Abstract
The formation of interfacial reaction layers was investigated in an α-Al2O3/430 stainless steel (SS430) joint brazed using a Cu-7Al-3.5Zr active brazing alloy. Brazing was conducted at above its eutectic temperature of 945 °C and below liquidus 1045 °C, where liquid and solid phases of the brazing alloys coexists. At 1000 °C, the liquid phase of the brazing alloy was wet onto the α-Al2O3 surface. Zr in the liquid phase reduced α-Al2O3 to form a continuous ZrO2 layer. As the dwell time increased, Zr in the liquid phases near α-Al2O3 interface was used up to thicken the reaction layers. The growth kinetics of the layer obeys the parabolic rate law with a rate constant of 9.25 × 10−6 cm·s−1/2. It was observed that a number of low yield strength Cu-rich particles were dispersed over the reaction layer, which can release the residual stress of the joint resulting in reduction of crack occurrence.
Highlights
Heterogeneous metal-ceramic joints have been found in a number of applications such as electronic devices, automobiles, and high-temperature batteries [1,2,3,4,5,6,7]
Because a brazed joint using this type of alloy provides a high bonding strength and good oxidation resistance at high temperatures of up to 600 ◦ C [14,15], the alloy has been applied to a wide variety of energy and automotive applications under high-temperature environments
The results indicated that the conditions and represented with error bars
Summary
Heterogeneous metal-ceramic joints have been found in a number of applications such as electronic devices, automobiles, and high-temperature batteries [1,2,3,4,5,6,7]. Because a brazed joint using this type of alloy provides a high bonding strength and good oxidation resistance at high temperatures of up to 600 ◦ C [14,15], the alloy has been applied to a wide variety of energy and automotive applications under high-temperature environments. In developing a stable high-temperature brazing alloy resistant to liquid Na, previous studies have suggested adopting Cu-7Al-xTi and Cu-7Al-xZr (x = 2.5, 3.5 and 4.5) alloys, which consist of Metals 2018, 8, 990; doi:10.3390/met8120990 www.mdpi.com/journal/metals. Where theCu-7Al-xZr liquid and solid phases of brazing alloy coexisted, crack-free joints were observed jointsC, using only alloys. The majorityofofthe studies havealloy beenand conducted above the liquidus temperature to improve the wettability wettability brazing chemical reaction.
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