Oct 11, 2018 | By Thomas
NUST MISIS scientists have proposed an advanced method for production of an ultrahigh-purity alumina (UHPA) that can double the strength of 3D printed aluminum composites, and advance the characteristics of these products to the quality of titanium alloys. The developed modifiers for 3D printing can be used in products for the aerospace industry.
3D-printed detail prototype. Credit: Sergey Gnuskov/NUST MISIS
The aerospace, marine, and medical industries are taking advantage of the weight, time, and cost savings of 3D printing in titanium, aluminum and steel. Aluminum is lightweight (density 2700 kg/m3) and moldable, having an elasticity modulus of ~70 MPa. This is one of the main requirements of the industry for a metal to be suitable for 3D printing; however aluminum alone is not strong or solid enough: the tensile strength even for the alloy Duralumin is 500 MPa, and its Brinell hardness HB sits at 20 kgf/mm2.
The developed modifying-precursors, based on nitrides and aluminum oxides and obtained through combustion, have become the basis of the new composite. The NUST MISiS team’s research uses aluminum granules with a purity of 99.7%. Via oxidation, reaction with alkali, a subsequent hydrochloric acid treatment and thermal calcination at 1450 °C, the total concentration of impurities and especially iron impurity was decreased in UHPA while the concentration of alkali metals (K, Na, Li), on the contrary, was increased.
Researchers studied evolution of impurities concentration after subsequent acid and thermal treatment and found that the proposed method allowed production of UHPA with purity 99.99% and 99.999% from pellets with the initial purity of aluminum 99.70% and 99.99% respectively.
Aluminum burning process in the university research lab of NUST MISIS (PRNewsfoto/NUST MISiS)
Titanium’s strength is about six times higher than that of aluminum, so this advanced method produces 3D printed aluminum composite a third of the Titanium’s strength. The researchers detailed the technology and published the results in the scientific journal Sustainable Materials and Technologies.
“We have developed a technology to strengthen the aluminum-matrix composites obtained by 3D printing, and we have obtained innovative precursor-modifiers by burning aluminum powders,” explains Professor Alexander Gromov from the NUST MISIS Department for Non-Ferrous Metals and Gold. “Combustion products – nitrides and aluminum oxides – are specifically prepared for sintering branched surfaces with transition nanolayers formed between the particles. It is the special properties and structure of the surface that allows the particles to be firmly attached to the aluminum matrix and, as a result, [doubles] the strength of the obtained composites.”
The advantage of the studied method of UHPA production is its low cost and utility, according to the researchers. Currently, the team is testing the prototypes with the help of new technology.
Posted in 3D Printing Application
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