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پلاستیک ها، الاستومر ها و کامپوزیت ها به منظور کنترل خوردگی

 Using Plastics, Elastomers, and Composites for Corrosion Control

استفاده از پلاستیک ها، الاستومر ها و کامپوزیت ها به منظور کنترل خوردگی 

ABSTRACT

This chapter provides a broad overview of the application of polymers used for corrosion control in the chemical proces- sing industry. The generalizations offered about polymer performance might suggest possible approaches, but they should not be considered as recommendations owing to the complexity of equipment design and the many variables of chemical processing. Consultations with experts, analyses of case histories, and testing are essential to the success of these materials.

ادامه نوشته

افزودن تیتانیم روی فولاد کم آلیاژ استحکام بالا Effect of Titanium Addition on HSLA Steel

Study on the Mechanism of Strengthening and Toughening Effect

 of Titanium Addition on HSLA Steel 

مطالعه‌ی مکانیزم استحکام‌بخشی و اثر چقرمه‌سازی افزودن تیتانیم روی فولاد HSLA

ABSTRACT

Based on the determination of load variation against deflection by means of Instrumented Charpy Impact testing, the impact energy distribution of the High Strength Low Alloy (HSLA) steel containing Nb, Ni and Ti for pressure vessels at low temperature has been quantitatively studied. The total impact energy Et could be divided into two parts, Ei  and Ep. Ei is related to the base strength of the material in terms of the grain size and alloy addition, which is also found to be less influenced by the holding time of normalization process at 910℃. Whereas, Ep of Ni-Nb-Ti HSLA steel is strongly linked to the period of holding time. Thermodynamic kinetic investigation was  carried out to study the strengthening mechanism with metallurgical microstructure analysis. 

 

ادامه نوشته

مواد کنتاکت از جنس آلیاژ قلع-نقره AgSnO2 Electrical Contact Materials

Research on the Organization Performance of

AgSnO2 Electrical Contact Materials

پژوهشی درباره‌ی رفتار تشکیل در مواد کنتاکت از جنس AgSnO2 

ABSTRACT

In electrical contact materials, silver metal oxide (AgMeO) materials because has good resistance to  abrasion, fusion welding resistance and electrical conductivity, is widely used in low-voltage  electrical appliances. And  silver cadmium oxide (AgCdO) because it has excellent electric arc  erosion resistance, fusion welding resistance so was widely used in from a few volts to kv in a  variety of low-voltage electrical appliances. The material because of a series of excellent  performance has been called the universal contact.

ادامه نوشته

بهبود یک فولاد میکروآلیاژی HSLA با وانادیم و تیتانیم

Effect of vanadium and titanium modification on the microstructure and

mechanical properties of a microalloyed HSLA steel

اثر بهبود یک‌نوع فولاد میکروآلیاژی HSLA با وانادیم و تیتانیم بر ریزساختار و خواص مکانیکی آن

ABSTRACT

Microalloyed high-strength low-alloy (HSLA) steels are essentially low carbon low-alloy steels that contain small additions (0.001–0.1wt.%) of alloying elements such as Nb, V, or Ti. These steels exhibit an outstanding combination of high strength, resistance to brittle fracture and good weldability, particularly if the carbon content is kept below ∼0.1wt.% . Several categories of HSLA steels have been developed catering to the needs of specific applications, such as the construction of large ships, oil and gas transmission lines, and offshore oil drilling platforms.

ادامه نوشته

آنالیز میکروسکوپ تونلی روبشی STM و میکروسکوپ نیروی روبشی SFM

scanning tunneling microscope (STM) 

Scanning Force Microscopy (SFM) 

آنالیز میکروسکوپ تونلی روبشی STM و میکروسکوپ نیروی روبشی  SFM

ABSTRACT

Scanning tunneling microscopy (STM) and its offspring, scanning force microscopy (SFM) , are real-space imaging techniques that can produce topographic images of a surface with atomic resolution in all three dimensions. Almost any solid surface can be studied with STM or SFM : insulators, semiconductors, and conductors, transparent as well as opaque materials. Surfaces can be studied in air, in liquid, or in ultrahigh vacuum, with fields of view from atoms to greater than 250*250um. With this flexibility in both the operating environment and types of samples that can be studied, STM/SFM is a powerful imaging system.

