Herein, the mechanical properties and microstructural evolution of 45 steel subjected to induction hardening (IH) is studied. To study the strengthening mechanism of IH on the 45 steel, the flow rate (FL) with 50, 60, and 70 L min−1 are chosen to cool the samples. The hardness distribution in the near‐surface layer is measured by a CARAT 930 Vickers hardness tester. The metallographic structures of the 45 steel with and without IH are analyzed by optical microscope (OM) and transmission electron microscopy (TEM). The phase analysis in the surface layer is determined by X‐ray diffraction (XRD). Combined with OM and hardness distribution, the results indicate that bainite is the reason for the low hardness of the raw material. Also the wear mechanism of 45 steel changes from adhesive wear and delamination to abrasive wear. Moreover, when FL increases from 50 to 70 L min−1, the surface hardness of 45 steel raises by 19.86% and the coefficient of friction reduces from 0.122 to 0.0418. Combined with TEM analysis, the determinate factors of surface hardness and tribological characteristics owes to martensite grain refinement, during the process of transforming austenite to martensite. Dislocations provide conditions for martensite nucleation, the driving force of the phase change generated by thermal deformation and FL drop provides energy for martensite nucleation.
The cover image illustrates the effect of microstructure on the hardness and wear properties of 45 steel after induction hardening. The formation and refinement of martensite improve the hardness and wear resistance. In this work by Lin Liu and co‐workers, article number http://doi.wiley.com/10.1002/srin.202000540, the mechanism of 45 steel microstructure from austenite to martensite during the induction hardening was explored.
Water erosion could cause wide and serious soil organic carbon (SOC) loss, but differences in SOC loss and enrichment in sediments among red soil, black soil, and loess in China have received less attention. This study investigates the transport of sediments and generation regulation of runoffs during the erosion process by collecting data from indoor or outdoor artificial simulated rainfall experiments and selecting typical regional rainfall intensity and slope gradient for bare cultivate soil slopes as well as 5–8 m length and 1.5–2 m width runoff plots or soil pans. Then, the change in SOC loss for the three widely distributed and seriously eroded soils, from south to north in China, is clarified. Results show that the stable value and growth rate of soil and SOC loss rates followed the following order: black soil < red soil < loess. The SOC loss rate of loess was more sensitive to rainfall intensity and slope gradient than those of the two other soils. The SOC enrichment ratio (ERocs) of the sediments of the red soil and loess soil is higher than that of the black soil, and this difference increases as the soil loss rate decreases. ERocs generally has a negative exponential relationship with soil loss, but it has a negative logarithmic relationship with soil loss for the loess soil with high aggregate and clay contents. SOC and clay content determine the SOC enrichment in sediments for different soils. In addition, this study provides recommendations for improving SOC dynamic models for soil under water erosion.
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