Advanced Materials Research Vol. 699

Abstract: Aluminum alloy welding wire ER5356 was welded on galvanized steel plate by Pulsed DE-MIG. The best welding seam morphology was got by adjusting Pulsed DE-MIG welding parameters. It indicated that welding-brazing of aluminum-galvanized steel dissimilar metals were achieved by Pulsed DE-MIG. SEM and EDS were adopted to observe and analyze the interface microstructure of welding joints. The results indicated that two intermetallic compounds layers of Fe2Al5 and FeAl3 formed along the interface of aluminum-steel. And models of interface reaction of aluminum-steel dissimilar metals were put forward.

Abstract: The surface of polypropylene hollow fiber membrane was modified with N,N’-methylene-bisac-rylamide (MBA) by the UV-irradiation, with the benzophenone (BP) as the light initiator. Fourier transform infrared spectrometer (FT-IR) was utilized to characterize copolymer composition. Field emission scanning electron microscopy (FE-SEM) was utilized to observe the fiber surface and section. Results showed that MBA was grafted on the surface of membrane. The influence was researched by changing the concentration of BP, MBA and irradiated time. Results showed that the grafting rate grew rapidly and then declined as the increase the BP concentration. The grafting rate increased at first as the MBA concentration increased, but decreased after the maximum. The grafting rate firstly increased slowly and then increased sharply with the irradiated time extended.

Abstract: Titanium dioxide (TiO₂ ) thin films have been deposited on glass substrates under various conditions by using a homemade reactive DC sputtering technique. The TiO2 has unique characteristics and economical alternative material for transparent conductivity oxide thin films compared with other materials. In this study, titanium (Ti) has been used as a target while argon (Ar) and oxygen (O22</subthin films has been measured by using a calibrated I-V meter. On the other hand, the transparency, microstructure and component of TiO2 thin films have been investigated respectively by using UV-VIS spectrophotometer, XRD and SEM (EDX). The thickness of TiO2 films, the grain size and the band gap have been also successfully estimated. As a result, the conductivity of films increased for Dt at 1 hour to 3.5 hours and decreased for Dt at 4 hours. It means that the optimum Dt was at about 3.5 hours. It may be related to the thickness (structures) of the films. In addition, the thickness and grain size increased by increasing Dt, while the band gap decreased when the film structure changed from non-crystalline structure to crystalizing structure.

Abstract: Greatbatch Medical, specializing in orthopedic implants and instruments, is currently utilizing direct metal laser sintering (DMLS) technology to develop concept prototypes. Greatbatch uses EOS GP1 Stainless Steel which adheres to the American standard for 17-4 Precipitation Hardened SS. Following DMLS, Greatbatch heat treats its parts to obtain desirable mechanical properties. In this study, three different heat treatment methods were examined: heat treatment and stress relief (HT+SR), stress relief (SR), and solution aging and annealing (SAA). The Vickers Hardness Test and the Tensile Strength Test were used to assess the mechanical properties of each sample. The research also included grain structure analysis using a Scanning Electron Microscope and surface roughness studies via profilometer measurements. For example, the HT+SR sample yielded 456 HV (hardness), an ultimate tensile strength of 1319 MPa, an yield strength of 1120 MPa, and 6.36% elongation. It was found that compared to the untreated sample, HT+SR decreased the total elongation by 73% and SAA decreased total elongation by 17% and additionally decreased hardness by 17%. It was learnt that stress relieving the part after DMLS was the superior method of choice based on its resulting mechanical properties. It was found that the grain structure of the non-treated sample resembled a solution treated sample and the stress-relieved sample actually matched an age-hardened sample. The sample that was precipitation hardened was actually over-aged. Thus it was found that the DMLS process seemed to be acting as an aging process while simultaneously building the part. Further studies in examining specific effects of DMLS and how it impacts what order heat treatments should follow would be appropriate.