 

ادامه نوشته

سلول های خورشیدی از تک کریستال های Si تا مواد متخلخل

A review on solar cells from Si-single crystals

to porous materials and quantum dots

مروری بر سلول های خورشیدی از تک کریستال های Si تا نقاط کوانتومی و مواد متخلخل

ABSTRACT

Solar energy conversion to electricity through photovoltaics or to useful fuel through photoelectrochemical cells was still a main task for research groups and developments sectors. In this article we are reviewing the development of the different generations of solar cells. The fabrication of solar cells has passed through a large number of improvement steps considering the technological and economic aspects. The first generation solar cells were based on Si wafers, mainly single crystals. Permanent researches on cost reduction and improved solar cell efficiency have led to the marketing of solar modules having 12–16% solar conversion efficiency. Application of polycrystalline Si and other forms of Si have reduced the cost but on the expense of the solar conversion efficiency. The second generation solar cells were based on thin film technology. Thin films of amorphous Si, CIS (copper–indium–selenide) and t-Si were employed. Solar conversion efficiencies of about 12% have been achieved with a remarkable cost reduction. 

ادامه نوشته

زینترینگ سرامیک های Nd:YAG شفاف تحت اتمسفر اکسیژن

Sintering of transparent Nd:YAG ceramics in oxygen atmosphere 

زینترینگ سرامیک های Nd:YAG شفاف تحت اتمسفر اکسیژن

ABSTRACT

Yttrium aluminum garnet (YAG) transparent ceramics were fabricated by sintering at oxygen atmosphere. Tetraethyl orthosilicate (TEOS) was added as the sintering additive to control the grain growth and densification. Pores were eliminated clearly at temperature lower than 1700 °C, while grain size was around 3 μm. The in-line transmittance was 80% at 1064 nm when samples were sintered at 1710 °C. The effect of TEOS was studied in oxygen atmosphere sintering for Nd:YAG transparent ceramics. At higher temperature like 1710 °C, the grain growth mechanism was solute drag, while at 1630 and 1550 °C the grain growth was controlled by liquid phase sintering mechanism. And 0.5 wt.% TEOS was the best adding content for Nd:YAG sintered in oxygen atmosphere.

 

ادامه نوشته

تک کریستال Si تشکیل شده روی لایه آمورف در دمای پایین

Single-crystal Si formed on amorphous substrate at

low temperature by nanopatterning and

nickel-induced lateral crystallization

تک کریستال Si تشکیل شده روی لایه آمورف در دمای پایین

ABSTRACT

Silicon-based thin film transistors ~TFTs! on an amor- phous substrate have many important applications, including active matrix liquid-crystal display ~AMLCD! and future 3-dimensional ~3D! integrated circuits. However, silicon films deposited on amorphous substrate are typically in amorphous, microcrystalline, or polycrystalline states, which contain tremendous intrinsic defects, resulting in poor device performance and device-to-device nonuniformity. A single- crystal silicon film on amorphous substrate is highly desired but is difficult to achieve because single-crystal silicon can- not grow epitaxially on an amorphous substrate. Low tem- perature is also desired to lower the manufacturing cost and ensure the circuit integration.

ادامه نوشته

بازرسی جریان گردابی پالسی Pulsed Eddy Current Inspection

Pulsed Eddy Current Inspection of Support Structures

in Steam Generators

بازرسی جریان گردابی پالسی برای سازه های نگهدارنده در ژنراتورهای بخار 

ABSTRACT

Degradation and fouling of support structures in nuclear steam generators (SGs) can lead to SG tube damage and loss of SG efficiency. Inspection and monitoring of support structures combined with preventative maintenance programs can alleviate these effects and extend SG life. Conventional eddy current inspection technologies are extensively used for detecting and sizing indications from wall loss, frets at supports, cracks and other degradation modes in the tubes, as well as assessing the condition of support structures. However, these methods have limited capabilities when more than one degradation mode is present simultaneously, or when combined with fouling. Pulsed eddy current combined with principal components analysis (PCA) was examined for inspection of 15.9 mm (5/8") Alloy-800 tubes and surrounding stainless steel (SS410) support structures. Clear separation of PCA scores associated with tubes from those associated with ferromagnetic SS410 supports permitted measurement of tube-to-support gaps, in either the presence of tube fretting or variation of relative position of the tube within SS410 supports. For concentric tubes, frets could be sized independently of SS410 hole diameter variations, which in other materials could represent support corrosion. Capability to clearly separate scores was attributed to large differences in relaxation times for diffusion of transient fields through the tube compared with diffusion into the ferromagnetic support structure.

