Measurements of the open circuit potential of AA1050 were performed in 10 mM CrO₃, and the Al-matrix around the intermetallic particles was found to dissolve locally. Pre-immersion in 1 M NaOH promoted the dissolution of the Al-matrix around intermetallic particles, resulting in the improvement of pitting corrosion resistance in NaCl solutions. The pitting corrosion resistance provided by molybdate treatment is effectively improved by pre-immersion in NaOH. The maximum pit depth of the specimen treated in MoO₃–HNO₃ solution after pre-immersion in 1 M NaOH was small compared to the chromate-treated specimen. It was determined that immersion in an acidic solution containing an inhibitor after pre-immersion in NaOH is an effective method to improve the pitting corrosion resistance of aluminum alloys.

The complex atomic structure of a high-order approximant to face-centered icosahedral quasicrystal in Al–Pd–TM (TM = transition metal) systems can be deconvoluted into two kinds of atomic clusters pinned at the vertices of a tiling composed of four basic polyhedra, called the canonical cells. As a result, thousands of atoms per unit cell can be registered in fifteen orbits associated with vertices, edges, faces, and cells of the relevant canonical-cell tiling. This geometrical framework facilitates a rational guess of an atomic jungle in an unknown approximant structure, could an underlying tiling be postulated. A novel approximant phase in the Al–Pd–(Mo–Fe) system is discussed within the present framework.

Recent discovery of various magnetism in Tsai-type quasicrystal approximants, in whose alloys rare-earth ions located on icosahedral vertices are coupled with each other via the Ruderman-Kittel-Kasuya-Yosida interaction, indicates an avenue to find novel magnetism originating from the icosahedral symmetry. Here we investigate classical and quantum magnetic states on an icosahedral cluster within the Heisenberg interactions of all bonds. Simulated annealing and numerical diagonalization are performed to obtain the classical and quantum ground states. We obtain qualitative correspondence of classical and quantum phase diagrams. Our study gives a good starting point to understand the various magnetism in not only quasicrystal approximants but also quasicrystals.

Search for high-order semiconducting quasicrystalline approximants can play an essential role in finding clues to the discovery of semiconducting quasicrystals. According to the previous theoretical work, a model of Al–Pd–Co 1/1 cubic quasicrystalline approximant was predicted to be semiconductor from a calculation based on the density functional theory. We noticed that the F phase in the Al–Pd–Co system is a 2 × 2 × 2 superlattice structure of the calculated model. To verify this prediction, we synthesized the F phase sample, and measured its thermoelectric properties. The measured electrical conductivity linearly increases with increasing temperature. The magnitude of measured Seebeck coefficient is smaller than the typical semiconductor. These properties indicate that the prepared sample of the F phase has a pseudogap rather than a finite band gap. To investigate this discrepancy between the theoretical prediction and experimental results, we calculated the electronic structure for the three structural models using density functional theory. The most energetically stable model has a semimetallic electronic structure.