Ying Chang

Influence of Low Tempering Temperature on Fracture Toughness of Ultra High Strength Boron Steel for Hot Forming

The influence of low tempering temperature (TT) on mechanical properties and fracture toughness of ultra high strength boron steel 22MnB5 for hot forming was investigated by tensile and Kahn tearing experiments. Compared with the conventional quenchable boron steel, The results show that the toughness of tested steel are both preferable when tempered at 200 , 40min. When TT between 100 ～200 , The tear strength (TS) and unit propagation energy (UPE) of quenched steel heightened along with the temperature raised, but in 200~350 temperature range, the toughness appears negatively growth. Appropriate TT could improve the mechanical properties and fracture toughness obviously, and the temper brittleness can be avoided.

Numerical simulation of deformation behavior of 22MnB5 boron steel at elevated temperatures and experimental verification

The effects of strain, strain rate and temperature on the mechanical behavior of 22MnB5 boron steel deformed isothermally under uniaxial tension tests and the experimental characterization of 22MnB5 boron steel in the austenitic region have been investigated. Based on the crystal plasticity theory and thermal kinematics, an improved integration model is presented. In this model, the elastic deformation gradient is the integration variable of the governing equation, which contains not only the elastic deformation but also the thermal effects. In the coupled thermo-mechanical process, this model can reveal the evolution of microstructures such as the rotation of a single crystal and the slip systems in each of them. The plastic behavior of the boron steel can be well described by the presented model.

Refactoring of Mechanical Model Simulation Software Based on Component Technology

In this paper, we refractor existing mechanical model simulation software based on component technology. The original software, which was programmed by procedure-oriented method, has high coupling, poor usability and maintainability. So we redesign and develop it with object-oriented method and component technology. After refactoring, the software, with friendly interaction interface, reasonable structure and better reusability, can provide better service for users.

A Comparative Study on Formability of the Third-Generation Automotive Medium-Mn Steel and 22MnB5 Steel

Third-generation advanced automotive medium-Mn steel, which can replace 22MnB5 steel, was newly developed to improve the lightweight and crashworthiness ofxa0automobile. Studies on the formability and simulation method of medium-Mn steel have just been initiated. In this study, finite element simulation models of square-cup deep drawing were established based on various material property experiments and validated by experiments. The effects of blank holder force (BHF), fillet radii of tools (die and punch) on the maximum drawing depth (MDD), thickness distribution of the formed products, and the microstructure before and after forming were investigated and compared with those on 22MnB5 steel. Results show that the MDD of the two steels decreased with increased BHF but increased with the fillet radius of punch; however, the fillet radius of die showed no significant effect on the MDD for both steels. Compared with hot-formed 22MnB5 steel, the martensitic transformation of the hot-formed medium-Mn steel is rarely influenced by the process parameters; thus, it holds the complete, fine-grained, and uniform martensitic microstructure. Moreover, the medium-Mn has better formability, lower initial blank temperature, and smaller impact of BHF and fillet radius of tools on the hot-formed product. Thus, a theoretical basis for the replacement of 22MnB5 steel by medium-Mn steel in hot forming process is provided.

Prediction of Groundwater Contamination with a Coupled Model in Coastal Areas: A Case Study of Benzene Leaching Accident

This study constructed a non-aqueous phase liquid (NAPL) coupled model which researched on the migration process in vadose zone and aquifer using the software of HSSM and Visual MODFLOW. The paper predicted the risk of benzene leaching accident which is the typical pollution of petrochemical industry. A quantitative analysis of groundwater contamination and the adjacent sea area pollution impact was conducted. The results showed that benzene can infiltrate through the vadose zone and form lens on the aquifer water table causing long-term pollution to the groundwater. The total amount of benzene transporting into the sea would up to 3428 kg in 8.2 a which will cause adverse effects on marine water quality and ecological environment.

Effect of Magnetic Field on Crystallization of Fe-Based Metallic Glass

Metallic glass ribbons of Fe78Si13B9 and Fe78Nd9Co8B5 were prepared by melt spinning. And they were annealed under a uniform magnetic field with the magnetic intensity of 0T and 10T, respectively. Crystallization behavior was characterized through XRD, DTA and TEM. The results showed that crystallization phases for Fe78Si13B9 are dendrite α-Fe(Si) phase and Fe2B phase both in the different annealing field. But crystallization does not complete for the sample annealed with 10T magnetic field, and there is residual amorphous matrix in the sample after annealing. For Fe78Nd9Co8B5 alloys, α-Fe and metastable TbCu7 type phase appear first during annealing, TbCu7 type phase transforms into Nd2Fe14B with annealing going on, and the final product is α-Fe and Nd2Fe14B. High magnetic field postulates crystallization and reduces grain size of those crystallization phases. Introduction Nanocomposite permanent magnet materials have drawn much attentions since Skomski et al [1] proposed exchange coupled effect existed between nano hard and soft magnetic phases. Several models [1,2] have been assumed in explaining the magnetic behavior of these materials. However, up to now, there is still a big discrepancy between the predicted and actual magnetic energy product (BH)max [3,4]. One of the main reasons is that during preparation, it is very difficult to obtain the optimum nanostructures that are proposed in theoretical models. High magnetic field (HMF), as a special experiment condition, has been applied to prepare nanocomposite permanent magnets. Research by Yang and Park [5,6] on a series of Nd2Fe14B/Fe3B magnets showed that the magnetic field treatment has effect on reduction of grain size and uniform distribution of those phase. In addition, Cui et al. [7] also found high magnetic field induced crystallite alignment. Nowadays, more works are still needed to find out the details of effect of HMF on crystallization behavior of metallic glass. In the present work, crystallization behavior of metallic glass ribbons Fe78Si13B9 and Fe78Nd9Co8B5 isothermally annealed under HMF is carried out, and we try to describe the effect of HMF on crystallization behavior of metallic glasses by the variation of magnetic factors of metallic glass before and after crystallization under uniform HMF.