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Benefit Effect of Low Addition Yttrium on the Phase αMg and eutectic αMg+γ(Mg17Al12) in AZ91 Alloy

Mikusek D., Rapiejko C., Andrzejczak A., Pacyniak T.

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 1

57--63

EN

This paper presents results of a study of the effect of inoculation of yttrium on the microstructure of AZ91 alloy. The concentration of the inoculant was increased in samples in the range from 0.1% up to 0.6%. The influence of Y on the thermal effects resulting from the phase transformations occurring during the crystallisation at different inoculant concentrations were examined with the use of Derivative and Thermal Analysis (DTA). The microstructures of the samples were examined with the use of an optical microscope; and an image analysis with a statistical analysis were also carried out. Those analyses aimed at examining oh the effect of inoculation of the Y on the differences between the grain diameters of phase αMg and eutectic αMg+γ(Mg17Al12) in the prepared examined material as well as the average size of each type of grain by way of measuring their perimeters.

2

Experimental and numerical analyses of 45 steel during three dimensional severe plastic deformation (3D-SPD)

Pang Yuhua, Lin Pengcheng, Sun Qi, Zhang Zhe, Liu Dong

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

71--81

EN

Due to the limitation of huge forming load, inhomogeneity of plastic deformation, and small volume of deformation region, it is difficult to prepare bulk ultra-fine grains material (UFGM) with industry size by the existing severe plastic deformation (SPD) methods. In this study, a novel SPD method, namely 3D-SPD, was proposed. By establishing finite element model, the distribution of material flow, restraining to Mannesmann effect, and comparison of load were discussed. Based on the self-developed rolling mill, the corresponding experiments were conducted. The experimental results reveal that the buck ultra-fine grains material of 45 steel was obtained under the condition of feed angle 21°, cross angle 15°, cone angle 5°, reduction rate 50%, and roll speed 30 rpm. The average grain size was refined from 46 to 0.8–4 μm. The tensile test results indicate that the yield strength and tensile strength of the rolled bar were significantly improved.

3

Competitive Nucleation in Grey Cast Irons

Arab N.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 4

185--189

EN

Cast irons are good examples of materials which are more sensitive to chemical composition and production conditions. In this research to improve casting quality, solidification and nucleation process in grey cast iron was investigate. In particular, attempts have been made to rationalize variation in eutectic cells with nucleation sites and eutectic solidification undercooling. Four castings with different diameter and similar chemical composition and pouring temperature and different inoculant percentage was casted. The cooling curve and maximum and minimum undercooling for each castings was measured. Also optical metallography and image analyzer has been used to determine the average eutectic cells diameter, and linear and surface densities, and volume density was calculated. The results of this research show a competitive behavior between nucleation sites and eutectic undercooling. Higher nucleation sites and higher eutectic undercooling cause higher eutectic cell density. But increasing nucleation sites by introducing inoculants to molten metal, is accompanied with reduction in eutectic undercooling. It means that inoculation and undercooling have opposite effect on each other. So, to achieve maximum cell density, it is necessary to create an optimization between these parameters.

4

Mechanical and microstructural properties of Mg-based AZ31 alloy processed by ARB

Palán J., Kubina T., Köver M., Slama P.

Archives of Materials Science and Engineering

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2015

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Vol. 76, nr 2

129--133

EN

Purpose: Severe plastic deformation techniques are known to produce materials with ultrafine-grained structures and enhanced mechanical properties. In magnesium alloys, these techniques improve both strength and ductility, as the latter is normally low at room temperature. In the present experiment, properties of rolled products after two rolling passes were examined. Rolling was carried out at 350°C and 400°C. At 350°C, the rolled sheets did not bond. Mechanical properties of the rolled products were determined. Microhardness profiles were measured to map the deformation distribution. The impact of the number of passes on mechanical properties was evaluated. It was found that with increasing number of passes, ultimate strength yield strength improve, and elongation does not decrease. Metallographic examination of the rolled products was carried out to assess the quality of the resulting joint. In certain locations, the joint was not distinctly visible, which proves its high quality. Design/methodology/approach: The evaluation was performed by simple tensile testing and light microscopy. The first conclusions were derived from the determined mechanical properties and based on analogies in available publications on a similar topic. Findings: This study confirmed that the SPD process improves mechanical properties and does not impair the ductility of the material. With increasing number of passes, the mechanical properties of the sample become more uniform.

