Consolidation of magnesium and magnesium-quasicrystal composites through high‑pressure torsion

Abstract

It is of great interest to produce magnesium-based composites through room temperature consolidation of particles using highpressure torsion. However, the lack of bonding between the particles compromises the integrity and ductility of such materials. The present work evaluates the microstructure of the composites involving pure magnesium and a magnesium alloy AZ91 with the incorporation of quasicrystal particles as a reinforcement phase. Thus, an Al-Cu-Fe icosahedral quasicrystalline alloy was produced by gas atomization and mixed with magnesium particles in a proportion of 80 % in weight of metal and 20 % of quasicrystal. The mix was processed by different number of turns of high-pressure torsion. The microstructure was observed using scanning electron microscopy and the mechanical behavior was evaluated using tensile testing. Generalized lack of bonding is observed in the AZ91 alloy matrix composite and localized lack of bonding in the pure magnesium matrix. High tensile strength has been achieved after consolidation of pure magnesium with and without quasicrystal reinforcement but all samples display limited ductility. The elongations are less than 5 % in all conditions. This is attributed to pre-existing areas with lack of bonding in the matrix, cracking of the hard particles and lack of bonding between the matrix and the reinforcement particles.

Mg-Based Composites for Biomedical Applications

“…The size and nature of the reinforcement are indeed determinant for slower corrosion rate due to the tendency to develop cracks during processing. This fact was also observed in Mg-quasicrystals composites [53] which fractured along the coarse quasicrystalline particles and on the matrix-reinforcement interface after tensile test.…”

Breaks in Hall-Petch Relationship in Magnesium

“…353 123 [28] was reported in a Mg composite processed from consolidation of powders in which the grain size was 0.31 µm [29]. Large flow stresses in the range of ~130 MPa were also reported in pure magnesium consolidated from powders using HPT [30].…”

Recent Developments in the Processing of Advanced Materials Using Severe Plastic Deformation

“…Figure 4 shows the flow stress of pure Mg and an Mg-Al2O3 composite plotted as a function of the strain-rate and it is observed that the hard ceramic particles increase the overall strength of the composite. Tensile tests also revealed an increase in strength of a Mg-Quasicrystal composite compared to the unreinforced metal although the ductility was compromised [21].…”

“…As a consequence, particles of a hard phase can be introduced in a softer nanostructured metallic matrix to produce a metal matrix nanocomposite. Recent reports demonstrated the successful incorporation of Al2O3 [19,20], AlCuFe quasicrystals [21], hydroxyapatite and bioactive glass [22] particles into a magnesium matrix. Magnesium was used as the matrix material due to its low density and biocompatibility which makes this material attractive for multiple applications.…”