ادامه نوشته

تاثیر پوشش های محافظ بر خواص مکانیکی سوپر آلیاژها Superalloys

The Effect of Protective Coatings on

the Mechanical Properties of Superalloys

تاثیر پوشش های محافظ بر خواص مکانیکی سوپر آلیاژها

ABSTRACT

COATINGS PROTECT the surface of tur- bine blades from damage caused by high-tem- perature corrosion and thus preserve the struc- tural shape of blades and their mechanical properties for the required time. There are many papers in the technical liter- ature that deal with experimental studies of heat resistance, fatigue strength, and thermal fatigue of coated superalloys. However, the connection between the physical and mechanical properties of protective coatings and their effect on the me- chanical properties of turbine-blade superalloys has not been studied sufficiently well. For thin diffusion coatings, this can be explained by the complexity of the task, both in reproducing the correct composition and in testing the coatings separately from the alloy. However, for these coatings, information on their physical and me- chanical properties is necessary for their proper application and for accurate calculations of coated-blades service lives.

ادامه نوشته

پیشرفت هایی در NDT و مشخصه یابی مواد توسط جریان گردابی

Advances in NDT and materials characterization by eddy currents 

پیشرفت هایی در NDT و مشخصه یابی مواد توسط جریان گردابی

ABSTRACT

Non-Destructive Testing (NDT) plays a vital role to achieve reliability and quality at an acceptable cost. Failures of engineering materials, components and structures are well known and can be disastrous [1]. Avoiding the failures cost effectively ensuring safety of use and reliability on a wide range of industrial components are the major industrial NDT objectives. NDT is facing new challenges for defect detection and quality control of advanced engineering materials such as in multi-material structures [2], non-ferrous alloys for advanced lightweight structures, composites [3] (GLARE), carbon resins composite, Fiber-reinforced Metal Laminates (FML), High Performance Thermoplastic Composites (HPTC) and Metal Matrix Composites (MMC)). In the scope of recent production technologies: Friction Stir Welding (FSW), Friction Surfacing, Friction Stir Processing (FSP) and Single Point Incremental Forming (SPIF), innovative NDT techniques and technologies are required, and must be transfered from research to industry as quickly as possible to solve these challenges.

ادامه نوشته

فولادهای میکروآلیاژی وانادیوم-نیوبیوم vanadium-niobium microalloyed steels

As-cast mechanical properties of vanadium/niobium microalloyed steels

خواص مکانیکی فولادهای میکروآلیاژی وانادیوم/نیوبیوم

ABSTRACT

Tensile and room temperature Charpy V-notch impact tests along with microstructural studies were used to evaluate the variations in the as-cast mechanical properties of low-carbon steels with and without vanadium and niobium. Tensile test results indicate that good combinations of strength and ductility can be achieved by microalloying additions. While the yield strength and UTS increase up to respectively 370–380 and 540–580 MPa in the microalloyed heats, their total elongation range from 20 to 25%. TEM studies revealed that random and interphase fine-scale microalloy precipitates play a major role in the strengthening of the microalloyed heats. On the other hand, microalloying additions significantly decreased the impact energy and led to the dominance of cleavage facets on the fracture surfaces. It seems that heterogeneous nucleation of microalloy carbonitrides on dislocations along with coarse ferrite grains and pearlite colonies trigger the brittle fracture in the microalloyed heats.

ادامه نوشته

فولادهای زنگ نزن آستنیتی نیکل پایین Low Nickel Austenitic Stainless Steels

Low Nickel Austenitic Stainless Steels 

فولادهای  زنگ نزن آستنیتی نیکل پایین

ABSTRACT

The most common grades of stainless steel are 304 and 316, which are particularly popular because  their austenitic microstructure results in an excellent combination of corrosion resistance, mechanical  and physical properties and ease of fabrication.  The austenitic structure is the result of the addition of approximately 8-10% nickel. Nickel is not alone  in being an austenite former; other elements that are used in this way are manganese, nitrogen,  carbon and copper. 

