Aluminium Matrix Hybrid Composites — big words, big on potential
// Pranav Krishnan
Power Professor couple Siddhartha Das and Karabi Das, partners in crime at the Department of Metallurgical and Materials Engineering, IIT Kharagpur, have been at it again.
In conjunction with their PhD. student, Jamuna Sethi, the trio recently prepared a thermally stable Aluminium matrix hybrid composite, that paves the way for usage in different structural applications, such as in aerospace, antennas and electronic packaging.
A metal matrix composite is a continuous metal matrix, with a reinforcing material dispersed within it. More than 3 materials in it, and it’s a hybrid MMC.
Aluminium is prized for engineering usage, thanks to being lightweight yet extremely strong. While it has a strength to weight ratio that can match steel, the relentless level of performance under high temperatures and pressure, like aerospace applications demand, comes into question.
Here’s where matrix composites come into the picture. By reinforcing the Aluminium with negative thermal expansion (NTE) materials, the coefficient of thermal expansion of the metal is effectively lowered, making it more thermally stable. The flipside is that the NTE material can deteriorate some valuable properties like strength, ductility and thermal conductivity — manipulating materials is a delicate balance.
To mitigate this, the researchers reinforced the Al matrix with more than one reinforcement, namely Yttrium Tungstate (Y2W3O12) and Aluminium Nitride (AlN) particles, developing a new AHMC with a low CTE value and high strength.
J. Sethi et al. / Journal of Alloys and Compounds 774 (2019)The Yttrium Tungstate was synthesized in-house, and the material processing techniques — solid state powder metallurgy to fabricate, high energy Fritsch Pulverisette-4 ball milling, compaction and sintering — carried out in the couple’s laboratory here in campus.
Eight different composites, of varying composition were made — broadly divided into four rich in yttrium tungstate, and four rich in AlN. X-Ray Diffraction performed on the materials to obtain their properties, gleaned some interesting results:
- The hardness of the composites was significantly harder than pure Al
- Compressive strength and thermal conductivity of yttrium tungstate rich composites increased significantly, thanks to the addition of the second component, AlN, vindicating the decision to use it
Yttrium Tungstate-rich composites
AlN-rich compositesThe black and grey regions in the micro-graphs correspond to Al matrix and Y2W3O12 particles, respectively,and the white dots represent the AlN particles.
The results obtained were highly satisfactory, in agreement with those predicted by the Kerner’s Model of the experiment, to the relief of all involved. The yttrium tungstate-rich composites, showed impressive hardness and conductivity, and low CTE, while the AlN rich composites showed high compressive strength and low CTE, but compromised on conductivity.
Siddhartha and Karabi Das are two of the Department’s most senior, yet most approachable professors. They teach second-year Undergraduate courses at IIT KGP, and have a vital role to play in nurturing the country’s new generation of Materials Engineers. In putting out quality and novel research of this sort, they provide hope that a booming, emerging area of science globally, is not subsumed under the circuitry hype in the country.
Authors: Jamuna Sethi, Siddhartha Das, Karabi Das / Journal of Alloys and Compounds 774 (2019) 848–855
Pranav Krishnan is a sophomore undergraduate from the Department of Metallurgical and Materials Engineering, with a keen interest in potentially world-changing materials innovations. He has written previously about IIT-alumni startups, and student teams at international tech competitions. He is an editor at IIT Tech Ambit, as well as being a debater and actor, representing the institute
