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.

 

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. 

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

بهبود سینترینگ سنگ آهن با الیوین SeqiOlivine improves the sintering of iron ore

SeqiOlivine improves the sintering and

pelletizing performance of iron ore

 الیوین بهبود دهنده عملکرد سینترینگ سنگ آهن 

ABSTRACT

Minelco, the industrial minerals company, started a couple of years back to investigate the possibility of utilizing an olivine-rich dunite rock at Greenland as a source of olivine to different industrial applications. The usage of olivine in industrial applications is predominantly as a slag conditioner and fluxing agent into different metallurgical processes and products, where addition to the blast furnace process, to the sintering of iron ore and iron ore pelletizing are the main areas. In this investigation the usefulness of the olivine mined at Greenland for sinter - and pellet production was studied. The chemical analysis of the olivine from Greenland shows an olivine mineral with high fosterite content. Sintering behaviour and sinter properties shows that the Greenland olivine is a high-rated olivine additive.