ادامه نوشته

ارزیابی عمق ترک با استفاده از تکنیک های جریان گردابی

Evaluation of crack depth using eddy current techniques

with GMR-based probes

ارزیابی عمق ترک با استفاده از تکنیک های جریان گردابی با پروب ها بر پایه - GMR

ABSTRACT

This paper presents experimental and simulated results obtained using the eddy current nondestructive method to conclude about the depth of linear cracks machined on an aluminum plate. Experimental tests were performed with a sinusoidal excitation field of fixed-amplitude and with a giant magnetoresistance-based sensor to measure the resultant magnetic field on the plate surface. To validate and better insight the experimental results, numerical simulations have been carried out with a commercial program for conditions similar to the experimental case studies. A scheme to infer about crack depth is proposed.

ادامه نوشته

خواص مکانیکی جوشکاری اصطکاکی اغتشاشی آلیاژ آلومینیوم در زیر آب

Homogeneity of Mechanical Properties of Underwater

Friction Stir Welded 2219-T6 Aluminum Alloy

یکنواختی خواص مکانیکی جوشکاری آلیاژ آلومینیوم 2219-T6

جوشکاری اصطکاکی اغتشاشی شده درزیر آب

ABSTRACT

Underwater friction stir welding (FSW) has been demonstrated to be available for the improvement in tensile strength of normal FSW joints. In order to illuminate the intrinsic reason for strength improvement through underwater FSW, a 2219 aluminum alloy was underwater friction stir welded and the homogeneity of mechanical properties of the joint was investigated by dividing the joint into three layers. The results indicate that the tensile strength of the three layers of the joint is all improved by underwater FSW, furthermore, the middle and lower layers have larger extent of strength improvement than the upper layer, leading to an increase in the homogeneity of mechanical properties of the joint. The minimum hardness value of each layer, especially the middle and lower layers, is improved under the integral water cooling effect, which is the intrinsic reason for the strength improvement of underwater joint.

 

ادامه نوشته

اثر سرعت جوشکاری اصطکاکی اغتشاشی در زیر آب روی آلیاژ آلومینیوم

Effect of welding speed on microstructures and mechanical properties

of underwater friction stir welded 2219 aluminum alloy

اثر سرعت جوشکاری بر ریز ساختارها و خواص مکانیکی آلیاژ آلومینیوم 2219

جوشکاری اصطکاکی اغتشاشی شده در زیر آب 

ABSTRACT

Underwater friction stir welding (underwater FSW) has been demonstrated to be available for the strength improvement of normal FSW joints. In the present study, a 2219 aluminum alloy was underwater friction stir welded at a fixed rotation speed of 800 rpm and various welding speeds ranging from 50 to 200 mm/min in order to clarify the effect of welding speed on the performance of underwater friction stir welded joint. The results revealed that the precipitate deterioration in the thermal mechanically affected zone and the heat affected zone is weakened with the increase of welding speed, leading to a narrowing of softening region and an increase in lowest hardness value. Tensile strength firstly increases with the welding speed but dramatically decreases at the welding speed of 200 mm/min owing to the occurrence of groove defect. During tensile test, the joint welded at a lower welding speed is fractured in the heat affected zone on the retreating side. While at higher welding speed, the defect-free joint is fractured in the thermal mechanically affected zone on the advancing side.

ادامه نوشته

تجهیزات در آزمون جریان گردابی Eddy current testing

Eddy current sensors

سنسورهای جریان گردابی

ABSTRACT

In addition to tavtile ( gauging ) sensors, non contantct metrology is now also used to measure displacement, deformation,, stretching, distances, position and other geometrical shapes and sozes. These sensors often measure faster, more accurately and more reliably than tactile sensors. The measurement data is normally available in real time to automatically regukate and control the production. Quality control is not only carried out on finished products, but metrology can also supervise and optimize production processes. The aim is to improve product quality, reduce rejects to a minimum and to lower total production costs. 

