Low-temperature partial transient liquid phase diffusion bonding of Al/Mg2Si metal matrix composite to AZ91D using Al-based interlayer

Partial transient liquid phase diffusion bonding of an aluminium metal matrix composite (Al/Mg2Si) to magnesium alloy (AZ91D) was performed using two heating rates. The influence of different heating rates on the microstructure, microhardness and shear strength has been studied. With a decrease in heating rate from 20 to 2 °C/min, the Mg content in the bond line decreased and the microstructure was altered. The composition and microstructure of the joined areas were examined by X-ray diffraction (XRD) and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (EDS). It was found that a heating rate of 2 °C/min resulted in an increasing in the shear strength of the joints. The kinetics of the bonding process accelerated due to the increase of solute diffusivity through grain boundaries of the metal matrix composite. Results suggest that Mg and Si contained in the interlayer favours the partial disruption of oxide films, facilitating the bonding process

Diffusion Brazing of Ti-6Al-4V and Stainless Steel 316L Using AgCuZn Filler Metal

In the present study, vacuum brazing was applied to join Ti-6Al-4V and stainless steel using AgCuZn filler metal. The bonds were characterized by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction analysis. Mechanical strengths of the joints were evaluated by the shear test and microhardness. It has been shown that shear strength decreased with increasing the brazing temperature and time. The wettability of the filler alloy was increased by enhancing the wetting test temperature. By increasing the brazing temperature various intermetallic compounds were formed in the bond area. These intermetallic compounds were mainly a combination of CuTi and Fe-Cu-Ti. The shear test results verified the influence of the bonding temperature on the strength of the joints based on the formation of different intermetallics in the bond zone. The fracture analysis also revealed different fracture footpath and morphology for different brazing temperatures

Partial transient liquid phase diffusion bonding of zircaloy-4 to stabilized austenitic stainless steel 321 using titanium interlayer

In this study, an innovative method was applied for bonding Zircaloy-4 to stabilized austenitic stainless steel 321 using an active titanium interlayer. Specimens were joined by partial transient liquid phase diffusion bonding method in a vacuum furnace at different temperatures under 1 MPa dynamic pressure of contact. The influence of different bonding temperatures on the microstructure, microindentation hardness, joint strength, and interlayer thickness has been studied. Additionally, a simple numerical model was developed to predict the evolution of interlayer during partial transient liquid phase diffusion bonding. Diffusion of Fe, Cr, Ni, and Zr has been investigated by scanning electron microscopy examinations and energy dispersive spectroscopy elemental analyses. Results showed that control of heating and cooling rate and 20 min soaking at 1223 K produces a perfect joint. However, solid state diffusion of the melting point depressant elements into the joint metal causes the solid/liquid interface to advance until the joint is solidified. The tensile strength values of all bonded specimens were found around 480–670 MPa. Energy dispersive spectroscopy studies indicated that the melting occurred along the interface of bonded specimens as a result of transfer of atoms between the interlayer and the matrix during bonding. The evolution of interlayer film thickness indicates a good agreement between the calculation and experimental measurement. This technique provides a reliable method of bonding zirconium alloy to stainless steel

Corrosion behavior of heat treated nickel-aluminium bronze alloy in artificial seawater

The effect of microstructure of nickel-aluminum bronze alloy (NAB) on the corrosion behavior in artificial seawater is studied using linear polarization, impedance and electrochemical noise tests. The alloy was heat treated in different heating cycles including quenching, normalizing and annealing. Microstructure of the specimens was characterized before and after heat treatment by optical microscopy and scanning electron microscopy. Results showed that the value of pearlite phase in the normalized alloy is much more than other specimens, leading to higher corrosion resistance. Polarization test showed that starting point of passivation in the polarization of the normalized alloy is lower than other specimens. The dissolution of Mn and Fe rich phases increased the Mn and Fe contents in solid solution, and this enhanced the passivation power of the surface of the alloy. The effect of the alloying elements was seen by a lower corrosion potential and an inflexion at around 280 mV (SCE) in the polarization curve, indicating the preferential dissolution of some elements beyond that potential. The polarization curve showed that the anodic polarization behavior of the alloy in the solution was essentially controlled by the intermetallic phases, mainly containing Cu. Two types of corrosion, pitting and selective corrosion, were observed in the specimens after being exposed to artificial seawater

Transient liquid phase diffusion bonding of stainless steel 304 using copper and aluminium filler interlayers

Stainless steel 304 was successfully joined by transient liquid phase diffusion bonding. The bonding process was carried out in a vacuum furnace at various temperatures for various diffusion times, using pure copper interlayer. The joints were studied with optical and scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and corrosion test. The diffusion of the main elements from the interlayers into the base metal at the bonding temperatures was the main controlling factor pertaining to the microstractural evolution of the joint interface. In order to determine the corrosion resistance of the joints, Tafel test was conducted in 3.5% NaCl solution. The presence of eutectoid γFe+ eutectic Cu + Cr was detected at the interface of the joints bonded with copper. The joints related to stainless steel-copper developed crevice corrosion due to galvanic couple between the stainless steel and copper. Pitting was also occurred due to intergranular corrosion on the copper surface

Transient liquid phase diffusion bonding of stainless steel 304 using copper and aluminium filler interlayers

Stainless steel 304 was successfully joined by transient liquid phase diffusion bonding. The bonding process was carried out in a vacuum furnace at various temperatures for various diffusion times, using pure copper interlayer. The joints were studied with optical and scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and corrosion test. The diffusion of the main elements from the interlayers into the base metal at the bonding temperatures was the main controlling factor pertaining to the microstractural evolution of the joint interface. In order to determine the corrosion resistance of the joints, Tafel test was conducted in 3.5% NaCl solution. The presence of eutectoid γFe+ eutectic Cu + Cr was detected at the interface of the joints bonded with copper. The joints related to stainless steel-copper developed crevice corrosion due to galvanic couple between the stainless steel and copper. Pitting was also occurred due to intergranular corrosion on the copper surface