Microstructural Evolution And Mechanical Properties of FCAW Joints In 9% Ni Steel Prepared With Two Types of Ni-Based Weld Metals

The microstructural and mechanical evaluation of 9% Ni steel with Flux-Cored Arc Welding was performed with two different Ni-based weld metals: Inconel 625 and Hastelloy 609. Weld metals showed the microstructural change depending on the temperature gradient and crystal growth rate for each region during the cooling after welding. At the bottom of the weld metal, which is rapidly cooled in contact with the cold base metal, a cellular/planar growth was exhibited due to a large temperature gradient and low crystal growth rate. While, columnar dendrites were exhibited in the central region cooled relatively slowly and precipitates were observed in the interdendritic region. In the low-temperature toughness test, the absorbed impact energies were 89 and 55 J for Inconel 625 and Hastelloy 609, respectively. When Inconel 625 is used as the weld metal compared to Hastelloy 609, the high content of the γ stabilizer and martensite start temperature decreasing elements leads to the formation of a thicker γ-phase layer and thinner martensite layer in the transition region. In addition, high content of these elements suppresses the martensite transformation and maintains the stability of the weld joint interface even at low temperatures, resulting in the higher absorbed impact energy.

Effect of FW conditions on mechanical and microstructural characteristic of AA6061/SiC/Graphite hybrid composites joint by empirical relationship

Friction welded AA6061 matrix hybrid composite joints were investigated to understand the process effect on the metallurgical properties with the aid of empirical relationships. SiC of 10 % with the standard particle size of 25 µm and 5 % graphite with the particle size of 30 µm were added into the AA6061 matrix. The investigation has 20 sets of experiments as per the matrix designed. Each process condition, namely rotation speed (N), upset load (F), and upset time (T), as well as their impact on joint properties, were investigated individually, with the estimated tensile strength correlated to their corresponding metallographic properties. The observation of this study concludes that the disparity in grain size is mainly affected by the availability of heat sources and the plasticized material during the friction stage and it is highly influenced by rotation speed. Furthermore, the lower level parameters produce the defective joint while the higher-level parameters are attributed to ejecting the extensive amount of hot material from the joint interface. Finer reduction in grain size of 1.5 µm and ample plasticized material consolidation at the optimized welding conditions of 1600 rpm rotation speed, 3.5 kN upset load, and 4 s upset time were attributed to achieving the maximum tensile strength of 167 MPa.

InP based high speed p-i-n photodetector monolithic integrated with MQW semiconductor optical amplifier

We demonstrate an InP based high speed p-i-n photodetector monolithic integrated with MQW semiconductor optical amplifier. A butt-joint scheme is adopted to connect the SOA and evanescent wave photodetector. The chip allows separate design for SOA and PD and needs only two MOCVD growth steps, which promises high yield and reduced manufacturing cost. The fabricated 5×20 μm2 PD shows a low dark current of 300 pA at -3V. The optical gain bandwidth of the SOA is 50nm, covering whole c-band. Gain ripple of SOA is 0.5dB, indicating that internal parasitic reflectivity is negligible. For integrated chip with 500μm SOA, the on-chip gain and total chip responsivity at 1545 nm can reach 12.8 dB and 7.8 A/W respectively. Insertion loss of the butt-joint interface is estimated to be 1.05 dB/interface. Small signal 3dB bandwidth at -5V of the integrated chip reaches 20GHz, showing no deterioration compared to discrete PD.

Research on the Physical Characteristics of Hot-Pressed Sintering Preparing Self-Fluxing Filler by X-Ray Diffraction

In this paper, Al-12Si self-fluxing filler metal ring was prepared with Al-12Si alloying powders and KAlF4 flux by hot pressed sintering (HPS) method. The microstructure and mechanical properties of the brazing alloy and the brazed 3003 aluminum alloy joint were investigated. The results showed that Al-12Si self-fluxing filler metal ring could be successfully obtained by HPS at 470°C using a pressure of 300MPa. The prepared filler metal ring was dense and defect-free and the microstructure was mainly composed of Si phase with KAlF4 flux grain uniformly distributed in the Al matrix. The 3003 aluminum alloy joint interface brazed by the prepared filler metal was also well bonded and no pore and defect was found. A quite high joint strength of 75MPa was obtained which is equal to the strength of joint brazed using commercial Al-Si self-fluxing wires prepared by hot extrude method. The results revealed that the filler metal rings fabricated by HPS process had great potentiality in brazing of aluminum alloy especially for the Al-Al pipes joining due to its high joint strength, low cost and the convenience for industrial application.

