Direct Observation of Wetting and Spreading of Molten Aluminum on TiB2 in the Presence of a Molten Flux from the Aluminum Melting Point up to 1033 K (760 °C)

Abstract

The wetting and spreading of molten aluminum on TiB 2 substrates between the aluminum melting point and 1033 K (760°C) was investigated in the presence of different types of fluxes. The wetting and spreading behavior is observed to depend on the flux, its melting point, its chemistry, and its ability to dissolve alumina. When the flux melting point is higher than the melting point of aluminum, the molten aluminum takes on an initial spherical shape as a result of the thin alumina layer on its surface. After the flux is melted, it dissolves the alumina layer on the liquid aluminum surface causing the aluminum to wet and spread on the substrate. When the flux melts before the aluminum, the alumina layer on the solid aluminum surface is dissolved into the flux. In this case, the aluminum surface in contact with the molten flux is alumina layer free. Thus, the aluminum does not take a spherical shape after melting; it rapidly melts, wets, and spreads on the substrate. The use of a flux allows the wetting behavior of aluminum on TiB 2 to be observed at lower temperatures than previously reported.

Ultrasonic-Assisted Synthesis of Surface-Clean TiB2 Nanoparticles and Their Improved Dispersion and Capture in Al-Matrix Nanocomposites

“…Nanoscaled metal borides exhibit a wide range of properties, including conduction, luminescence, thermoelectricity, magnetism, and ultrahardness, among others, that makes them interesting in the fields of refractory conductive ceramics, superconductors, and hard materials . In this context, titanium diboride (TiB 2 ) NPs are an excellent candidate as the reinforcing element in MMNCs because TiB 2 (i) is thermodynamically stable in liquid Al; (ii) has a low interfacial energy (and thus, good wettability) with Al, , which ensures effective NP incorporation in the melt; and (iii) has a Hamaker constant close to that of the liquid Al, which would promote NP capture by Brownian motion during metal front solidification . However, the commercially available nanosized TiB 2 has a surface carbon-coating inherent to the arc-plasma synthetic process, which promotes the oxidation reactions and hinders NP incorporation into the metal melt, making it not useful for reinforcing material in solidification-processing of MMNCs.…”

Wettability of Low Weight Borides by Commercial Aluminum Alloys − A Basis for Metal Matrix Composite Fabrication

“…To ensure wetting even at temperatures close to the melting point of aluminum (660 °C), different types of fluxes can be used as wetting agents. It was possible to reach contact angles about 9° for TiB 2 in argon atmosphere after 30 min by using fluxes . All investigators assert that there was no reaction between aluminum and TiB 2 , although a decrease of the contact angle during testing occurred, what could have been due to the reaction between the aluminum and oxides (TiO 2 and B 2 O 3 ) usually present at the TiB 2 substrate surface …”

Developing Sc and Zr containing Al-B C metal matrix composites for high temperature applications /

“…Ti was supposed to partially replace the reactions between Al and B4C and to introduce a new reaction product of TiB2 enclosing the entire B4C particles [25,152,160]. The Al was able to strongly wet TiB2 even at temperature below 1000 °C [161,162]. This process obviously enhanced the wettability of Al on the ceramic reinforcements.…”