ZHAO Ping, HE Qing-hua, LI Wei, LU Bo. Mechanism of Fatigue and Creep and Fatigue-creep of DD3 Single Crystal Superalloy at Elevated Temperature[J]. Journal of Materials Engineering, 2010, 0(8): 1-4.
Mechanism of fatigue and creep and fatigue-creep of DD3 single crystal was investigated at different temperature with different stress levels along different orientations.The results show that DD3 single crystal has obviously anisotropic for the fatigue and creep and fatigue-creep properties, is the highest, takes second place and is the lowest.The effect of orientation on fatigue is higher than creep and fatigue-creep.DD3 single crystal has good creep properties and relatively weak fatigue properties,creep is primal in fatigue-creep.
LIU Kun-peng, YOU Yi-liang, ZHANG Shan, ZHANG Zheng. Fracture Analysis of 50CrVA Torsion Bar[J]. Journal of Materials Engineering, 2010, 0(8): 5-7,11.
The fracture reason of the fractured torsion bar of 50CrVA was analyzed by fracture surface observation,metallurgical structure observation,hardness test and fatigue strength checking.The result of fatigue strength checking showed that the fracture was mainly caused by higher torsion load.Large-dimension inclusions richly containing Zn in the torsion bar accelerated the crack initiation and shortened fatigue life of the torsion bar.
JIANG Da-chuan, DONG Wei, TAN Yi, WANG Qiang, PENG Xu, LI Guo-bin. Investigation on Removal of Aluminum Impurity in Metallurgical Grade Silicon by Electron Beam Melting[J]. Journal of Materials Engineering, 2010, 0(8): 8-11.
Aluminum impurity with high vapor pressure in metallurgical grade silicon was removed effectively by electron beam melting.Comparing the calculated value and the measure evaporation loss,the mechanism of aluminum evaporation through the surface of the molten silicon can be assumed that the removal rate-limiting step of aluminum impurity in silicon is diffusion step.In addition,the relationship between the removal amount of the aluminum and silicon loss is also discussed.
WU Xiang-kun, ZHOU Xiang-lin, WANG Jian-guo, ZHANG Ji-shan. Numerical Investigation on Acceleration of Gaseous Mixture of Nitrogen and Helium on Particles During Cold Spraying[J]. Journal of Materials Engineering, 2010, 0(8): 12-15.
The acceleration of the gaseous mixture of nitrogen and helium on particles in the de-Laval nozzle was analyzed using FLUENT software,and numerical results of gas flow were compared with one-dimensional steady isentropic theoretically ones.Moreover,the effects of the helium content of gaseous mixture on the gas and particles velocity and temperature in the nozzle exit were studied.The results show that the numerical values are similar to the theoretical ones,therefore numerical simulation can be expected to determine the process parameters to guide the cold spraying process.In additional,with the helium content in the gaseous mixture increasing,the gas and particles velocity increase,but temperature is lower,however,the rate of change of velocity and temperature decrease.When nitrogen with a small amount of helium gas is used as acceleration gas,particles velocity in the nozzle exit increases while the consumption of helium is reduced.
WANG Yan, LEI Yong-ping, FU Han-guang, LIN Jian. Study on Electrodeposition of Low-stress Ni-Co Alloy Coating in Sulfate Bath[J]. Journal of Materials Engineering, 2010, 0(8): 16-19.
Low-stress Ni-Co alloy coatings were obtained in sulfate bath by adding proper amount of butynediol and saccharin.The effect of butynediol and saccharin concentration on cross-section morphology,microhardness,structure and internal stress of the coating was investigated.The results showed that butynediol and saccharin could lead to finer grain,higher microhardness and stronger(111) plane.Butynediol could produce the coating contraction and tensile stress,while saccharin could produce the coating expansion and compressive stress.The coating internal stress range from 64.64MPa to-3.5MPa by adding 0.08g/L butynediol and 2g/L saccharin to the sulfate bath,and the coating had high microhardness and quality.
WANG Xue-hua, CHEN Gui, LI Cheng-yong, YANG Liang, CAO Hong, ZHOU Wei-min. AC Electrochemical Deposition of Cu Nanowire Arrays and Its Mechanism[J]. Journal of Materials Engineering, 2010, 0(8): 20-23.
Cu nanowire arrays were prepared by alternating current(AC) electrochemical deposition method in anodic aluminum oxide(AAO) templates with highly ordered pores processed by secondary anodic oxidation.The morphology and structure of Cu nanowires were characterized by SEM,TEM and XRD,respectively.The results indicated that Cu nanowires preferred orientation along(Ⅲ) had uniform distribution in Cu/AAO nano-composite thin films.The Cu nanowires had a structure of parallel bright stripes alternating with parallel dark stripes.The mechanics of ac-electro-deposition was discussed.
NIE Xiang-hui, LI Yun-long, LI Ji-ke, ZHANG Hong-bo. Morphology,Products and Corrosion Mechanism Analysis of Q235 Carbon Steel in Sea-shore Salty Soil[J]. Journal of Materials Engineering, 2010, 0(8): 24-28,33.
Macroscopic and microscopic morphologies of Q235 carbon steel corrosion in sea-shore salty soil with different water contents were observed,corrosion mass losses were calculated,and the corrosion products were analyzed by Raman spectra.The duration of corrosion was a month,and the water content of the soil was 10%,20% and 34% respectively.Being controlled by diffusion process,the mass loss of Q235 carbon steel in 10% water content soil was biggest,and the morphology was mainly local corrosion.The mass loss decreased with the increasing of the water content,and the morphology turned to general corrosion.The corrosion products of 20% and 34% water contents were mainly α-FeOOH.Under the effect of dehydration,there were two layers of corrosion products for 10% water content,the inner was α-FeOOH,and the outer was mainly Fe2O3 and Fe3O4.
WANG Li-jun, CAI Qing-wu, YU Wei, WU Hui-bin, LEI Ai-di. Characterization and Formation Mechanism of Microstructures of Low Carbon Low Alloy Steel During Continuous Cooling Transformation[J]. Journal of Materials Engineering, 2010, 0(8): 29-33.
The static continuous cooling transformation curves of low carbon low alloy steel contained with elements of Mn,Ni,Mo,Cr,V and Ti et al were determined by Formaster-Digital dilatometer.The effect of cooling rate on microstructure evolution was investigated by optical microscope,transmission electron microscopy(TEM)and micro-hardness measurement.The results show that microstructures of tested steel include polygonal ferrite(PF) and pearlite(P) after phase transition at the cooling rate of 0.03℃/s.The degenerated pearlite(PD) and acicular ferrite(AF) appear at the cooling rate of 0.06℃/s and 0.29℃/s,respectively.The microstructures contain granular bainite(GB) and lath bainite(LB) at the cooling rate of 1.7℃/s.The martensite(M) are observed at the cooling rate of 42℃/s.It’s proposed that the occurrence of degenerated pearlite in the low carbon steel at extremely slow cooling rate is attributed to the coupling interaction of mult-componet in the low alloy which resulted in change of activity of the carbon.Intragranular nucleation and growth of acicular ferrite play a role of segmentation to the subsequent phase transition microstructure,which is benificial to grain refinement.Segregation of alloy with hardenability causes large shear stress during transformation and lead to the formation of local twin-martensite in the low carbon steel.