ادامه نوشته

حفاظت کاتدی - آزمون دیاگنوستیک Cathodic Protection Procedures

Cathodic Protection  Procedures - Diagnostic Testing

حفاظت کاتدی - آزمون دیاگنوستیک (ملزومات جریان)

ABSTRACT

The purpose of  diagnostic testing (DT)  is to outline a process to test for deficiencies  in a cathodic protection (CP) system, to identify  the cause(s)  of  such deficiencies, and to determine the requirements  to enhance the level of CP  to the structure. In an existing CP system, the DT is to first determine  if  the cause of  low CP levels can be eliminated and, if  not, what additional current is required, in addition  to how and where it can be applied. The CP Technician must have a good understanding of  the criteria as well as  the special conditions and precautionary notes that apply  to  these  criteria.

ادامه نوشته

اثرات آنتی باکتریال فلزات Antibacterial effects of metals

Antibacterial effects of metals 

اثرات آنتی باکتریال فلزات

ABSTRACT

In this chapter, the antibacterial effects of metals will be described first, and it will be compared with photocatalytic oxides and organics. Then , anti bacterial coating that have been proposed in practical industries will be introduced. The merits and demerits will be discussed, and the concept of composite materials for antibacterial effect will be proposed followed by a detail discussion. Some possibilities will be mentioned. And finally, the two concrete examples by the authors will be introduced and explained.

ادامه نوشته

جوشکاری اصطکاکی نقطه‌ای آلیاژ آلومنیوم-لیتیم aluminium–lithium 2A97 alloy

Microstructure and mechanical properties of

friction spot welding aluminium–lithium 2A97 alloy

ریزساختار و ویژگی‌های مکانیکی جوشکاری اصطکاکی نقطه‌ای آلیاژ آلومنیوم-لیتیم 2A97

ABSTRACT

In this study, we investigated the microstructure and mechanical properties in different regions of the friction spot welded 2A97 aluminium-lithium alloy subjected to different heat treatment processes. The 2.0. mm thick hot-rolled sheet of 2A97 alloy was successfully welded using friction spot welding method with optimised welding parameters. Afterwards, the as-welded 2A97 joints experienced two subsequent heat treatment procedures: solution and ageing; directly ageing. The corresponding microstructure and mechanical properties of the heat-treated specimens were studied by means of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), hardness test and tensile test. The results show that the mechanical properties of the 2A97 joints before and after heat treatment were significantly modified, which was mainly related to fine-grained microstructure, size and type of precipitates, and dislocation density. Compared to the base material and the material that only experienced direct ageing, the whole friction spot welded 2A97 joint after solution and ageing treatment delivered better mechanical properties.

ادامه نوشته

بیومواد آلومینا چقرمه شده با زیرکونیا برای جایگزین مفصل

Advances in zirconia toughened alumina biomaterials

for total joint replacement

پیشرفت ها در بیومواد آلومینا چقرمه شده با زیرکونیا برای جایگزین کلی مفصل

ABSTRACT

The objective of this article is to provide an up-to-date overview of zirconia-toughened alumina (ZTA) components used in total hip arthroplasties. The structure, mechanical properties, and available data regarding the clinical performance of ZTA are summarized. The advancements that have been made in understanding the in vivo performance of ZTA are investigated. This article concludes with a discussion of gaps in the literature related to ceramic biomaterials and avenues for future research.

ادامه نوشته

مواد ایمپلنت سرامیکی Ceramic Implant Materials

Ceramic Implant Materials

مواد ایمپلنت سرامیکی

ABSTRACT

Ceramics are refractory, polycrystalline compounds, usually inorganic, including silicates, metallic oxides, carbides, and various refractory hydrides, sulfides, and selenides. Oxides such as Al2O3, MgO, SiO2, etc. contain metallic and nonmetallic elements. Ionic salts (NaCl, CsCl, ZnS, etc.) can form polycrystalline aggregates, but soluble salts are not suitable for structural biomaterials. Diamond and carbonaceous structures like graphite and pyrolized carbons are  covalently bonded. The important factors influencing the structure and property relationship of  the ceramic materials are radius ratios (§2.2.2) and the relative electronegativity between posi- tive and negative ions. 

ادامه نوشته

نیتروژن دهی یون-پلاسمایی فولاد ابزار ماشین آلات و قطعات

Ion-plasma nitriding of machines and tools parts instrumental steels

نیتروژن دهی یون - پلاسمایی فولاد ابزار ماشین آلات و قطعات 

ABSTRACT

Here introduced features of formation diffusion bond during ion nitriding in glow discharge plasma in gaseous mediums (mixture of nitrogen and argon). It is shown, that argon existing in saturated medium changes the nitriding process kinetics and the phase composition of the outer zone. Here presented investigation results on ion-plasma nitriding of instrumental steels, focused on microstructure and tool areas phase composition change, operating in most difficult conditions.

