Advanced Materials Research Vols. 97-101

Abstract: The microstructure and properties of aging at room temperature of dual phase steel produced by continuous annealing were investigated by using mechanical property test, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). In order to know the mechanisms of aging of dual phase steel produced by this process, the relative theories of dissolution and diffusion of interstitials, dislocation and precipitation are proposed and discussed. From analysis, the results showed that dual phase steel produced by continuous annealing had high strain aging resistance after overaging.

Abstract: Thermo-simulation test, transmission electron microscopy(TEM) and nanobeam EDS technique were used to investigate the strain induced precipitation behavior during relaxation process after deformed austenite in Mn-Mo-Nb-B low carbon multi-microalloyed Steel. The experiment results indicate that during isothermal held at 850 °Cand 900 °C after predeformation, the size of precipitates occurred in the Mn-Mo-Nb-B steel at different stage is smaller than that happened in the only Nb and Ti-bearing microalloyed steel. The ratio of Nb/Ti to precipitates increased with the relaxing time. After being held longer, Mo atoms would enter the lattice of (Nb,Ti)(C,N) precipitates and the amount in the precipitates increased with the relaxation as time prolonged.

Abstract: The effects of extrusion ratios (15, 30, 45and 60) on microstructure and mechanical properties of ZK60 magnesium alloy after T5 treatment were investigated. The results show that mechanical properties increase with the increase of extrusion ratios from 15 to 45．However, when the extrusion ratio is increase to 60, each mechanical property is decreased severly．By comparison，in the extrusion ratio of 30, ZK60 magnesium alloy after T5 treatment has excellent comprehensive mechanical properties．Different degrees of dynamic recrystallization appeared in the extrusion process and induced precipitation of second phase．The precipitation of the second phase is beneficial to the grain refinement and meanwhile to the promotion of the strength．

Abstract: This paper builds drive system model of belt conveyor during three kinds of stop process based on AMESim, and deduces belt tension equations. A case study on a long belt conveyor dynamic performance concludes that the braking stop process is shortest and motor stop process is longest. Also, the torque change rules of drive pulley among three kinds of stop process are same, that is increase at the beginning and decrease at last. The displacement of gravity take-up is largest during motor stop process, and the gravity moves far from the original point during power-off stop process.

Abstract: In this paper, experimental procedures are developed to measure the tensile mechanical property of ultra thin Copper (Cu) wire (=1mil) before and after electric flame-off (EFO). Characteristics of free air ball (FAB), heat affected zone (HAZ) and as-drawn wire on 99.99% Cu wire have been carefully investigated by nanoindentation, microhardness and self-design pull test fixture, respectively. A secondary EFO technique has been conducted to reduce the strength of Cu wire and increase the bondability. The determined accurate material properties can then be applied to finite element analysis (FEA) for further reliability studies. A series of comprehensive parametric studies were conducted in this research.

Abstract: The influence of rare earth Y addition and ageing treatment on the properties and precipitation morphology of Cu-Cr-Ti alloy was investigated. The results show that 0.1wt%Y addition increases the hardness, and decreases the electrical conductivity slightly. However, both the hardness and electrical conductivity decrease with an excessive Y addition. After ageing at 550°C for 2h, Cu-0.3Cr-0.2Ti-0.1Y alloy has a good combination of the hardness and electrical conductivity, which has the hardness of 134HV and the electrical conductivity of 73.9%IACS. After ageing treatment, most Cr rich phases precipitate in the form of sphere shape while a small amount of Cr rich phases exist in the form of acicular, and Y rich phases precipitate in the form of flake along the grain boundary.

Abstract: Transparent and conductive Al-doped ZnO (AZO) films were prepared by nonreactive DC magnetron sputtering with rapid thermal annealing process. The effects of sputtering power and annealing temperature on growth behavior, electrical rand optical properties of AZO films were investigated. The experimental results show that the sputtering power and annealing temperature had great influence on the electrical resistivity of AZO films due to the change of (002) orientation and grain size. The lowest electrical resistivity of AZO films was 5.3×10-4Ω•cm when the sputtering power was 100W and the annealing temperature was 200°C or above. The sputtering power and annealing temperature had little effect on optical transmittance, which was between 86% and 90%, but the absorption edge had a blue shift with the increase of sputtering power and annealing temperature.

Abstract: The growth of a crack in a bi-materials base under a building will cause the structure failure. The mechanism of this kind crack growth must be investigated. In this paper, a series of I-II mixed mode crack fracture experiments for bi-materials have been conducted. In some situations, a crack can grow from the weak medium concrete into the hard medium marble under compression load. The stress intensity factors KI ,KII and the first principle stress σ1 near crack tips have been calculated. The difference in crack propagation ability between the single-material and the bi-materials specimens are also studied. The experimental results are in accordance with the σθmax fracture criterion.

Abstract: A modified criterion γ’ (=Tx/(1.5Tg+Tl) of glass-forming ability (GFA) for metallic glasses is suggested on the basis of present criterion γ (=Tx/(Tg+Tl) that correlates well with some systems including metallic glasses, some glassy oxides and some cryo-protective aqueous solutions. Results show that the modified criterion γ’ shows stronger correlation with the critical cooling rate Rc for metallic glasses than the criterion γ, which is demonstrated by a value increase in the statistical correlation parameter R2 from 0.9022 to 0.9037. Furthermore, a modified equation is given to reflect the relationship between γ’ and Rc.

Abstract: Asymmetrical conditions that occur during plate rolling can cause front end bending or lead to poor product shape, profile, quality and cause reduced productivity. In these investigations, a model of calculating curvature is deduced according to the theory of rolling, which has been used to determine the effect of surface friction mismatch on the direction and severity of curvature in plate rolling. Results show that the front end bending can occur easily due to the mismatch of coefficient of friction. Moreover, the results have identified that the bending inclination of large reduction, large radius of roll and thin rolling stock is higher than that of the reverse, the bending inclination of the entrance thickness of rolling stock is higher than that of the reduction, and the bending inclination of the reduction is higher than that of the radius of roll.