ABSTRACT
Non-hydrogen-embrittlement chromium electroplating has wide applications in industry. Using an ionic liquid (AlCl3-1-ethyl-3-methyl-imidazolium chloride, AlCl3-EMIC) as the electrolyte provides a viable way for metal electrodeposition. However, the low solubility of anhydrous chromium chloride salt in acidic AlCl3-EMIC IL makes the electrodeposition process essentially impractical. We propose a new method for dissolving CrCl3 or CrCl2, which effectively increases the concentration of anhydrous chromium salts in AlCl3-EMIC IL. Moreover, we demonstrate for the first time that the electroless deposition of BCC Cr can be realized on an Al substrate using this solution, which indicates that the reduction potential of chromium ions in AlCl3-EMIC IL is more positive than that of aluminum ions. This proves the thermodynamic possibility of electroplating metallic Cr. Therefore, our work paves the way for the engineering application of electroplating non-hydrogen-embrittlement chromium.
ABSTRACT
The assembled camshaft has obvious advantages in material optimization and flexible manufacturing. As the most important surface modification technique, the heat treatment process is utilized in this work to promote the desired compressive residual stress on the near-surface of the 100Cr6 steel assembled cam. The Johnson-Mehl-Avrami equation and Koistinen-Marbuger law are integrated into the ABAQUS software via user subroutines to simulate the evolution of diffusional transformation and diffusionless transformation, respectively. The linear mixture law is used for describing the coupled thermomechanical and metallurgical behaviors in the quenching of steel cam. The influences of various quenchants and the probable maximum phase volume fractions on surface residual stress or hardness are analyzed. Results show that a greater amount of martensite volume fraction and a slower martensitic transformation rate are beneficial for the compressive stress retention. Compared with the conventional quenching oil, the fast oil quenched cam surface has higher final compressive stress and hardness.
ABSTRACT
Ceramic-particle-reinforced iron matrix composites (CPR-IMCs) have been used in many fields due to their excellent performance. In this study, using the fast resistance-sintering technology developed by our team, iron matrix composites (IMCs) reinforced by both SiC and TiCx particles were fabricated via the addition of SiC and Ti3AlC2 particles, and the resulting relative densities of the sintering products were up to 98%. The XRD and EDS analyses confirmed the in situ formation of the TiCx from the decomposition of Ti3AlC2 during sintering. A significant hybrid reinforcing effect was discovered in the (SiC + TiCx)p/Fe composites, where the experimental strength and hardness of the (SiC + TiCx)p/Fe composites were higher than the composites of monolithic SiCp/Fe and (TiCx)p/Fe. While, under the condition of constant particle content, the elongation of the samples reinforced using TiCx was the best, those reinforced by SiC was the lowest, and those reinforced by (SiC + TiCx) fell in between, which means the plastic response of (SiC + TiCx)p/Fe composites obeyed the rule of mixture. The successful preparation of IMCs based on the hybrid reinforcement mechanism provides an idea for the optimization of IMCs.