5

Wpływ zabiegu modyfikowania zaprawą ZnTi3,2 na mikrostrukturę stopu ZnAl10

Piwowarski G., Buraś J., Krajewski W. K.

Archives of Foundry Engineering

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2013

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Vol. 13, iss. 3 spec.

129--132

PL

Publikacja dotyczy zabiegu modyfikowania podwójnych stopów Zn o średniej zawartości aluminium dodatkiem zaprawy zawierającej tytan i obejmuje badania wpływu zabiegu modyfikowania na stopień rozdrobnienia mikrostruktury stopu Zn-10% mas. Al (ZnAl10) odlewanego do formy piaskowej. Badany stop został rozdrabniany zaprawą modyfikującą Zn – 3,2% mas. Ti, wprowadzającą do metalu Ti. Na podstawie dokonanej oceny obrazów mikrostruktury stopu wyjściowego niemodyfikowanego i zmodyfikowanego zmiennym dodatkiem Ti zawartego w zaprawie modyfikującej stwierdzono, że zastosowana zaprawa modyfikująca powoduje określone, w zależności od ilości wprowadzonego do stopu Ti, rozdrobnienie ziarna stopu w stosunku do stopu wyjściowego niemodyfikowanego. Z kolei wyniki uzyskane w przeprowadzonej analizie termicznej potwierdzają zarodkotwórcze działanie użytej do badań zaprawy.

EN

The paper deals with grain-refinement of the sand-cast binary medium-aluminium Zn-10 mas. % alloy (ZnAl10) by using the Zn-3.2 mas. %Ti master alloy. Basing on the structure analysis it was stated that the master alloy causes significant grain-refinement in comparison with the initial, no modified alloy. Thermal analysis of the cooling curves stated that the modified alloys had increased nucleation temperatures and, at the same time, decreased recalescence – which proves nucleating action of the Zn-3.2 mas. %Ti master alloy in the examined alloy.

6

Strain-Stress Conditions of Shear Band Formation during CEC Processing on a New MachinewithControl Back-Pressure

Richert J.

Archives of Metallurgy and Materials

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2010

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Vol. 55, iss. 2

391-408

EN

The results of experimental investigations of the CEC processes, performed on a new special hydraulic press with control back-pressure, are presented for the first time. Due this very advantageous conditions of plastic deformation very interesting and unique experimental results, enabling accurate determination of the directions of shear bands formation were obtained. It has been observed that after very large plastic deformation of the solution heat-treated 6082 alloy, taking squares in the presence of high hydrostatic pressure, he the surface of the deformed samples an easily noticed relief is formed, resulting from the formation of numerous intersecting shear bands. It has been found that under conditions of hydrodynamic lubrication, all shear bands are formed at the angle of 45° this the extrusion direction and their intersection occurs at the angle of 90°. Such mechanism of shear bands formation allowed determining the true state of strain and stress, occurring in the deformation zone of the CEC processes.

PL

W niniejszej pracy po raz pierwszy przedstawiono wyniki badań eksperymentalnych procesów cyklicznego wyciskania (CWS) przeprowadzonych na nowej, specjalnej prasie hydraulicznej z kontrolowanym przeciwciśnieniem. Dzięki zapewnieniu bardzo korzystnych warunków odkształcania plastycznego uzyskano interesujące i unikalne wyniki badań eksperymentalnych, pozwalające na wyraźne ujawnienie kierunków tworzenia pasm ścinania. Mianowicie stwierdzono, że po bardzo dużych odkształceniach plastycznych przesyconego stopu 6082, realizowanych w obecności wysokiego ciśnienia hydrostatycznego, na powierzchni odkształconych próbek powstaje łatwo zauważalny relief pochodzący od tworzenia się licznych, wzajemnie przecinających się pasm ścinania. Stwierdzono, że w przypadku zastosowania bardzo dobrych warunków smarowania narzędzi, wszystkie pasma ścinania tworzą się pod kątem 45° do kierunku wyciskania, a ich wzajemne przecinanie zachodzi pod kątem 90°. Taki mechanizm tworzenia pasm ścinania pozwolił na określenie rzeczywistego stanu odkształcenia i naprężenia, wystepującego w kotlinie odkształcenia procesów CEC.