Advanced Materials Research Vol. 421

Abstract: Hot stamping has become the main technology to produce complex-shaped high-strength steel components. However, hot sheet metal forming can cause high rates of die wear and the scratching of the productions. A hot drawing tribo-simulator was designed to investigate the friction and wear behavior of high strength steel at elevate temperature. The value of the friction coefficient was obtained to examine the function of the tribo-simulator. The results prove that the coefficient of friction in hot stamping can be measured using this tribo-simulator. Moreover, the coefficient of friction is able to be used in finite element simulation to improve the accuracy of the modeling results and it is also an important indicator to evaluate the tribological behavior between the die and sheet metal.

Abstract: The melting curve is an important thermodynamic property in studies of solid-liquid phase transitions. It can be calculated via molecular dynamics simulations. We simulated the melting process of pure Al with three methods, the heat-until-it-melts (HUM) method, the two-phase method and the hysteresis method. The results calculated via HUM method is approximately 20% higher than experiment data while the results calculated via two-phase method and hysteresis method are in good agreement with experiment data.

Abstract: On the basis of fire hazard simulation study of aluminum cable joint, it reveals that large contact resistance at cable joint can induce high temperature, and easily ignite combustibles then catch fire. Through macro-examination and metallographic analysis about the melted marks of aluminum cable joint, it clarifies the formation mechanism of the melted marks, and the corresponding preventive measures which can prevent cable fires, provide a practical and reliable scientific basis to guarantee the safe operation of power system.

Abstract: This study aims to investigate the effects of mechanical melt-shearing treatment during casting process on the morphological change of iron-containing intermetallic phases formed in the high-iron bearing Al-Si casting alloys. The process parameters of the melt-shearing treatment were controlled and optimized in order to modify the needle-like shape of the iron-containing intermetallic into a less harmful form. Throughout this study, it was found that the melt-shearing treatment shortened effectively the length of the needle-shaped iron-containing intermetallic phase in the Al-Si alloys. It was also confirmed that these modified morphology and microstructures result in the improvement of mechanical properties.

Abstract: The temperature field of hot strip during rolling was simulated by FEM. The temperature drop curve and temperature field at any time were solved Furthermore, a temperature field simulation software based on the practical production conditions was developed and applied to simulate the temperature field of a combination of multiple grades of steel, rolling, diversified equipment and cooling steps. In the end, simulation results are analyzed and edge masking controlling in width in LFC is discussed.

Abstract: In this paper analytical predictions of the molten region around the cavity produced by a moving electron beam are provided. A three-dimensional analytical model is used to predict the molten and heat-affected regions surrounding a paraboloid of revolution-shaped cavity. This work avoids the defect of the infinite temperature at the cavity base for the line-source model. Introducing a new image method, an analytical solution is provided by satisfying exactly the adiabatic condition at the top surface. The molten region is governed by dimensionless parameters related to beam power per unit penetration and the depth and shape of the cavity in this work. A three-dimensional molten region is computed and presented in this paper. The effect of beam power per unit penetration on the molten region is also discussed.

Abstract: A novel porous CuAlMn shape memory alloy (SMA) has been successfully fabricated by sintering-dissolution process. Effect of solution treatment on the microstructure and the reverse martensitic transformation (MT) behavior of the resulting specimens are investigated by means of SEM, optical microscope, DSC and internal friction (IF). The results show that with increasing solution temperature, the content and the size as well as the arrangement order of martensite in matrix increase. The reverse MT behavior follows different dependences on solution temperature and solution time at different temperature ranges. The related mechanisms are discussed in terms of the changes of the content of martensite and the concentration of quenched-in vacancies.

Abstract: The minimum mould exit shell thickness (MEST) is one of key factors to consider for continuous casting machine design and the strand cooling schemes. Based on the shell strength at elevated temperatures, a concept of shell integral average strength, from its very top surface to the solidus frontier, has been introduced to judge its bulging tendency under ferrostatic pressure. Considering the contribution to the shell stability, a mathematic model for the determination of the minimum MEST has been brought forward. It is shown that, the minimum MEST of the round bloom is decided by not only the cross section and the minimum roller spacing, but also the opening degree of the support roller and the support roller on the side. Taking a round bloom casting of plain carbon steel (grade Q235) as an example, there is the cross point with the curve of the minimum MEST by the minimum roller spacing and the minimum MEST by the fluting include angle of the support roller and the support roller on the side against the cross section, if its own geometry structure cannot hold the ferrostatic pressure, the minimum MEST on the left of the cross point can remain as the determined amount by the minimum roller spacing; but on the right, it is increased with the increasing width of cross section.

Abstract: In this paper, residual stress modeling using the finite element (FE) method is presented. The heat source is represented by the Goldak’s double-ellipsoid model. The Koistinen–Marburger relationship was employed here in order to trace the martensite fraction in the material during martensitie transformation in residual stress analysis. The relationship between stresses and martensite fraction are presented. Stress distribution is affected by matensite transformation.

Abstract: The p-n junction film which consists of the conductive polymer of p type semiconductor of polyhexylthiophene (PAT-6) and n type one polyquinoline(PQ) was fabricated by self-assembly by applying novel stratified phase separation phenomenon that had been discovered previously by us. The film showed ideal characteristic I-V relationship of the diode device