Interface Engineering and Direct Observation of Strengthening Behavior in Field‐Sintered Boron Nitride Nanotube–Magnesium Alloy Composite

Abstract

Boron Nitride Nanotube (BNNT) is integrated in AZ31 magnesium alloy by field-assisted powder metallurgy route. A mat of BNNT is sputter-coated with pure Mg and then sandwiched between AZ31 alloy powders. This layered composite is consolidated by spark plasma sintering. A high processing pressure of 400 MPa aids in intimate alloy-nanotube adhesion due to localized deformation. Thermal diffusion between AZ31 and BNNT (at 400°C sintering temperature) results in the formation of Mg 3 N 2 and AlN nano-phases at the interface. Due to ultrafast Joule heating during SPS, the reactions are kinetically controlled and only trace amounts of products are formed without compromising the characteristics of the nanotubes. The interphases aid in reactive-bonding between AZ31 and BNNT, which is essential for load-bearing applications. In-situ double cantilever loading of the composite inside the scanning electron microscope shows that the nanotubes bridge, resist, and delay crack propagation. These findings demonstrate the promise of thermally-stable BNNTs as reinforcement for engineering lightweight Mg-based structural composites.

Assessment and Non-Destructive Evaluation of the Influence of Residual Solvent on a Two-Part Epoxy-Based Adhesive Using Ultrasonics

“…Destructive testing, which involves using lab-type instrumentation that requires a specific sample preparation and geometry, is mainly performed to characterize the mechanical properties of materials [14][15][16][17][18][19][20][21]. It has also been used to characterize the curing kinetics of polymeric materials.…”

In Situ Investigation of Deformation Mechanisms Induced by Boron Nitride Nanotubes and Nanointerphases in Ti–6Al–4V Alloy

“…[ 14,15 ] This makes BNNT a highly suitable candidate for engineering metal matrix composites as metal manufacturing processes typically involve exposure to elevated temperatures. Fabrication of BNNT‐reinforced aluminum and magnesium composites has been reported via magnetron sputtering, [ 16 ] ion implantation, [ 17 ] powder metallurgy, [ 18–23 ] solidification, [ 24,25 ] mechanical working, [ 26,27 ] and thermal spray [ 28 ] routes. These studies have demonstrated promising improvements in elastic modulus, [ 22,28 ] hardness, [ 18–21,28 ] and strength [ 18,19,21,22,24,26,27 ] of metal matrices due to BNNT addition.…”

Boron Nitride Nanotube–Reinforced Titanium Composite with Controlled Interfacial Reactions by Spark Plasma Sintering

“…[16][17][18][19][20][21][22] In addition to the proven thermal and oxidation stability of BNNTs (up to 900 C in air), these nanostructures have shown extensive damage tolerance at temperatures of 250-500 C. [18,19,23,24] The addition of BNNTs as reinforcing nanoparticles in low-melting-point metal matrices such as aluminum and magnesium has resulted in composites with competitive moduli, fracture strength, and unique deformation mechanisms under tension and compression. [5,9,10,21,[25][26][27][28][29] A key challenge in the integration of BNNTs to Ti matrices lies in control over the interfacial interactions between the nanotube and the matrix during sintering. A thin reaction layer (%5-10 nm) [30] will aid in increasing bonding strengths and promote the effective transfer of stresses.…”

“…[ 18,19,23,24 ] The addition of BNNTs as reinforcing nanoparticles in low‐melting‐point metal matrices such as aluminum and magnesium has resulted in composites with competitive moduli, fracture strength, and unique deformation mechanisms under tension and compression. [ 5,9,10,21,25–29 ]…”