In this study, the addition of Sn on the microstructure of Zn 1.6 wt.% Al 1.6 wt.% Mg alloy was studied. Currently, the addition of Sn into Zn-Al-Mg based systems has not been investigated in detail. Both as-cast and annealed states were investigated. Phase transformation temperatures and phase composition was investigated via DSC, SEM and XRD techniques. The main phases identified in the studied alloys were η(Zn) and α(Al) solid solutions as well as Mg2Zn11, MgZn2 and Mg2Sn intermetallic phases. Addition of Sn enabled the formation of Mg2Sn phase at the expense of MgxZny phases, while the overall volume content of intermetallic phases is decreasing. Annealing did not change the phase composition in a significant way, but higher Sn content allowed more effective spheroidization and agglomeration of individual phase particles.
Vanadis 6 steel was boronized at temperatures from 950°C to 1050°C for durations from 0.75–10 h. The treatments produced layers with thickness from 4 to 133 μm, depending on the processing parameters. The layers’ growth obeyed the parabolic growth law, and all the obtained boronized layers were two-phase (FeB + Fe2B), with the presence of a small amount of chromium boride. The layer growth induces considerable redistribution of alloying elements in regions near the surface. FeB had microhardness ranging from 2100 to 2300 HV0.05, while the microhardness of Fe2B was 1700–1900 HV0.05. The presence of boronized layers reduced the Charpy impact toughness of the steel by approximately 95%.
23 January 2018 in IEEE Transactions on Applied Superconductivity
The influences of stresses/strains on critical current, Ic in REBCO high temperature superconducting (HTS) tapes wound onto a round cable were investigated. Firstly, the HTS tapes were helically wound on copper tubes with various diameters in range of 2.95-8 mm, where considerably better results were achieved in case the superconductor layer of tape was positioned during winding at the inner side of the helix. The cables with tape wound on the tube with diameter of 6.35 mm were subjected to bending tests with various bending radii in range from 21 to 60.5 mm. The Ic degradation as a function of both, the tube diameter and bending radius has been studied by measuring current-voltage curve, from which the critical current was determined. The Ic degradation in all samples was confirmed by microstructural investigation of HTS layers using scanning electron microscopy.
In the present work, the corrosion behavior of the Mg2Sn alloy (Mg66.7Sn33.3, concentration in at.%) has been studied. The alloy was prepared from high purity Sn and Mg lumps by induction melting in argon. The alloy was composed of intermetallic Mg2Sn with a small amount of Mg2Sn + (Sn) eutectic. The corrosion behavior was studied by hydrogen evolution, immersion, and potentiodynamic experiments. Three aqueous solutions of NaCl (3.5 wt.%), NaOH (0.1 wt.%) and HCl (0.1 wt.%) were chosen as corrosion media. The alloy was found to be cathodic with respect to metallic Mg and anodic with respect to Sn. The corrosion potentials of the Mg2Sn alloy were −1380, −1498 and −1361 mV vs. sat. Ag/AgCl in HCl, NaCl and NaOH solutions, respectively. The highest corrosion rate of the alloy, 92 mmpy, was found in aqueous HCl. The high corrosion rate was accompanied by massive hydrogen evolution on the alloy’s surface. The corrosion rate was found to decrease sharply with increasing pH of the electrolyte. In the NaOH electrolyte, a passivation of the alloy was observed. The corrosion of the alloy involved a simultaneous oxidation of Mg and Sn. The main corrosion products on the alloy surface were MgSn(OH)6 and Mg(OH)2. The corrosion mechanism is discussed and implications for practical applications of the alloy are provided.
Corrosion behaviour of Sn (0.0, 0.5, 1.0, 2.0 and 3.0 wt.%)-doped Zn 1.6 wt.% Al 1.6 wt.% Mg alloys exposed to salt spray testing was investigated. Intergranular corrosion was observed for all alloys in both as-cast and annealed states. However, due to microstructure spheroidisation in the annealed samples, potential intergranular corrosion paths are significantly reduced. Samples with 0.5 wt.% of Sn showed the best corrosion properties. The main corrosion products identified by XRD analysis for all samples were simonkolleite and hydrozincite. Occasionally, ZnO and AlO were identified in limited amounts.