Abstract
In this work, the reactive wetting and infiltration behaviors of a newly designed Sn-V binary alloy were comprehensively explored on porous graphite for the first time. It was discovered that 0.5 wt.% addition of V can obviously improve the wettability of liquid Sn on porous graphite and the nominal V contents in Sn-V binary alloys has minor effects on the apparent contact angles wetted at 950 °C. Moreover, the V-containing Sn-V alloys were initiated to spread on porous graphite at ~650 °C and reached a quasi-equilibrium state at ~900 °C. Spreading kinetics of Sn-3V alloy on porous graphite well fitted in the classic product reaction controlled (PRC) model. However, our microstructural characterization demonstrated that, besides vanadium carbide formation, the adsorption of V element at the wetting three-phase contact line spontaneously contributed to the reactive spreading and infiltrating of Sn-V alloys on porous graphite. Meanwhile, the formation of continuous vanadium carbides could completely block the infiltration of Sn-V active solder alloy in porous graphite. Affected by the growth kinetics of vanadium carbides, the infiltration depth of Sn-V alloys in porous graphite decreased at increased isothermal wetting temperatures. This work is believed to provide implicative notions on the fabrication of graphite related materials and devices using novel V-containing bonding alloys.
Highlights
Graphite has a high thermal conductivity, low coefficient of thermal expansion (CTE), and superior wear resistance that makes it widely applied as enhancing particles in metal matrix composites (MMCs) and as a protective coating
When V contents of Sn-V alloys were further increased to 5 and 7 wt.%, flat platforms became more visible on the top of solidified Sn-5/7V alloys, as shown in Figure 2e,f, where the spreading area of Sn-7V alloy decreased significantly
chemical vapour deposition (CVD) diamond on above thewhich wettability alloythan on porous and polycrystalline diamondBased substrate can be analysis, the difference in the wettability of alloy on porous graphite and polycrystalline attributed to the difference in patterns of mass transfer: the vertical infiltration process of Sn-V CVD
Summary
Graphite has a high thermal conductivity, low coefficient of thermal expansion (CTE), and superior wear resistance that makes it widely applied as enhancing particles in metal matrix composites (MMCs) and as a protective coating. Park et al stated that, given a certain mismatch of CTEs, the residual thermal stress in ceramics/metals joints is directly related to the brazing temperature [7] These results well agreed with Zhong et al.’s work (2009) that the cracks or fracture mainly occurred through the interfacial beam between the graphite and filler alloys [8]. Considering the thermal residual stress is directly related to brazing temperature, Yu et al [13] and Tsao et al [14] applied active filler alloys of lower fusibility to braze Al to graphite or Al-graphite composite, respectively; ultrasonic vibration or external pressure was needed to assist the wetting of bonding metals on graphite. At three-phase contact line wetted after different thermal histories
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