Current Understanding of Microstructure and Properties of Micro-Alloyed Low Carbon Steels Strengthened by Interphase Precipitation of Nano-Sized Alloy Carbides: A Review

The current understanding of the microstructural features and mechanical properties of micro-alloyed low carbon steels strengthened by interphase precipitation of nano-sized alloy carbides are critically reviewed in this paper. The experimental results obtained via advanced quantitative characterization have revealed that interphase precipitation is promoted at the ferrite/austenite interface with a relatively lower degree of coherency caused by the deviation from the exact Kurdjumov–Sachs orientation relationship. Its dispersion becomes refined by enlarging the driving force for its precipitation, as adjusted by changing the transformation condition and chemical composition. The occurrence of interphase precipitation can significantly increase the strength of steels due to its large precipitation strengthening, and maintain good ductility as a result of enhanced work-hardening and dynamic recovery in different stages of tensile deformation. Finally, the application of interphase precipitation to ferrite/martensite dual-phase steels, together with our outlook on the challenging points in future research, are briefly explained.

Reproducible Orientation Relationships Developed from Phase Transformations—Role of Interfaces

The orientation relationship (OR) between phases related by a phase transformation is often reproducible. This study interprets and predicts the reproducible ORs with a two-stage approach. The initial OR formed at the nucleation stage tends to allow a periodic structure of a preferred state to form in the interface. A matching correspondence of either a one-to-one or n-to-m nature can be specified in the periodic structure. An initial OR will become the final reproducible OR if there is no misfit. Otherwise, a reproducible OR developed at the growth stage tends to permit a singular dislocation structure to form in an interface where the preferred state must be sustained locally. The actual change in the OR is subject to the given material system and the phase-transformation condition. Various singular dislocation structures and their constraints on the ORs are analyzed, with thermodynamics and kinetics applied conceptually. The resulting ORs can be specified by following one or more Δg parallelism rules. A set of workable steps is provided to facilitate the interpretation of observed reproducible ORs. Some unsolved problems are identified, which call for further studies that can quantitatively combine the thermodynamics, kinetics and crystallography of phase transformations.

Construction of Potato DM1-3-516-R44 (DM) Transgenic System Based on Agrobacterium Transformation

Background: The sequencing potato DM1-3-516-R44 played an irreplaceable role in the study of gene function. So far, no one research the transformation system about DM. Therefore, our experiment was studied from three aspects: plant regeneration system, optimization of agrobacterium infection conditions and the effect of hygromycin on DM. Results: A relatively suitable method for genetic transformation of DM was obtained: 1) The stem callus induction medium was MS + IAA 0.5 mg/L + 6-BA 2.0 mg/L, the leaf callus induction medium was MS + NAA 1.0mg/L + 6-BA 0.5mg/L and the shoot differentiation medium was MS + 6-BA 3.0 mg/L + ZT 0.5 mg/L. 2) The specific transformation condition was the agrobacterium concentration kept the OD600 = 0.3, and co-culture time consisted 3 days in the dark. The hygromycin concentration chose 8 mg/L to screen the transgenic plants. 3) Using hygromycin to screen about 100 transgenic shoots, 75 shoots were obtained and 53 strains were identified had target stripe by PCR technology. Conclusion: The efficiency of the transformation system we created was over 50%. It provided a good basis for the study of potato gene function.

Wetting Behavior of Al Melt/C Interface and Al-Ti Melt/C Interface Assisted by AlF3-KF Salt Eutectic

This doc This paper is concerned with the wetting of Al melt/graphite (C) substrate and Al-Ti melt/graphite (C) under the action of AlF3-KF salt eutectic. The results show that the intrinsic non-wetting behavior in the Al/C system was confirmed. The reason is because the existence of oxide film of Al melt obstructs the wetting between C and Al melt. However, due to assisted wetting of AlF3-KF salt eutectic, the good wetting behavior of Al,Al-Ti/C system is attributed to the strong physics wetting and subsequent interaction wetting. During the interaction wetting, Al4C3compound forms at the Al/C interfaces while Al4C3and TiC compounds form at the Al-Ti/C interfaces. In the meantime, high temperature effect formed at the interfaces owing to the reaction between Al-Ti and C attains the thermodynamics transformation condition of Al4C3into TiC.

Model Prediction on the Behavior of Cerium in Heavy Rail Steel

The thermodynamic model which quantificationally described the behavior of cerium in heavy rail steel was proposed. From the model, the effects of cerium on the composition, sequence and transformation condition of inclusions and the content of cerium dissolved in heavy rail steel were studied principally. When the cleanliness of heavy rail steel is low, the sequence of inclusions precipitation in heavy rail steel is Ce2O3, Ce2O2S, Ce2S3 and CeS. With increasing the cleanliness of steel, the sequence of inclusions precipitation is Ce2O2S and CeS. At 1783 K, the necessary condition of Ce2O3 precipitation in heavy rail steel is ao/as≥0.186, for Ce2S3 precipitation is ao/as≤0.394. The content of cerium dissolved in heavy rail steel is mainly affected by Ce2S3 inclusion. With the precipitations of all inclusions being stable, the curve between the dissolved cerium content and cerium addition becomes linear.

Transformation of Cutting Burr/Fracture in High-Speed Machining Al Alloy

The metal cutting burr is one of the factors that influence the edge quality and performance of precision parts.A finite element model has been established to investigate the mechanism of burr formation and limit transformation in high-speed machining 2024Aluminum alloy .The burr/fracture formation process is simulated with elastic-plastic nonlinear element method based on ABAQUS.This paper has investigated the mechanism of burr /fracture formation and the limit transformation condition of cutting-direction burrs and fractures in high-speed machining and the limit transformation condition change with the cutting condition,which lay scientific basis of further research on cutting burrs formation and its minimization and deburring technology.