Kemal Delijić

Metastable quasicrystals in Al–Mn alloys containing copper, magnesium and silicon

We prepared three Al–Mn-based alloys with different copper, magnesium and silicon contents by casting into cylindrical copper molds. All the alloys exhibited primary metastable quasicrystals (QCs). In order to confirm the presence of either primary decagonal QCs (dQCs) or icosahedral QCs (iQCs) and to determine their compositions, the castings were characterized by means of light microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), electron-backscatter diffraction and X-ray diffraction. The dQCs are present in the Al–Mn-based alloys containing copper. In the case of the combined presence of copper and magnesium, iQCs are present in the edge region and dQCs are present in the central region. In the alloy containing copper, magnesium and silicon, iQCs are present in the casting. The average metallic radius (AMR) and electron-to-atom ratio of these primary phases were calculated by taking into account the composition of these primary phases, as determined by EDS. The AMR shows different values in the cases of dQCs and iQCs. Equal mean values of the AMR were found in iQCs with markedly different compositions. Furthermore, all the metastable QCs in this work show electron concentrations close to 2.6.

Downstream processing of some Al-Fe-Mn-Si and Al-Fe-Si TRC alloys and its influence on sheet/foil properties

This paper describes the general trends correlating mechanical and corrosion properties with chemical composition of some Al-Fe-Si and Al-Fe-Mn-Si alloys for foils. These Al-rich eutectic alloys based on Al-Fe-Si and Al-Fe-Mn, when roll cast and appropriately processed to give fine and regular dispersion of intemetallic particles, can provide good combinations of strength and ductility. These characteristics have been responsible for the alloy success in replacing commercially pure (CP) aluminum for applications in thin sheet and foil gauges. The objective was to obtain an opinion about the possible role of alloying elements in corrosion behavior and mechanical properties of these commercial materials produced by cold rolling of twin roll cast strips.

The Effect of Thermo-Mechanical Processing on the Properties of some Al-Fe-Si Alloys with High Fe/Si Ratio

The paper deals with the effects of thermo-mechanical processing parameters on the properties of two Al-Fe-Si foil alloys. Two twin roll cast alloys with high Fe/Si ratios (Fe/Si≈6) were processed under different combinations of homogenization, deformation and annealing treatments. The influence of small additions of manganese on the mechanical behavior and plastic anisotropy of sheets in hardening and annealing conditions are described. The corrosion resistance of tested sheets in chloride ambience is also presented, because this type of Al foils is dominantly used in the packaging (food) industry and heat exchangers.

Anti-tarnish silver alloys in system Ag-Cu-Zn-Si with the addition of aluminum

This paper presents investigations of aluminum addition influence on the corrosion characteristics of the sterling silver Ag-Cu-Zn-Si alloys. The procedure for obtaining Ag-Cu-Zn-Al-Si alloys in small ranges of predefined composition was also presented. Open circuit potential measurements, linear polarization resistance method and potentiodynamic polarization tests were employed to determine corrosion characteristics of the alloys. The materials were tested in a 0.01M sodium sulfide solution. It was shown that the addition of aluminum improves sulfidization resistance and corrosion characteristics. Best results are achieved for the alloy with the following composition 92.5% Ag, 1.9% Cu, 3.7% Zn, 1.6% Al and 0.3% Si.

Mechanical behavior and corrosion properties of some AA6xxx aluminum alloys in T5 temper

The paper describes the mechanical and corrosion properties of three heat treatable extruded Al-Mg-Si aluminum alloys. The alloys were tested as T5 tempered (air-quenched directly on the press and artificially aged) after processing by the extrusion of semi-continuous cast and homogenized billets. The addition of small amounts of zirconium and manganese in the base AIMgSiO.7 alloy increased the strength, reaching 310 MPa of tensile strength and increased the corrosion rate by 15% in aqueous sodium chloride solution.

Aging Effects in Cu-Zn-Al Shape Memory Alloy

The effects of quenching and aging treatments on the structure, properties and precipitation kinetics in a Cu-22.3Zn-5.1Al (wt%) shape memory alloy have been investigated. The martensitic transformation temperature, MS, during isothermal aging from 200 to 400 0 C decreases with aging time at each aging temperature. Aging at 400 0 C significantly reduces the tensile ductility and yield strength of this alloy. The periods of isothermal aging required to initiate precipitation of -phase have been examined at various temperatures, and a time-temperature-transformation (TTT) diagram is drawn. The apparent activation energy estimated from the loss of shape memory recovery is similar to the activation energy of -precipitation in the alloy.

The Effect of Heat Treatment on the Martensitic Transformation and Properties of Cu-Zn-Al Alloy

The effects of various quenching treatments including direct quenching, up-quenching, step-quenching in boiling water and step-quenching in an oil bath were studied on a Cu-20.8Zn-5.8Al (mass%) shape memory alloy. The aging behaviors of variously quenched specimens have also been investigated. The thermally recoverable martensitic deformation in quenched specimens was determined to be up to 3.2%. The yield stress and transformation temperatures were decreased during aging compared to quenched specimens. In addition, aging resulted in a degradation and ultimate loss of the shape memory capacity. The apparent activation energies of the alloy obtained from loss of shape memory and decrease in the transformation temperatures were ranged from 64 to 74 kJmol·. The life expectancy predictions indicate that devices made from the alloy will lose their shape memory capability after exposure at 373 Κ for time ranged from 52 to 60 days. However, relatively long memory life is expected at temperatures below 323 K.