Advanced Materials Research Vols. 1120-1121

Abstract: Electromagnetic micro-punching is a novel micro-punching process in which metal foil occur plastic deformation until shear fracture under magnetic impact load. In this paper, electromagnetic micro-punching process was investigated on T2 copper foil. Effects of discharge energy, foil thickness and discharging time on micro punching were discussed. The results show that micro holes were successfully pierced with the discharge energy more than 5.0 kJ on copper foil of 20 μm in thickness. Foil thickness is the main factor in electromagnetic micro-punching with the discharging energy of 7.2 kJ. In addition, increasing discharging time can punch micro hole on thicker foil. The micro holes with diameter of 0.4-1.4 mm were successfully punched on 20 μm copper foil in thickness with discharge energy of 7.2 kJ.

Abstract: Material cutting properties can be judged by turning temperature and chip shape. A new method that can measure turning temperature more accurately was discussed in this paper. Compared with the traditional method, results show that turning temperature can be accurately measured through a new method in turning process. Turning temperature become stable and will not jump after 20s later. In addition, the higher the hardness, the higher the energy is needed, leading to the higher turning temperature. The average turning temperature of the quenched specimen, normalized specimen and annealed specimen measured through the new method is 100°C,70°Cand 60°C, respectively. And the chip morphologies of quenched specimen, normalized specimen and annealed specimen are irregular band chips, spiral debris chips and C-shaped chips, respectively.

Abstract: In the paper the methods of designing and manufacturing of the metals foam with regular cells are researched. The software models of metals foam are designed by CAD. The models are transmitted into 3D printing machine to manufacture foam framework. The metal foams with regular cells and fixed porosities are manufactured by chemical plating, electric plating and investment cast. According to the applications the structures of metal foams can be designed to control sizes, shapes and distribution of pores, porosities, density and to control the properties of metals foam, which can satisfy various demands of applications. Nickel foam with regular cells is designed and manufactured by this method.

Abstract: This paper aims to study the sintering process and mechanical properties of submicron polycrystalline diamond (SMPD) without any secondary phases and binder materials under pressure of 7-8 GPa and 1400 °C-1800 °C, using the bi-layer assembly and the conventional assembly methods. The as prepared samples were characterized by X-ray diffraction, scanning electron microscope, and Vickers indenter hardness tests. Well sintered specimen was obtained under the condition of 8 GPa and 1600 °C using the bi-layer assembly method, and an indentation test demonstrated a Vickers hardness of 52 GPa. The graphitization of diamond was found to be an important factor determining the hardness of samples sintered using the bi-layer assembly.

Abstract: In this paper, using orthogonal design method, considering the extrusion temperature, extrusion speed, extrusion billet, die structure, which will affect the uniformity of the metal flow[1]. Using the outlet velocity average standard deviation, the average pressure and the mean maximum equivalent stress as the criterion, select the optimal process scheme of two-hole dies aluminum profile extrusion. And the optimal scheme is validated by simulation and, the results show that the extrusion velocity is uniform, no forming defects, it can stably forming. At the same time, the experiment provides theoretical guidance for real extrusion production with multi-hole dies.

Abstract: The grinding process requires a high energy expenditure per unit volume of material removed. The high temperature generated in abrasive processes is the main factor responsible for thermal damage to a ground surface. An investigation was undertaken to explore the temperature characteristics in high speed grinding (HSG) of silicon carbide (SiC) with a vitrified diamond wheel. A grindable thermocouople technique including a NI-DAQ device will be used to measure the grinding temperature. This paper will discuss the temperature characteristics in high speed grinding of SiC in detail and give an experiment-based temperature distribution model for SiC. A molecular dynamics simulation will be used to illustrate the effect of a high loading rate on SiC material’s mechanical property, which will further elaborate its unique HSG temperature characteristics. The experimental investigation will provide more practical application support in utilizing HSG technology in a high quality ceramic grinding.

Abstract: Wear resistance of tool steels can be increased with deep cryogenic treatment (DCT) application. Mechanisms related to DCT are still not completely understood. Microabrasive wear resistance of cryogenically treated samples of AISI D2 steel was evaluated in terms of austenitization temperature at heat treatment cycle and quenching steps related to DCT. X-ray difractometry, scanning and optical microscopy and quantitative evaluation of carbides with image analysis were carried out aiming material characterization. For samples subjected to higher austenitization temperatures, the DCT treatment does not increase abrasive wear resistance. For samples treated at lower austenitization temperature, the DCT treatment results on 44% increase at abrasive resistance. This effect is correlated to the increase of the amount of fine carbides distributed at samples matrices cryogenically treated.

Abstract: The existing process of 2A12 aluminium alloy piston is cutting completed by hot- drawing pole , as a material utilization rate less than 40%. In order to improve material utilization, cold-extrusion process is the reasonable choice, but only if solve the annealing before cold-extrusion, surface lubricated, the Parameter optimization of cold-extrusion and quenching process after extrusion. This research uses the DEFORM finite element analysis and a good effect in practical application is obtained to enhance the rate of more than 80% material utilization, scrap rate is less than 0.5%.

Abstract: The article presents the results of selective laser melting of Ti-6Al-4V alloy. It was studied phase composition and microstructure of the initial powder material, the specimens manufactured by Selective Laser Melting and also the specimens after heat treatment. The effect of heat treatment on microstructure and mechanical properties of the specimens was shown. It was studied the mechanical behavior of the manufactured specimens before and after heat treatment at room and elevated temperatures as well. After heat treatment tests showed that the specimens have decent mechanical properties both at room and elevated temperatures.

Abstract: In order to eliminating the banded structure in SAE8620H gear steel,an isothermal annealing process and its mechanism has been studied in this paper. Results showed that isothermal annealing process can effectively eliminate banded structure in SAE8620H gear steel.With isothermal temperature 640°C-a certain low temperature indeed high undercooling,and for high nucleation at this temperature resulting in the decrease of nucleation rate difference in all areas,banded structure level decreased to 1 level.When isothermal temperature decreased to 610°C and 590°C,although the undercooling is so high that various regions began to nucleate at the same time,the transition temperature is so low that alloy elements in the regions previously occupied by pearlite bands diffuse faster than other regions,thus proeutectoid ferrite grains in these regions grow faster,regenerating the banded structure .