ادامه نوشته

نیتروژن دهی پلاسمایی و عملیات رسوب سختی فولاد مارجینگ

Effect of Simultaneous Plasma Nitriding and Aging Treatment

on the Microstructure and Hardness of Maraging 300 Steel

تاثیر همزمان نیتروژن دهی پلاسمایی و عملیات رسوب سختی بر میکروساختار و سختی فولاد مارجینگ 300

ABSTRACT

Simultaneous nitriding and aging heat treatment of maraging 300 steel was carried out inside a DC-pulsed plasma nitriding reactor. A single heat treatment cycle was done, as the plasma nitriding and age hardening processes occur at the same ranges of temperatures and times. Samples of maraging 300 steel, in the solution annealed and solution annealed and aged conditions, were tested. Plasma nitriding and aging, carried out at 480 °C for 3 h, increased the surface hardness up to 1140 HV, producing case depths of 50 μm since ε-Fe3N and γ′-Fe4N nitrides were formed in the hardened surface layer. It is observed that the microstructure of the core material remains unaltered as the typical martensite plate-like microstructure of maraging steels. The core hardness of solution annealed samples increased from 331 to 597 HV after the plasma nitriding treatment proving the possibility of nitriding and aging at the same treatment cycle. The pre-aged samples did not show any overaging or martensite reversion to austenite after the simultaneous plasma nitriding and aging treatments, that could be showed by the core hardness of 620 HV and can be related to the time of total aging exposure of 6 h, including pre-aging and plasma nitriding.

ادامه نوشته

خستگی خوردگی در آلیاژ آلومینیوم – منیزیم بسیار ریزدانه

A microscopic study on the corrosion fatigue of ultra-fine grained

and conventional Al–Mg alloy

مطالعه میکروسکوپی خستگی خوردگی در آلیاژ آلومینیوم – منیزیم بسیار ریزدانه و مرسوم

ABSTRACT

The corrosion behavior of a nanocrystalline (NC)/ultrafine grained (UFG) Al–Mg based alloy was investigated and compared to its conventional counterpart 5083(H111). The corrosion fatigue (CF) was studied with respect to pit initiation, pit location and crack propagation as a function of environment. Scanning electron microscopy (SEM) with EDS was used to analyze the fracture surface of the failed specimen with respect to pitting characteristics, crack propagation and corrosion product. Load vs. cycles to failure was measured and S/N curves were generated for the UFG Al–Mg based alloy and the conventional counterpart 5083 in air and seawater.

ادامه نوشته

نیتروژن دهی و آلیاژسازی سطح فولادها با اتم های Ti و Nb توسط عملیات تراکمی جریان های پلاسمایی

Surface nitriding and alloying of steels with Ti and Nb atoms

by compression plasma flows treatment

نیتروژن دهی و آلیاژسازی سطح فولادها با اتم های Ti و Nb توسط عملیات تراکمی جریان های پلاسمایی

ABSTRACT

Phase and element composition, microhardness of Ti/steel and Nb/steel systems treated by compression plasma flows have been investigated in this work. Auger electron spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersion X-ray microanalysis and Vickers microhardness measurements were used for sample characterization. The findings showed that treatment of a “coating/steel” system by compression plasma flows generated in nitrogen atmosphere allowed alloying of the surface layer of steel by the coating element and nitriding it simultaneously. The variation of the pulses number (1–6) resulted in change of the alloying element concentration and formation of a number of phases in the alloyed layer: Fe2Ti, a supersaturated solid solution α-Fe(Ti,C) in the Ti alloyed layer and a supersaturated solid solution α-Fe(Nb,C) in the Nb alloyed layer. The formation of Ti(C,N) and Nb(C,N) carbonitrides with fcc crystal structure at the surface was also found. The change of phase composition and quenching effects resulted in substantial increase of microhardness.

