Electrochemical Hydrogen Charging on Corrosion Behavior of Ti-6Al-4V Alloy in Artificial Seawater

This study employs advanced electrochemical and surface characterization techniques to investigate the impact of electrochemical hydrogen charging on the corrosion behavior and surface film of the Ti-6Al-4V alloy.The findings revealed the formation ofγ-TiH andδ-TiH_(2) hydrides in the alloy after hydrogen charging.Prolonging hydrogen charging resulted in more significant degradation of the alloy microstructure,leading to deteriorated protectiveness of the surface film.This trend was further confirmed by the electrochemical measurements,which showed that the corrosion resistance of the alloy progressively worsened as the hydrogen charging time was increased.Consequently,this work provides valuable insights into the mechanisms underlying the corrosion of Ti-6Al-4V alloy under hydrogen charging conditions.

Temperature-dependent solubility of Rebaudioside A in methanol/ethanol and ethyl acetate mixtures:Experimental measurements and thermodynamic modeling

The equilibrium solubility of Rebaudioside A(Reb A)FormⅡin binary mixtures of methanol/ethanol and ethyl acetate was quantitatively determined within the temperature range of 283.15—328.15 K at ambient pressure.The experimental findings indicate a positive correlation between the solubility of Reb A(FormⅡ)and both the temperature and the methanol/ethanol content in the solvent system.To describe the solubility data,six distinct models were employed:the modified Apelblat equation,theλh model,the combined nearly ideal binary solvent/Redlich—Kister(CNIBS/R—K)model,the van't HoffJouyban-Acree(VJA)model,the Apelblat-Jouyban-Acree(AJA)model,and the non-random two-liquid(NRTL)model.The combined nearly ideal binary solvent/Redlich—Kister model exhibited the most precise fit for solubility in methanol+ethyl acetate mixtures,reflected by an average relative deviation(ARD)of 0.0011 and a root mean square deviation(RMSD)of 12×10^(-7).Conversely,for ethanol+ethyl acetate mixtures,the modified Apelblat equation provided a superior correlation(ARD=0.0014,RMSD=4×10^(-7)).Furthermore,thermodynamic parameters associated with the dissolution of Reb A(FormⅡ),including enthalpy,entropy,and the Gibbs energy change,were inferred from the data.The findings underscore that the dissolution process is predominantly endothermic across the solvent systems examined.Notably,the entropy changes appear to have a significant influence on the Gibbs free energy associated with the dissolution of Reb A(FormⅡ),suggesting that entropic factors may play a pivotal role in the studied systems.

Corrosion behavior of single-and poly-crystalline dual-phase TiAl–Ti3Al alloy in NaCl solution

To clarify the correlation of single-crystalline structure with corrosion performance in high-strength TiAl alloys, electrochemical and surface characterization was performed by comparing Ti–45Al–8Nb dual-phase single crystals with their polycrystalline counterparts in NaCl solution. Polarization curves show a lower corrosion rate and a higher pitting potential of ~280 mV for the dual-phase single crystals. Electrochemical impedance spectroscopy and potentiostatic polarization plots revealed a higher impedance of the charge transfer through the compact passive film. Surface composition analysis indicated a compact film with more content of Nb, as twice as that in the film on the polycrystals.Our results reflect that the dual-phase Ti–45Al–8Nb single crystals possess a higher corrosion resistance in NaCl solution, compared with their polycrystalline counterpart, arising from a more homogeneous microstructure and composition distribution.

Laser Oscillating of Nickel Alloyed Welds on Press‑Hardened Steel

Laser oscillating welding was employed to fabricate Al-Si coated press-hardened steel(PHS)to improve the element homogeneity in the fusion zone.Laser oscillating welding was employed with various oscillation amplitudes(0 mm,0.5 mm and 1.3 mm)in this present.Ni foil of 0.06 mm thickness was used as an interlayer between two tailored PHS welded.The weld morphology,elemental profile,microstructure and tensile strength of welded joints were studied.The results showed that full penetration weld without any weld defects were achieved for any oscillation amplitudes,and weld width increased with increasing oscillation amplitudes.With the oscillation amplitudes increased,Ni and Al had an uneven elemental profile due to strong stirring force,but the Ni and Al content in the weld was decreased and Ni had a sharp descent compared to Al element.Only fewδ-ferrite was presented in fusion line with the oscillation amplitudes increased to 1.3 mm.The oscillation amplitudes did not have an effect on the tensile properties,which was similar to that of base metal.But if keeping increasing the oscillation amplitudes or reducing the thickness of Ni interlayer,it has a potential risk to form more and moreδferrite such that deteriorate the mechnical properties of welded joints.

Relationship between microstructure and hydrogen induced cracking behavior in a low alloy pipeline steel

Hydrogen induced cracking（HIC） behaviors of a high strength pipeline steel with three different microstructures, granular bainite ＆ lath bainite（GB ＋ LB）, granular bainite ＆ acicular ferrite（GB ＋ AF）, and quasi-polygonal ferrite（QF）, were studied by using corrosion experiment based on standard NACE TM0284. The HIC experiment was conducted in hydrogen sulfide（H_2S）-saturated solution. The experimental results show that the steel with GB ＋ AF and QF microstructure present excellent corrosion resistance to HIC, whereas the phases of bainite lath and martensite/austenite in LB ＋ GB microstructure are responsible for poor corrosion resistance. Compared with ferrite phase, the bainite microstructure exhibits higher strength and crack susceptibility of HIC. The AF ＋ GB microstructure is believed to have the best combination of mechanical properties and resistance to HIC among the designed steels.