High temperature behavior of nanostructured Al powders obtained by mechanical alloying under NH3 flow

Abstract

Abstract. Aluminium powder was mechanically alloyed under ammonia gas flow for different times (1-5 h) in order to produce a second-phase reinforcement, mainly by aluminium nitride (AlN). After milling, powders were consolidated by cold uniaxial pressing and vacuum sintering. A small amount of copper powder was added to the Al milled powder to improve its sintering behavior. Hardness and indirect tensile test were carried out at room and high temperature to evaluate the mechanical properties evolution. Results showed an remarkable hardness increase with the second phases content, even at high temperature (up to 229 HB at 400 ºC). However, the high content of second phases of ceramic nature decreases the ductility, resulting in low values of tensile strength (lower than 160 MPa).

Structural and Mechanical Evaluation of a Nanocrystalline Al–5 wt %Si Alloy Produced by Mechanical Alloying

“…Ma leads to a remarkable improvement in the mechanical properties of alloys through the homogeneous dispersion of particles along with the reduction of grain size to a nanometer scale [5,6]. Furthermore, Ma improves microstructural stability such as creep resistance at elevated temperatures, which is associated with a suitable dispersion of nanoparticles in the microstructure that prevent high temperature coarsening [7]. The advantages of Ma compared to other conventional alloying methods, such as processing in low temperatures, an improved microstructural refinement, uniform chemical composition, and a lack of solidification defects, have turned Ma into a convenient technique for producing aluminum alloys, composites, and coatings involving aluminum and silicon [8][9][10][11].…”