Ultrasonic-Assisted Brazing of Titanium Joints Using Al-Si Based Fillers: Numerical and Experimental Process Design

The ultrasonic-assisted brazing process was studied both numerically and experimentally. The ultrasonic brazing system was modeled by considering the actual brazing conditions. The numerical model showed the distribution of acoustic pressure within the filler and its variations according to the gap distance at different brazing temperatures. In the experimental part, brazing joints were studied and evaluated under multiple conditions and parameters. Although either the initial compression load or the ultrasonic vibration (USV) can initiate the interaction at the interface, the combined effect of both helped to produce joints of a higher quality with a relatively short brazing time, which can be further optimized in terms of their mechanical strength. The effect of the Si content on the joint interface, and the effect of the brazing conditions on the microstructures were studied and discussed.

Experimental and Numerical Investigation of Load Failure at the Interface Joint of Repaired Potholes Using Hot Mix Asphalt with Steel Fiber Additive

The maintenance of potholes is a long-standing problem. Previous studies focused on pothole patching materials and methods but not on bonding at the interface joint. In this study, the influence of the patching shape and depth on the bonding at the interface joint using two patching materials: hot mix asphalt (HMA) and hot mix asphalt containing 5% (by volume) steel fiber (HMA+) was investigated. Slabs with circular and square potholes in the middle with different depths (35, 50 and 70 mm) were prepared. The two shapes of potholes were patched with two patching materials: HMA and HMA+, at different depths. The slabs were tested after patching using a rigid steel frame. The experimental results were compared with those obtained from finite element analysis using the ABAQUS software, applying the same model of slabs with the same dimensions and properties of the materials used. The results indicated that the bonding at joint interface for circular-patched potholes slightly improved using HMA+ and this was independent of patching depth. As for the square-patched potholes, the bonding at the interface joint was better than for the circular-patched ones; the bonding increased with increasing depth. Using HMA+ for patching the square-patched potholes, the bonding at the interface joint slightly increased, only for the 3.5 cm depth.

An Investigation of the Effect of Intermetallic Compounds on the Mechanical and Electrical Properties of Friction Stir Welded Al and Cu Busbar for Battery Pack Applications

Aluminium and copper (Al-Cu) busbar is widely used as a core component in Lithium-Ion (Li-ion) batteries. The Al-Cu busbar is challenging to fabricate with the traditional welding processes because of its high thermal conductivity. In the present study, the Al-Cu busbar is fabricated using the friction stir welding method. The effect of temperature and vibration generated during the welding process on the formation of intermetallic compounds (IMCs) is studied by using the effective formation model and found that Al2Cu is the first to form at the interface. The IMC formation at the joint interface had both detrimental (Al-rich IMC) and beneficial (Cu-rich IMC) effects. The presence of detrimental IMCs affects the joint strength of about 36 % as compared to the sample with the highest tensile load. The surface electrical conductivity is measured by using a Gaussian profile method and found in the range of 0.94 – 5.37 μ Ω·mm. The welded samples with the presence of Al2Cu3 and Al4Cu9 IMC at the interface are found to have higher electrical conductivity. Interestingly, the sample with a higher tensile load had observed higher electrical conductivity due to the formation of Cu-rich IMC, i.e., Al4Cu9.

Effect of Interfacial Intermetallic Compounds Morphology on Mechanical Properties of Laser Brazing of Aluminum to Steel

The paper provides experimental details of the welding and specific examples of welding aluminum welding battery cans and conductive tabs for battery pack manufacture. In this study, we provide experimental details of a process for joining dissimilar materials used in sealing battery parts. A laser brazing technique was used for the lap joining of aluminum alloy and a deep drawing quality stainless steel, with an Al-Si filler metal. These materials are commonly used in battery applications, as materials for the cap plate, tab plate and can. The relationships among the width of the brazed zone, formation of intermetallic compounds (IMCs), shape of the joint interface, and joint strength were systematically investigated with respect to the laser power and filler wire feeding rate. When a low and medium laser power (1.2-2.0 kW) was applied, the joint strength was very low, and fracture occurred across the band-shaped IMC layer. With a further increase in the applied laser power (2.2-2.8 kW), a new needle-like IMC composed of Al13Fe5 with a monoclinic crystal structure was formed, and it penetrated the brazed zone. In addition, the width of the brazed zone increased due to the partial melting of the aluminum. The joint efficiency under a high laser power condition was 70% compared to that of the base material. Fractures occurred alternately along the needle-shaped IMC and filler metal zone. Since the fracture propagated along the needle-like IMCs inside the brazed zone, the peak load was higher than that of the band-shaped IMCs.