Fe3Si3 precipitates within Fe2Al5 layer. The average thickness of Fe2Al5 layer increased linearly with square root of dipping time, while for the rest of the layers such relationship was not observed. The tongue-like morphology of Fe2Al5 layer was more pronounced at higher dipping time. Overall intermetallic layer thickness was following parabolic relationship with dipping time.

Effect of intermetallic compounds on heat resistance of hot roll bonded titanium alloy–stainless steel transition joint

The effect of intermetallic compounds on the heat resistance of transition joint was investigated. The experiment of post-weld heat treatment for the hot roll bonded titanium alloy–stainless steel joint using nickels interlayer was carried out, and the interface microstructure evolution due to heat treatment was presented. There was not found significant interdiffusion at stainless steel/nickel interface, when the specimens were heat treated in the temperature range of 600–800 °C for 10 and 30 min, while micro-cracks occurred at the stainless steel/nickel interface heat treated at 700 °C for 30 min. The thickness of intermetallic layers at nickel/titanium alloy interface increased at 600 °C, and micro-cracks occurred at 700 and 800 °C. The micro-cracks occurred between intermetallic layers or between intermetallic layer and nickel interlayer as well. The tensile strength of the transition joint decreased with the increase of heat treatment temperature or holding time.