Abstract: Aiming at the triple splitting rolling process of Φ14 mm ribbed bar in small section continuous rolling line, a nonlinear thermal-mechanical coupled finite element model was setup to investigate the splitting mechanism based on the normalized Cockroft-Latham criterion and algorithm of removing elements. From the simulation results, the exit cross section profile, stress and strain distribution of workpiece in each pass is presented. The metal separating in splitting pass and the cause of formation of the insufficient defect was discussed, and the prediction result is in good agreement with that of the practice in the steel company.

Abstract: The flow behavior and microstructural evolution of an as-wrought duplex stainless steel has been investigated by Gleeble-3500 thermal-mechanical simulator within the temperature range of 950-1200°C and the strain rate range of 0.1-10s-1. The flow curves exhibited a peak stress characteristic followed by dynamic softening and the strain for appearance of steady stress is bigger at higher strain rate than at lower strain rate. The apparent activation energy (Q) and the apparent stress exponent (n) of the test steel are obtained to be about 462 kj/mol and 3.95, respectively. The relationship between peak stress (σp) and Zener-Holomon parameter (Z) is obtained, whereby the σp can be predicted at differern hot working conditons. The results of microstructural observation show that the austenite softens by the dynamic recrystallization (DRX) which can be dominantly responsib le for dynamic softening, while the ferrite phase mainly continues to exhibit dynamic recovery (DRV).

Abstract: 3D Printing is one of the few powder-bed type rapid prototyping (RP) technologies, which allows fabrication of parts using powder materials. Understanding of mechanical properties of 3D parts made by this process is essential to explore more applications of this technology. In general, the mechanical properties of many RP produced parts depend on the process parameters andalso on post-processing methods of that RP process. Very few studies have been made to characterize the mechanical properties of 3D Printing processed parts. This paper presents an experimental investigation on how tensile properties of parts fabricated by 3D Printing is affected by 3D Printing build orientation, and by post-processing methods of infiltration process and drying of parts. Results obtained forvarious parameters are compared to investigate the optimum procedure to achieve the highest tensile strength using ZP150 powder material.

Abstract: In this paper, Ni-silicide formed by co-sputtering of Ni and Ti on a boron cluster (BF₂, B₁₈H₂₂) implanted ultra-shallow source/drain for MOSFET (metal oxide semiconductor field effect transistor) is proposed. Ni and Ti with a TiN capping layer were deposited by co-sputtering on boron cluster implanted wafer. By analysis of its sheet resistance, interfacial structures, surface morphological stability, and phase formation after post-silicidation annealing, thermal stability of Ni-silicide was found to be improved a lot.

Abstract: The palm fruit biomass is introduced into the pyrolysis reactor bed and the transport equations for heat, mass and momentum transfer are solved using computational fluid dynamics (CFD) technique. The Eulerian-Eulerian approach is employed to model fluidizing behavior of the sand for an externally heated reactor prior to the introduction of the biomass. The particle motion in the reactor is computed using the drag laws which depend on the local volume fraction of each phase. Heat transfer from the fluidized bed to the biomass particles together with the pyrolysis reactions were simulated by Fluent CFD code through user-defined function (UDF). Spontaneous production of pyrolysis oil, char and non-condensable gases (NCG) confirm the observation widely reported in literature. The computer model can potentially be used to assess other candidate biomass sources also to assist design of optimized pyrolysis reactors.

Abstract: This study discussed the possibility of employing the Yellow River Silt (YRS) as the starting materials to produce lightweight ceramisite (LWC) by a non-sintering process. Cement and sodium silicate were used as additives. The performance of the LWC serving as a biomedium in a biological aerated reactor (BAF) for hospital wastewater treatment was investigated and the optimum operation condition was studied. Results presented that: (1) YRS could be used to prepare the LWC under the propitious condition (the ratio of YRS to cement was 75:25, the percentage of sodium silicate was 7% and the curing time was 5 d); (2) LWC could be used as a packing medium in the BAF. The BAF has large removal efficiencies on COD¬cr and NH3-N when the hydraulic retention time (HRT), the ratio of air to liquid (A/L) and the height of packing medium were 6 h, 5:1 and 80 cm respectively.