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.

 

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.

 

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.

 

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.

 

فرآیند شکل دهی ادغام شده با لحیم کاری القایی Induction Brazing

Forming Process Integrated Induction Brazing 

فرآیند شکل دهی ادغام شده با لحیم کاری القایی

ABSTRACT

Processing steps additional to forming operations, such as joining, usually require a vast effort for transport and storage. Due to integration of currently external production steps, processes could be synchronized. Brazing represents an additional operation, which is likely to gain of importance in the light of an increasing relevance of light weight construction. Servo presses enable an adjustment of the ram motion to process requirements. Hence, the ram motion can be adjusted to create a time slot for the execution of additional processes inside the press. In this paper, the possibility to integrate brazing into forming process chains is investigated.  For a demonstration part, a tool that allows brazing inside a servo press is developed. Achievable part qualities and cycle times are  evaluated. 

 

رفتار خستگی خوردگی آلیاژ آلومینیوم جوشکاری شده

Corrosion fatigue behaviour of aluminium alloy 6061-T651 welded

using fully automatic GMAW and ER5183 filler alloy

رفتار خستگی خوردگی آلیاژ آلومینیوم 6061-T651 جوش داده شده با (GMAW)

با آلیاژ ER5183 به عنوان فیلر

ABSTRACT

The fatigue life of aluminium 6061-T651 at various applied stress amplitudes in the unwelded and welded condition was found to be significantly reduced on immersion in a 3.5% NaCl simulated sea water solution, compared to that measured in ambient air. The ratio of fatigue life in NaCl test solution to that in air increased as the stress amplitude decreased. The observed reduction in the fatigue life in the NaCl test solution was most likely due to the presence of pits which nucleated on second phase particles or precipitates. Welded joints performed using pulsed gas metal arc welding and ER5183 filler wire failed at the interface between the weld metal and the heat-affected zone as a result of a high pitting rate in this region.

 

خوردگی ترک تنشی بر روی خطوط انتقال گاز

Stress-Corrosion Cracking On Gas-Transmission Pipelines

history, causes, and mitigation

خوردگی ترک تنشی بر روی خطوط انتقال گاز :

تاریخچه، علل ایجاد و راه های کاهش خطرات

ABSTRACT

This paper reviews the historical data concerning external stress-corrosion  cracking (SCC) of gas transmission pipelines as it has evolved since 1965 and the factors controlling such SCC (eg, pipe environment, steel, and operation). Discussion of these Factors leads to identification of ways in which this cracking can be controlled / mitigated – in the practical setting of an operating pipeline that is expected to provide a reasonable return on equity.

 

ریزساختار و خواص مکانیکی آلیاژ تیتانیوم پس از عملیات حرارتی

Microstructure and mechanical properties of 

TC21 titanium alloy after heat treatment 

ریزساختار و خواص مکانیکی آلیاژ تیتانیوم TC21 پس از عملیات حرارتی

ABSTRACT

Microstructure evolutions during different heat treatments and influence of microstructure on mechanical properties of TC21 titanium alloy were investigated. The results indicate that the excellent mechanical properties can be obtained by adopting air cooling after forging followed by heat treatment of (900 °C, 1 h, AC)+(590 °C, 4 h, AC). Deformation in single β field produces pan-like prior β grains, while annealing in single β field produces equiaxed prior β grains. Cooling rate after forging or annealing in single β field and the subsequent annealing on the top of α+β field determine the content and morphology of coarse α plates. During aging or the third annealing, fine secondary α plates precipitate. Both ultimate strength and yield strength decrease with the content increase of coarse α plates. Decreasing effective slip length and high crack propagation resistance increase the plasticity. The crisscross coarse α plates with large thickness are helpful to enhance the fracture toughness.

 

روند پیشرفت نظریه انجماد غیر تعادلی

Progress of Nonequilibrium Solidification Theory

روند پیشرفت نظریه انجماد غیر تعادلی

ABSTRACT

This paper summarized the theory related to nucleation, interface kinetics, micromorphology evolution and microscopic growth during nonequilibrium alloy solidification. Methods for quantitative analysis of nucleation rate, the criterion of marginal stability, nonequilibrium partition coefficient, as well as the relationship between growth rate with undercooling and dendrite tip radius are presented. Some limitations and future developments of nonequilibrium theory are pointed out.

 

آندایزینگ و عملیات حرارتی تیتانیوم متخلخل

Effects of anodizing parameters and heat treatment on 

nanotopographical features, bioactivity, and cell culture 

response of additively manufactured porous titanium 

اثر پارامترهای آندایزینگ و عملیات حرارتی بر نانو عوارض سطحی، زیست‌فعالی

و پاسخ کشت سلول در تیتانیوم متخلخل ساخته‌شده به روش افزایشی

ABSTRACT

Anodizing could be used for bio-functionalization of  the surfaces of  titanium alloys. In this study, we use anodizing for creating nanotubes on the surface of porous titanium alloy bone substitutes manufactured using selective laser melting. Different sets of anodizing parameters (voltage: 10 or 20 V anodizing time: 30 min to 3 h) are used for anodizing porous titanium  structures that were later heat treated at 500o  C. The nanotopographical features are examined  using electron microscopy while the bioactivity of anodized surfaces is measured using  immersion tests in the simulated body fluid (SBF).