Papers by Keyword: High Temperature Property

Abstract: Friction stir welding (FSW) is a solid state joining process in which metals are joined together using frictional heat and severe plastic deformation. The heating and the mixing of the metals is performed using a hardened tool with a shoulder and pin. FSW of lightweight metal alloy Al6061 has been carried out in the present study. For welding aluminum the parameters used were a constant tool rotation speed of 1600 rpm and varying tool translation speeds of 250, 500, 750 and 1000 mm/min. The welded coupons were characterized for microstructural observations and mechanical properties such as tensile and Charpy impact properties. The tensile and impact properties were studied at two different temperature namely, room temperature (RT) and 300°C. The FS welded aluminum specimens showed 86% – 98% tensile yield strength, in comparison to the base material at RT. At 300°C, the yield strength was observed to be 85% to 93% of the base material value. For the impact properties, the Al specimens showed 60% – 140% specific impact energy, in comparison to their respective base materials. Based on the mechanical properties and microstructural examination, the optimal weld parameter was identified as 1600 rpm and 250 mm/min which is dependent on the tool pin and shoulder design utilized in the study.

Abstract: In this study, mullite was used as the addition to prepare silicon based ceramic cores, and the effect of mullite content on the mechanical and chemical properties was investigated. The phase composition and the morphology of the ceramic cores were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The results indicated that the shrinkage was induced by the addition of mullite and contaminations. The intensity of pre-heated cristobalite increased sharply with the mullite content increasing, which could improve the high temperature deformation simultaneously. However, mullite was difficult to remove by reacting with KOH which decreased the leaching rate of ceramic core. When mullite content was 15 wt%, the shrinkage of ceramic core was 0.78%, the creep at 1540 °C for 1 h was 0.3 mm and the leaching rate was 0.1 g/min, which meets the need of ceramic core of hollow turbine blades.

Abstract: Rutting test, residual stability test and freeze-thaw split test were used to measure the properties of asphalt mixture with different graduation and same mixing amount of fibers, the results were analyzed to obtain the influence of graduation types in the road performance of fiber-reinforced asphalt mixture. The results showed as follows: fibers could obvious improve the high temperature property and water stability of asphalt mixture; the graduation types have visible impact on the improvement of all properties of fibers-reinforced asphalt mixture; SMA-13 has the greatest influence in improving the performance of fibers-reinforced mixture; the improving effect of dense graduation AC mixture will gradually decrease when the nominal maximum aggregate size was becoming bigger; graduation optimization design should be used in mix design of fibers-reinforced mixture to enhance its road performance.

Abstract: According to the requirement of the pot scaleboard of Coke Dry Quenching, high content of aluminium heat resisting alloy was developed.Through changing the content of carbon,boron and titanium,the best compounding of the heat resisting alloy was Fe-8Al-1B-5Cr-0.3C-0.5Ti.The microstructure of this kind of alloy was observed and analyzed with optical microscope.It also had good performance of oxidation resistance,abrasion resistance and thermal fatigue resistance,it was suitable for using as pot scaleboard of CDQ.

Abstract: This report mainly evaluated the pavement performance of natural asphalt from Albania. Firstly, base asphalts were processed with natural asphalt by “wet method” modification technique to obtain modified asphalt; and mixture are produced with these modified asphalt binders, and then high temperature performance and moisture stability properties are evaluated by some standard methods. Analysis shows that this natural asphalt can remarkably improve the high temperature and moisture stabilities of asphalt mixture, and own cost-effective advantage.

Abstract: To refine thick and brittle needle-like or sheet-like iron-rich phase in Al-Fe-based alloy, electromagnetic cast and solid extrusion were adopted for the preparation of billet of rolled alloy Al-5%Fe-1.2%Si-1%Mg-0.6%Cu-0.5%Mn. Studies were made of the effect of rolling process on the microstructure and mechanical properties especially on the mechanical properties at high temperature. The hot deformation behavior of Al-Fe alloy was simulated at the strain rate of 0.01s-1 to 10s-1 and the temperature between 783K and 693K. The results indicate that there is significant steady-state rheological feature on the alloy’s high temperature deformation and the flow stress is sensitive to strain rate and temperature. The tensile strength of the alloy can reach 348MPa at 150°C and 170 MPa at 300°C but with a drop of around 40% than that at room temperature, indicating that heat resistance of the alloy is better at 150-200°C, the strength simulated long at 80°C can reach 275MPa, with rather good thermal stability.

Abstract: High-temperature properties of 10 samples of iron ore from Brazil, Australia and China were measured. Several conclusions were made based on these experimental results. Assimilability of Brazilian ore, Australian ore and Chinese ore concentrate were low, high and medium, respectively. Optimal fluidity of liquid phase was observed in 2 types of Brazilian ores (BR-B, BR-C), 1 type of Australian ore (AU-C) and 1 type of Chinese ore (CH-D). For self-strength of the bonding phase, Australian ore presented low levels, while Brazilian and Chinese ore presented high levels. According to the experimental results of high-temperature properties of iron ore, schemes of ore blending optimization were designed and sinter pot test using these blends were performed. The results indicated that ore blends composed of 30~45% Brazilian ores + 25~50% Australian ores + 20~30% Chinese concentrates presented excellent sintering results, considering both the performance of the processing and quality of the sinter. Therefore this experiment has proved that ore blending optimization combining high temperature properties can lead to more efficient sintering mixes.

Abstract: Metallic fibers (Fe-Cr-Si) with an excellent high temperature strength are expected to be use as a reinforced material of the engine piston head. However, the high reactivity of Al with most metals has disturbed the use of metallic fibers in aluminum composites until now. In this study, the influence of the reaction products at the fiber/matrix interface on high temperature properties of the composites was investigated by different solution treatment conditions. It is found that hardness and strength increase with an increase the solution treatment temperature (Tst). Reaction products (Al-Fe intermetallic compounds) resulting from solution treatments were formed along the fiber/matrix interface at 773 K or higher. The composites without interfacial reaction products (Tst=763 K) showed excellent rotating-bending fatigue life at 573 K. The fatigue crack propagation in this composite occurred at the necking region of the metal fiber because no cracks were observed in the interfacial reaction products.