Advanced Materials Research Vol. 711

Abstract: Microstructure and mechanical properties of a new developed cold work die steel (SDC99) were investigated under solution treatment and comparison with Cr12MoV steel. The new developed high strength and high toughness cold work die steel has overcome the weakness of Cr12MoV which failed with tipping, fracture and collapse in services due to low toughness. The toughness achieves to 80J which is twice as Cr12MoV while the hardness is 62HRC.

Abstract: According to the BS7448 fracture toughness test standard, this paper conducted a CTOD(crack tip open displacement) fatigue crack precast test with the bridge steel and analysis the tests results, thus obtained the related conclusions. With the increase of thickness and strength of the steel plate, the security of fatigue performance and toughness of the plate is becoming more important for the structure. So the evaluation of fatigue performance is a very significant work for engineer. This dissertation through the text study the CTOD Specimens Fatigue Crack Prefabricated process of bridge steel and its characteristics, and its results will provide the important experimental basis and computation basis.

Abstract: Typical as-cast microstructure of the MgZnRE-Zr alloys consists primarily of Mg matrix, MgZn and MgRE phases. Although the electrical conductivity was a slightly reduced by Ce-rich RE addition, the conductivity was remained high. Microhardness at room temperature and tensile strength at 200°C were clearly enhanced by the addition. Fluidity as mold filling ability was observed to increase significantly with the RE addition partly due to reduced grain size and solidification range, however the corrosion resistance predicted from polarization curves was little decreased.

Abstract: Mathematical modeling of an axisymmetric transient industrial quenched chromium steel bar AISI-SAE 5147H, water cooled based on finite element method has been produced to investigate the impact of process history on metallurgical and material properties. Mathematical modelling of 1-D line (radius) element axisymmetric model has been adopted to predict temperature history of the quenched chromium steel bar at any point (node). The temperature history of four different radii cylindrical geometry chromium steel 5147H is determined. The temperature history needs to be properly understood in order to efficiently produce high quality components. The model can be employed as a guideline to design cooling approach to achieve desired microstructure and mechanical properties such as hardness. The developed mathematical model converted to a computer program. This program can be used independently or incorporated into a temperature history calculator to continuously calculate and display temperature history of the industrial quenched chromium steel bar and thereby calculate the mechanical properties. The developed program from the mathematical model has been verified and validated by comparing its temperature simulation results with commercial finite element software results. The comparison indicates reliability of the proposed model.

Abstract: The T122 steel (ferritic Fe-Cr-W alloy) and 347HFG stainless steel (austenitic Fe-Cr-Ni alloy) were corroded in the Na₂SO₄ salt at 800 and at 900 °C, and their hot corrosion behavior was studied. They displayed good corrosion resistance owing to the formation of the protective Fe₃O₄ and (Fe_0.6Cr_0.4)₂O₃ scales. These oxides effectively suppressed sulfidation by the Na₂SO₄ salt. The oxide scales that formed were thin and loosely adherent. The displayed good corrosion resistance was mainly attributed to the large amount of Cr in the alloys.

Abstract: Aeronautical thin-wall components are widely used in Aero-Engine, and the machining stability of the thin-wall components is a difficulty issue. In this paper, a single freedom dynamic model is set up to describe the dynamics of thin-wall milling process, and the stability of the dynamic model is analyzed with the discretization method. Then the modal parameters are gained in the different milling phases and the resonance region of spindle speed is proposed. Optimize the milling parameters with the chatter stability domain at different milling phases. The result shows that the cutting chatter can be restrained if getting the spindle speedcutting depth parameters considering the superposition area of chatter stability domains and avoiding the resonance region in the different milling phases. At last, the method is applied in Aero-Engine thin-wall blade milling, the metal remove rate increases greatly and the machining accuracy is improved greatly.

Abstract: The orthogonal experiment is processed for high-speed milling superalloy GH4169 with TiAlN coated carbide inserts. The empirical formula of the surface roughness is acquired by using Genetic Algorithm method. On the basis of this formula, studying the absolute sensitivity and relative sensitivity of surface roughness for milling speed, depth of cut and feed; The results showed that in the process of high-speed milling of high-temperature alloy GH4169, Surface roughness is most sensitive to the change of milling feed; change of milling depth take second place and milling speed is the least sensitive.

Abstract: In this paper, a frontal crash analysis is carried out with a full vehicle model in order to investigate the influence of stamping effects of auto-body members on the crash characteristics of the vehicle. Stamping effects are considered for load carrying members such as the front side member and the rear lower. From the analysis result considering stamping effects, it is conformed that stamping history has to be considered for longitudinal members simultaneously that transfer the impact load under the frontal impact. Comparison of simulation result with experimental one also shows that the prediction accuracy of the crash analysis is remarkably improved.

Abstract: The article developed a five-lump kinetic model for delayed coking through needle coke. The kinetic parameters were determined using the experimental results of the genetic algorithm method. The results showed the calculated concentration distribution agreed well with the experimental results. The results of five-lump kinetic model that composed of parallel and serial reactions and their activation energy also showed that the thermal sensitivity of coal tar pitch declined and that the orderly orientation strengthened under external magnetic field. This facilitates the formation of wide mesophase pitch structures in thermal conversion.

Abstract: Engineering ceramics have been extensively used as structural materials in modern manufacturing industries due to their excellent properties. High Efficiency Deep Grinding (HEDG) with Electrolytic In-process Dressing (ELID) process can realize the stabilized and controlled grinding process of engineering ceramics, but there lies many questions to be done. In the light of Y-TZP materials, the grinding process of HEDG with ELID was optimized, and comparisons were made between HEDG with ELID and HEDG without ELID process for Y-TZP ceramics, and mechanisms of HEDG with ELID were revealed.