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Investigation of Microstructure, Mechanical and Corrosion Properties of Biodegradable Mg-Ag Alloys

Elen Levent, Turen Yunus, Ahlatci Hayrettin, Sun Yavuz, Unal Mehmet

Archives of Metallurgy and Materials

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2022

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Vol. 67, iss. 3

889-900

EN

In this study, microstructure, mechanical, corrosion and corrosive wear properties of Mg-xAg the as-cast and extruded alloys (x: 1, 3 and 5 wt.%Ag) were investigated. According to the experimental results, as the amount of Ag added in the casting alloys increases, the secondary phases (Mg4Ag, Mg54Ag17) emerging in the structure have become more clarified. Furthermore, it was observed that as the amount of Ag increased, the grain size decreased and thus the mechanical properties of the alloys increased. Similarly, the extrusion process enabled the grains to be refined and the mechanical properties to be increased. As a result of the in vitro tests performed, the Mg-1Ag exhibited very bad corrosion properties compared to other alloys. On the other hand, according to corrosive wear tests results, a high wear rate and friction coefficient were found for Mg-5Ag alloys.

2

Infuence of heat treatment (routes) on the microstructure and mechanical properties of 300M ultra high strength steel

Kasana Shivraj Singh, Sharma Sandeep, Pandey O. P.

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e126

EN

The study covered investigation of heat treatment (routes) effect on heat treatment of 300M ultra high strength steel to achieve the desired microstructure and the corresponding mechanical properties. 300M steel was prepared and subjected to diferent homogenization and forging processing. Structure-property relationship was established for both conventional and heat treatment route as well as isothermal and modifed route. Micrographs of 300M steels indicated that the isothermal heat treatment provided higher volume of retained austenite along with martensite and bainite. X-ray difraction (XRD) revealed that the dislocation density of isothermally heat-treated 300M steels was higher than the conventional steel. Isothermally heat-treated 300M samples have shown improved elongation and impact strength with the marginal loss of yield strength and ultimate tensile strength. Yield strength (1605 MPa), ultimate tensile strength (1890 MPa), impact strength (28 J), and percentage elongation (22%) of the isothermally heat-treated samples were comparable to the specifcations of the customer i.e., minimum yield strength 1480 MPa, ultimate tensile strength 1803 MPa, percentage elongation 7% and impact strength at −40 °C of 20 J, respectively. The SEM analysis of tensile and impact fractured surfaces revealed the large number of dimples which indicate the good ductility and toughness in the isothermally heat-treated samples.

3

Biomaterials for hip implants – important considerations relating to the choice of materials

Choroszyński M., Choroszyński M. R., Skrzypek S. J.

Bio-Algorithms and Med-Systems

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2017

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Vol. 13, no. 3

133--145

EN

This article is a review of important material requirements for hip biomaterials including their response to the body environment (biocompatibility), mechanical properties, wear resistance, fretting corrosion and availability as well as the price. The application of proper biomaterials for hip implants is one of the major focal points in this article. Background information is also provided on metals used in other prosthetic devices and implant components. Titanium and its alloys, cobalt base alloys and stainless steels (bio-steels) are used for load-bearing hip implants. These three groups of metallic materials will be introduced and discussed in detail. Metals and their alloys are crystalline materials since their properties depend on the crystal lattice, chemical and phase compositions, grain size, lattice defects, crystalline texture and residual microand macro-stresses. All these features of biomaterials are formed during technological manufacturing, such as metallurgical process, solidification, plastic deformation (rolling and forging), machining, heat treatment and coating. All these technological processes work in optimal conditions in order to achieve the optimal microstructure and mechanical, chemical and biological properties. Amongst the above-mentioned particular properties of biomaterials, fretting is a major concern as regards hip implants at the femoral head and neck taper interface. Additional important mechanisms of interaction between the implant and the human body must be taken into account, i.e. diffusion stream of foreign particles and atoms from the implant to body fluids, to the tissue and to the bone. These foreign particles and atoms are released from the implant to the body fluid, to the tissue and to the bone as wear product during use. All together they contribute to the wear, i.e. loss of weight, strength or volume of hip components. Wear rates of ultrahigh molecular weight polyethylene mated against Ti-6Al-4V are significantly greater than the ones for Co-Cr-Mo alloys. Therefore, thermochemical surface treatments like diffusion ion nitriding should be applied to increase the resistance of titanium alloys to wear. Austenitic stainless steels are also used for temporary applications, but they have lower resistance to pitting corrosion than titanium and cobalt alloys. The purpose of the paper is to introduce a group of metallic materials, which is often chosen for surgical hip implants. Conclusions of the paper refer to information which support important medical and patient decisions on hip implants. Also, the development of biomaterials, their treatments, properties, surface layers and coatings are considered. All these features develop over time and need synergy and experience in the progress of the biomedical, mechanical and materials science.

