Advanced Materials Research Vols. 1120-1121

Abstract: This research paper deals with assess effect amount of recycled material on Charpy impact behavior. Valuation of recycled material effect takes place on four kinds of thermoplastic materials, high-heat polycarbonate is always mixture with different amount of recycled material (pure polycarbonate, polycarbonate with 20 percent of recycled material, polycarbonate with 30 percent of recycled material and pure recycled polycarbonate). Specimens were prepared by the mostly used technology for production products, which is injection molding. Each kind of material is one by one loaded by different temperatures; at reduced, and three increased temperatures and consequently tested. To determine influence of recycled material was used Charpy impact test.

Abstract: Radiation crosslinking of linear polyethylene (LLDPE) is a well-recognized modification of improving basic material characteristics. This research paper deals with the utilization of electron beam irradiated LLDPE on the micro-indentation test. The effect of the irradiation on mechanical behavior of the tested polyethylene was investigated. The results indicate that the mechanical behavior, highly depends on the intensity of irradiation. Toughness and hardness grew with increasing dose of the irradiation LLDPE. Indentation modulus increased from 0.25 to 0.28 GPa and indentation hardness increased from 21.89 to 26.25 MPa. These results indicate advantage crosslinking of the improved mechanical properties.

Abstract: Cross-linking is a process in which polymer chains are associated through chemical bonds. This research paper deals with the possible utilization of irradiated polyamide. Influence of the intensity of irradiation on micro-indentation hardness was investigated. Material properties created by β – radiation are measured by micro-indentation test using the DSI method (Depth Sensing Indentation). Hardness increased with increasing dose of irradiation at everything samples; however results of micro-indentation test shows increasing in micro-mechanical properties of surface layer. The highest values of micro-mechanical properties were reached radiation dose of 99 kGy, when the micro-mechanical values increased by about 18%.

Abstract: Radiation processing of polymers is a well-established and economical commercial method of precisely modifying the properties of polymers, especially thermo-mechanical properties. The tensile behaviour of modified HDPE samples by radiation cross-linking was measured at the ambient temperature and after temperature load at 220 °C. The tested samples showed significant changes of thermo-mechanical properties and tensile behaviour after 220 °C. From this point of view, new applications could also be seen in areas with service temperatures higher than their former melting point.

Abstract: In the present study, we present a novel method to sinter Cr₃C₂ powders under high pressure without any addittives. The sintering Cr₃C₂ samples were charaterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), relative density measurements, Vicker’s hardness tests and Fracture toughness tests. The reasults show that Cr₃C₂ powders could be sintered to be bulk under the conditions of 3-5 GPa, 800-1200 °C and the heat preservation for 15 min. Moreover, the sintering body of Cr₃C₂ compound with the relative density of 99.84% by simultaneously tuning the pressure-temperature conditions exhibited excellent mechanical properties: a Vickers hardness of 20.3 GPa and a fracture toughness of ~8.9 MPam^1/2. These properties were much higher than that by using the previous methods. The temperature condition obtained good mechanical properties in the experiment was about 1/3 lower than that using any other methods owing to the high pressure.

Abstract: Injection molding is one of the most extended polymer processing technologies. It enables the manufacture of final products, which do not require any further operations. The tools used for their production – the injection molds – are very complicated assemblies that are made using several technologies and materials. Delivery of polymer melts into the mold cavity is the most important stage of the injection molding process. The fluidity of polymers is affected by many parameters Inc. mold design. Evaluation of set of data obtained by experiments in which the testing conditions were widely changed shows that the quality of cavity surface and technological parameters (injection rate, injection pressure and gate size) has substantial influence on the length of flow.

Abstract: The process of radiation crosslinking helps to improve some mechanical properties of polymer materials. Micromechanical changes in the surface layer of Thermoplastic elastomer (TPE-E) modified by beta radiation were measured by instrumented test of microhardness. The specimens were prepared by injection technology and subjected to radiation doses of 0, 66, 99, 132 kGy. Measurements of microhardness showed considerable changes of behavior of surface layer in middle as well as high radiation doses with higher values of indentation hardness and stiffness.

Abstract: The law and mechanism of hydrogen induced softening in Ti6Al4V alloy in the temperature range 400 °C to 1010 °C are researched by lots of isothermal hot compression experiment in this paper. The relationship between σ_h (the true stress when the test is compressed to half of its original height) and C_H (hydrogen content) is investigated to describe the law. The results show that, Between 400 °C and 450 °C, the plasticity increases at first, and then decreases and the strength is almost changeless with the C_H rising. Between 480 °C and 950 °C, the strength decreases at first, and then increases with the C_H rising. In α+β phase region, the strength decreases with the C_H rising. In β phase region, the strength increases with the C_H rising. Hydrogenation induced α phase high temperature softening and hydrogenation promoting α→β phase transition are the main reasons for hydrogen induced titanium alloy softening. Hydrogenation induced β phase solution strengthening is the reason for hydrogen induced titanium alloy strengthening. And the relationship between furnace temperature and vacuum is investigated during dehydrogenation heat treatment.

Abstract: Aluminum brass possesses an attractive combination of properties including high strength, high thermal and electrical conductivity, good mechanical workability, excellent corrosion resistance, low susceptibility to stress corrosion cracking. This make it a preferred choice for bimetal strips. The materials for preparing bimetal strips with cold roll bonding should have a good plasticity. In the present work, a Cu-Zn-Al-Ni alloy was proposed and the annealing process for this aluminium brass alloy was studied. The effect of annealing temperature and annealing time on the microstructure and mechanical properties was investigated. The proper annealing parameters were obtained.

Abstract: Hydrogen as the main cause of the gas porosity in aluminium alloys should be removed before casting. The degassing process with intensive melt shearing shows a high efficiency. In the present work, the water simulation was used to study the high shear degassing process and the effect of rotation speed on the size and distribution of inert gas bubbles. The results show that with the increase of rotation speed, the bubble size decreases and the affected region becomes larger. The proper rotation speed of the rotor for the rotor-stator high shear degassing process is 5000-6000 RPM.