ادامه نوشته

نیتروژن دهی پلاسمایی فولاد زنگ نزن نوع AISI 420

Effect of plasma nitriding on the strength of

fine protrusions formed by sputter etching of

AISI type 420 stainless steel

تاثیر نیتروژن دهی پلاسمایی بر استحکام برآمدگی های ریز تشکیل شده

از اچ کند و پاشی (sputter etching)  فولاد زنگ نزن نوع AISI 420

ABSTRACT

Argon ion sputter-etching of AISI type 420 martensitic stainless steel was carried out to form conical protrusions with bottom diameter of 10–30 μm on the specimen surface by using a radio-frequency magnetron sputter-apparatus. Plasma-nitriding was applied to the protrusions with various mixing rate of nitrogen and argon gas. The shape of the protrusions was examined by using a scanning electron microscope, and the nitrides formed on the protrusions were identified by means of an X-ray diffraction analysis. Micro-Vickers hardness tests and nano-scratch tests were used to evaluate the deformation resistance of the protrusions. By plasma-nitriding at a nitrogen pressure of 130 Pa and a nitriding power of 50 W, about 1.3 times larger indentation resistance than that of the as-sputter-etched protrusions was obtained after a long nitriding time of 14 ks. When plasma-nitriding was carried out at a lower nitrogen pressure of 1.2 Pa and a higher nitriding power of 200 W for 7.2 ks, indentation and scratch resistances of the protrusions largely increased to the values almost three times as large as those of the as-sputter-etched protrusions. However, the protrusions were brittle due to the formation of thick nitride layers and the sharpness of the protrusions was lost. Reduction of the nitriding power to 50 W recovered the sharpness with small amount of surface nitride layer, but the indentation resistances were only 1.4 times larger values than those of the as-sputter-etched protrusions. On the other hand, plasma-nitriding using a mixture of nitrogen gas of 0.53 Pa and argon gas of 0.67 Pa at the power of 50 W produced almost twice larger indentation and scratch resistances than those of the as-sputter-etched protrusions within a short nitriding time of 1.8 ks, retaining the sharpness of protrusions without forming brittle nitrided layers.

ادامه نوشته

حساسیت به ترک انجمادی در فلزهای جوش آلیاژهای آلومینیوم

Solidification crack susceptibility of aluminum alloy weld metals 

حساسیت به ترک انجمادی در فلزهای جوش آلیاژهای آلومینیوم

ABSTRACT

The susceptibilities of the three aluminum alloys to solidification crack were studied with trans-varestraint tests and tensile tests at elevated temperature. Their metallurgical characteristics, morphologies of the fractured surface and dynamic cracking behaviors at elevated temperature were analyzed with a series of micro-analysis methods. The results show that dynamic cracking models can be classified into three types. The first model has the healing effect which is called type A. The second is the one with deformation and breaking down of metal bridge, called type B. The last one is with the separation of liquid film along grain boundary, called type C. Moreover, the strain rate has different effects on crack susceptibility of aluminum alloys with different cracking models. ZL101 and 5083 alloys belong to type A and type C cracking model respectively, in which strain rate has greater effect on eutectic healing and plastic deformation of metal bridge. 6082 alloy is type B cracking model in which the strain rate has little effect on the deformation ability of the liquid film.

 

ادامه نوشته

احیای گندله‌های کوره‌ی بلند اولیوینی

Mineral Reactions and Slag Formation During Reduction

of Olivine Blast Furnace Pellets

واکنش‌های کانی‌ها و تشکیل سرباره در طی احیای گندله‌های کوره‌ی بلند اولیوینی

ABSTRACT

The present work focuses on mineral reactions and slag formation of LKAB olivine iron ore pellets (MPBO) subjected to reducing conditions in the LKAB experimental blast furnace (EBF). The emphasis is on olivine reactions with surrounding iron oxides. Many factors influence the olivine behaviour. The study was performed by use of micro methods; optical microscopy, micro probe analysis, micro Raman and Mössbuer spectroscopy and thremodynamic modeling. During manufacturing, in oxidising atmosphere at high temperature (1350°C), olivine alterations occur through slag formation and rim reactions with iron oxides and other additives. To be able to describe olivine behaviour in the rather complex blast furnace reduction process one has to consider factors such as reactions kinetics, reduction degree of iron oxides, vertical and horizontal position in the furnace and reactions with alkali. Samples were collected from the EBF both from in shaft probing during operation and from excavation following quenching of the EBF.

ادامه نوشته