اثر عملیات حرارتی بر ریزساختار و خواص مکانیکی آلیاژ فراریزدانه شبه تیتانیوم β

Effect of Heat Treatment on Microstructure and Mechanical

Properties of Ultra-fine Grained Ti-55511 Near β Titanium Alloy

اثر عملیات حرارتی بر ریزساختار و خواص مکانیکی آلیاژ فراریزدانه شبه تیتانیوم β 

ABSTRACT

The ultra-fine grained (UFG) Ti-55511 near β titanium alloy with grain size 0.1∼0.5 μm was prepared by hot rolling. The effects of heat treatment on the microstructure and mechanical properties were investigated using SEM and TEM. The results indicate that both strength and hardness increase firstly and then reduce with increasing of heat treatment temperature from 350°C to 650°C. The peak strength (1486 MPa) appears at 450°C. The strength dramatically reaches to 1536 MPa and then is stablized with increasing of the holding time when heat treated at 450°C. While the elongation increases firstly and then decreases. The microstructure analysis shows that the dynamic recovery occurs and the grain sizes remain at smaller than 1 μm during annealing. The recovery stimulates the grain refinement effect by eliminating the hardening process and stimulating the grain boundary/phase boundary to be stable. The phase transformation of α→α2 and β→ω→α enhances the second phase particle dispersion effect during annealing. However, the ductility of the alloy could significant decrease when the second phase particles grow up to a certain size. The mechanical properties evolution during annealing are mainly related to the effect of strengthening mechanisms.

 

اثرات ترمودینامیکی بر سینتیک فرآیندهای تولیدکننده‌ی تهی‌جایی

Thermodynamic effects on the kinetics of

vacancy-generating processes

اثرات ترمودینامیکی بر سینتیک فرآیندهای تولیدکننده‌ی تهی‌جایی

ABSTRACT

he inhibiting effect of vacancies on the very process in which they are generated is considered from a thermodynamic viewpoint. Examples of such processes treated here in some detail are grain growth and pore dissolution. It is shown that these processes are inhibited due to vacancy generation. A particular scenario discussed implies intermittent “locking”. After a period of uninhibited kinetics the process comes to a halt due to a thermodynamic back force “locking” it. It can only re-start once the vacancies produced are removed by diffusion. This repetitive cycle leads to an overall reduction in the rate of the kinetic process in question. Specific predictions with regard to grain growth in fine-grained (particularly nanocrystalline) materials and void dissolution kinetics in sintering are made. A third example considered is vacancy drag on a moving individual grain boundary. The magnitude of the drag is re-assessed by taking into account the Gibbs free energy of the vacancies generated.

 

رشد نانولوله‌های کربنی روی فیبرهای کربنی توسط CVD حرارتی

Growth of Carbon Nanotubes on Carbon Fiber by

Thermal CVD Using Ni Nanoparticles as Catalysts

رشد نانولوله‌های کربنی روی فیبرهای کربنی توسط CVD حرارتی

با استفاده از نانوذرات نیکل به عنوان کاتالیزور

ABSTRACT

Nickel nanoparticles and thin film on carbon fiber have been prepared through electroless deposition. Moreover, carbon nanotubes were grown on carbon fiber covered by nickel nanoparticles using thermal chemical vapor deposition. The effects of changes in the thickness of the nickel catalyst layer and the growth temperature of carbon nanotubes were studied systemically, and the results are discussed in the present work.

 

چقرمگی شکست اپوکسی اصلاح شده با لاستیک هیبریدی

Fracture Toughness of a Hybrid-Rubber-Modified

Epoxy. I. Synergistic Toughening

چقرمگی شکست اپوکسی اصلاح شده با لاستیک هیبریدی

 I . اثر تشدید کننده چقرمه شدن

ABSTRACT

The fracture behavior of a hybrid-rubber-modified epoxy system was investigated. The modified epoxy included amine-terminated butadiene acrylonitrile (ATBN) rubber and recycled tire particles as fine and coarse modifiers, respectively. The results of the fracture toughness (KIC) measurement of the blends revealed synergistic toughening in the hybrid system when 7.5-phr small particles (ATBN) and 2.5-phr large particles (recycled tire) were incorporated. Transmission optical micrographs showed different toughening mechanisms for the blends; fine ATBN particles increased the toughness by increasing the size of the damage zone and respective plastic deformation in the vicinity of the crack tip. However, in the case of hybrid resin, coarse recycled rubber particles acted as large stress concentrators and resulted in the branching of the original crack tip. Mode mixity at the branch tips led to synergistic KIC in the hybrid system. It seemed that the ductility of the matrix played an effective role in the nature of the crack-tip damage zone in the hybrid epoxies

 

تاثیر عناصر آلیاژی بر ریزساختار و خواص شکست غلتک‌های فولادی تندبر

Effects of alloying elements on microstructure and fracture properties of cast high speed steel rolls

Part I: Microstructural analysis

تاثیر عناصر آلیاژی بر ریزساختار و خواص شکست غلتک‌های فولادی تندبر

بخش اول: آنالیز ریزساختاری

ABSTRACT

A study was made of the effects of alloying elements on microstructural factors of six high speed steel (HSS) rolls manufactured by centrifugal casting method. Particular emphasis was placed on the role of hard carbides located along solidification cell boundary and the type of the martensite matrix. Microstructural observation, X-ray diffraction analysis, and hardness measurement were conducted on the rolls to identify carbides. Various types of carbides were formed depending on the contents of strong carbide forming elements. In the rolls containing the high Cr content, MC carbides inside cells and M7C3 carbides along cell boundaries were primarily formed, while in the rolls containing the high W and Mo contents, MC carbides inside the cells and fibrous M2C carbides in the intercellular regions were dominantly formed. The most important microstructural factor affecting overall roll hardness was the intercellular carbides and their distribution. The effects of alloying elements were analyzed on the basis of the liquidus surface diagram, suggesting that the proper contents of carbon, tungsten, molybdenum, chromium, and vanadium were 1.9–2.0, 3–4, 3–4, 5–7, and 5–6%, respectively.

