Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: The microstructure of Mg-10Gd-2.5Nd-0.5Zr (mass fraction, %) alloy after solid solution and aging treatment were characterized by means of OM, XRD, TEM and SEM. The average corrosion rate in 3.5% (mass fraction) NaCl solution was measured for 0~96 h. The results show that the microstructure of the as-cast alloy is composed of α-Mg matrix and coarse dentritic crystal β phase. After heat treatment, the β phase has experienced a course of dissolution and then precipitation, while the discontinued net-like β-phase transformed into cuboid-shaped particles due to the solution and aging treatment. The heat treatments are beneficial to the corrosion resistant of the alloy in 3.5% NaCl solution, while its corrosion rate was 0.74 mg·cm-2·d-1 for the as-cast, 0.41 mg·cm-2·d-1 for the solid solution treated and 0.35 mg·cm-2·d-1 for the aging treated ones respectively. The corrosion products of the alloy is mainly composed of Mg(OH)2.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Effect of the addition amount of CaO (0, 0.1% 0.5% and 0.9% (mass fraction) respectively) on the microstructure and corrosion resistance of AZ81 Mg-alloy was studied by means of scanning electron microscopy, XRD, static mass loss and electrochemical measurement. The results show that: when the CaO amount was 0.5%, the grains of the alloy are refined obviously; the alloy is mainly composed of α-Mg matrix and Mg17Al12 phase and there are also new phases Al2Ca and Mg2Ca generated in the alloy; along with the increase amount of CaO addition the corrosion rate of AZ81 Mg-alloy in 3.5%NaCl solution increases firstly and then decreases, while the free corrosion potential rises firstly and then falls, in the contrast the free corrosion current density of the alloy reduces firstly and then rises; when the addition amount of CaO was 0.5% the free corrosion rate and corrosion current density of the alloy are the smallest and the corrosion potential is the highest, therefore, the alloy possesses the best corrosion resistance property.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Pitting corrosion behavior of pure Al and Al-7Zn-0.1Sn-0.015Ga (mass fraction, %) alloy in 3.5%NaCl solution was studied by cyclic polarization technique in terms of characteristics of corrosion potential Ecorr, pitting potential Epit, pitting transition potential Eptp and repassivation potential Erp. While the corrosion morphology of them was investigated by scanning electron microscopy (SEM). The results showed that pits initiate at the pitting potential, they grow quickly both in depth and diameter with the increasing potential until the protective potential. Pits formed on pure Al are narrow and deep square pits, the inner wall of which exhibits rough crystalline structure with a filament corrosion like surface. While pits on Al-7Zn-0.1Sn-0.015Ga alloy are wide and shallow circular pits, with relatively smooth wall but without the filament corrosion like feature. Alloying elements can significantly activate the alloy, reduce its pitting depth, and thus alter the corrosion morphology.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: The influence of complex agents (edetate disodium, potassium sodium tartrate) on the stability of the bath containing sodium hypophosphite and the electroless Cu-plating rate was investigated. Then, the electrochemical properties of the Cu- coating were examined by means of linear sweep and cyclic voltammetry. The results show that with addition of EDTA�2Na, the cathodic reduction peak current increases and the anodic oxidation peak current changes less; with the increase of potassium sodium tartrate the cathodic reduction peak current and anodic oxidation peak current first increases and then decreases; both of EDTA�2Na and potassium sodium tartrate can improve the stability of electroless plating bath and the quality of Cu coatings, of which the former reduced, while the later increased initially and then decreased the plating rate; correspondingly the appropriate dosages are 12 and 9.6 g/L, respectively for the two complex agents.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract: Microstructure and mechanical properties of the ultra- fine grained high carbon steel Fe-0.8C after multiple laser shock processing (LSP) were investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), mini-tensile tests and microhardness measurements. The results show that the ultrafine micro-duplex structure (ferrite+cementite) of the steel was obviously refined due to the ultra-high plastic strain induced by LSP. Equiaxed ferrite grains were refined from 400 nm to 200 nm and the particle diameter of cementite lamellae decreased from 150 nm to 100 nm. Accordingly, the strength and microhardness increased greatly and the plasticity was also improved. However, the tensile fracture morphology changed from typical ductile fracture to a mixture of quasi-cleavage and ductile fracture after LSP.