4

Nadmiarowe fazy w wysokoazotowych stalach austenitycznych

Kaputkina L., Svjażin A., Siwka J., Prokoszkina W.

Hutnik, Wiadomości Hutnicze

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2007

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Vol. 74, nr 7

357-363

PL

Badano zmiany zawartości azotu w austenicie po nagrzewaniu próbek do różnych temperatur i ich wygrzewaniu w różnych czasach. Ustalono, że w warunkach typowego nagrzewania w celu przesycenia bazowej stali Crl8Nil0Ti w jej strukturze występują nie rozpuszczone w roztworze starym azotki, których ilość zwiększa się ze wzrostem zawartości azotu w stali. Jest możliwe prawie całkowite rozpuszczenie się azotków przez nagrzanie metalu do temperatury 1200 °C i wygrzewanie go przez czas dłuższy niż 30 min. Zawartość azotu w austenitycznych stalach wysokoazotowych powinna być zbilansowana z zawartością innych pierwiastków stopowych w zależności od pożądanej struktury: austenit lub austenit i fazy nadmiarowe.

EN

Variations in the nitrogen content of austenite after heating the specimens up to different temperatures and then soaking them for different periods of time were investigated. It has been found that, under the conditions of typical heating to supersaturate the base Cr18Ni10Ti steel, nitrides undissolved in the solid solution occur in its structure, the amount of which increases with increasing nitrogen content of steel. Almost complete dissolution of nitrides is possible by heating the metal up to a temperature of 1200 °C and then soaking it for a period of time not longer than 30 min. The nitrogen content of high-nitrogen austenitic steels should be balanced with the contents of other alloy-forming elements, depending on the desired structure: austenite or austenite and excess phases.

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Betony samozagęszczalne, wpływ mikrowypełniaczy na mikrostrukrurę i właściwości

Grzeszczyk S., Podkowa P.

Zeszyty Naukowe. Budownictwo / Politechnika Opolska

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2005

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z. 48

45-57

PL

W pracy przedstawiono wyniki badań wpływu dodatków do cementu w postaci popiołów lotnych i mączki wapiennej na właściwości i mikrostrukturę betonów samozagęszczalnych. Wykazano, że samozagęszczalne mieszanki betonowe zawierające mączkę wapienną jako mikrowypełniacz wykazują mniejszy stopień upłynnienia, dlatego do uzyskania upłynnienia charakterystycznego dla mieszanek samozagęszczalnych wymagają one większej ilości wody i superplasyfikatora niż mieszanki betonowe zawierające popioły lotne. Betony samozagęszczalne zawierające jako mikrowypełniacz mączkę wapienną charakteryzują się większą wodoprzepuszczalnością i wykazują mniejszą odporność na działanie mrozu i środków odladzających, przy czym wzrost stopnia rozdrobnienia mączki wapiennej wpływa na poprawę tych parametrów. Na podstawie przeprowadzonych badań mikrostruktury próbek betonów wykazano, że mniejsza odporność betonów samozagęszczalnych zawierających jako mikrowypełniacz mączkę wapienną na działanie mrozu i soli odladzającej jest związana ze zwiększonym udziałem porów kapilarnych oraz występowaniem dużych kryształów hydratów w mikrostrukturze tych betonów.

EN

In this work, results of investigations on the effect of fly ash and limestone micro-fillers on the properties and microstructure of self-compacting concretes have been re-ported. SCC mixtures containing the limestone microfiller have proved to show lower fluidity degree therefore to achieve fluidity required for SCC mixture they need higher amount of water and superplasticizer than those including fly ash. SCCs with the limestone microfiller are characterized by higher water-permeability and lower resistance both to frost and deicing agents, whereas an increase in the limestone flour fineness leads to improvement of these parameters. From the studies carried out on the micro-structure of conerete samples it was found that the lower resistance to frost and deicing salt of SCCs containing the limestone microfiller is related to a higher share of capillary pores and occurrence of large hydrate crystals within the microstructure of these concretes.