 

سنتز و خواص اپتیکی فیلم‌های متخلخل نانوخوشه‌ای ZnO

Synthesis and optical properties of ZnO nanocluster porous

films deposited by modified SILAR method

سنتز و خواص اپتیکی فیلم‌های متخلخل نانوخوشه‌ای ZnO نشانده شده

توسط روش SILAR اصلاح شده

ABSTRACT

possessing wide band gap and large exciton binding energy. The recent discovery of ultraviolet-luminescence at room temperature for ZnO nanomaterial has stimulated great researching interest for its potential applications in various photoelectric devices [1]. ZnO nanocluster film belongs to a new class of ZnO-based photoelectric material. The quantum confinement and the surface state or other in-gap states in ZnO nanocluster could exert strong influence on its electronic state and optical properties [2], thus making it more promising for the production of optical devices. Therefore, the investigation on the optical properties of ZnO nanocluster films is of both fundamental interest and technological importance.

 

سنتز نانو ورقه های ZnO از طریق روش الکترورسوبی

Synthesis of ZnO nanosheets via electrodeposition method and

their optical properties, growth mechanism

سنتز نانو ورقه های ZnO از طریق روش الکترورسوبی ، خواص نوری و مکانیزم رشد

ABSTRACT

ZnO nanosheets were prepared by electrochemical deposition method at 80 C on seeded Indium Tin Oxide conducting glass substrates. The seed layer was coated on ITO by spin coating and annealed at 350 C for 30 min prior to electrochemical deposition growth. X-ray diffraction patterns (XRD) and field emission scanning electron microscope (FESEM) images confirmed that the ZnO nanosheets consist of polycrystalline structures. Room temperature photoluminescence spectra (PL) of the ZnO nanosheets exhibited band-edge ultraviolet (UV) and visible emission (blue) indicating the ZnO nanosheets had excellent optical properties. The UV–Vis absorption spectrum of ZnO nanosheets was shown a strong absorption at 300 nm. The ZnO nanosheets structure demonstrated higher photocatalytic activity during degradation of aqueous methylene blue under visible-light irradiation. Moreover, the growth mechanism of the ZnO nanosheets had been discussed.

 

آنالیز SEM و اشعه ایکس - SEM and X-ray Microanalysis

SEM and X-ray Microanalysis Image Formation and Interpretation

آنالیز اشعه ایکس و SEM - تفسیر و تشکیل تصویر

ABSTRACT

Scanning electron microscopy is a technique in which images form the major avenue of information to the user. A great measure of the enormous popularity of the SEM arises from the ease with which useful images can be obtained. Modern instruments incorporate many computer-controlled, automatic features that permit even a new user to rapidly obtain images that contain fine detail and features that are readily visible, even at scanning rates up to that of television (TV) display. Although such automatic “computer-aided” microscopy provides a powerful tool capable of solving many problems, there will always remain a class of problems for which the general optimized solution may not be sufficient.

اثر ایتربیم روی خواص مکانیکی و ریزساختار آلیاژ آلومینیوم-منیزیم

Effects of Yb on the mechanical properties and microstructures of an Al–Mg alloy

اثر ایتربیم روی خواص مکانیکی و ریزساختار آلیاژ آلومینیوم-منیزیم

ABSTRACT

This paper reported a first study of the effects of Yb on the microstructures and mechanical properties of an extruded Al–Mg alloy. It has been shown that the addition of 0.3 wt.% Yb decreases the mechanical properties of the alloy since Mg- and Yb-containing constituents decrease the concentration of Mg solute atoms in Al matrix, and thus the solution strengthening effect. However, the addition of 1 wt.% Yb substantially improves the mechanical behavior of the alloy because the concentration of Yb solute atoms in Al matrix is high enough to generate solution strengthening effect. The improvement in the mechanical properties is due to the large work-hardening and high dislocation density caused by the interaction between dislocations and Yb and Mg solute atoms. The Yb and Mg atoms inhibit the dynamic recovery and recrystallization of the alloy, thus provide a uniformly distributed dislocation structure with high density.

 

ساخت پودرهای فلزی توسط الکترولیز

Forming metal powders by electrolysis

ساخت پودرهای فلزی توسط الکترولیز

ABSTRACT

Fossil fuels will eventually be replaced by renewables. Currently, the most feasible and efficient way of utilising renewable energy is to convert it to electricity. In response to this change, fossil energy-based pyrometallurgical processes will inevitably shift to electricity driven processes. This chapter considers the feasibility of direct conversion of mineral to metal powder using a new electrochemical method, the FFC Cambridge process. The discussion will be on the background of electrometallurgy and powder metallurgy, the principles of the new process and its application for metal powder production, and the direct route from oxide precursors to alloyed powders.