Wyniki wyszukiwania - Biblioteka Nauki

1

Negative Stiffness Demonstrated by NiAl Nanofilms

100%

Babicheva R. I. , Bukreeva K. A. , Dmitriev S. V. , Mulyukov R. R. , Zhou K.

Computational Methods in Science and Technology

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2013

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tom Vol. 19, No. 3

127--135

EN

This paper studies the uniaxial strain control tension of NiAl nanofilms via molecular dynamics simulations. The nanofilm deforms elastically until fracture at tensile strain is as large as 37%. The stress-strain curve has a range where tensile deformation develops at decreasing tensile stress, thus indicating negative stiffness. Such deformation is thermodynamically unstable and the nanofilm splits into domains with two different values of elastic strain. Deformation within the unstable range is controlled by motion of the domain walls, resulting in the domains with larger strain grow at the expense of the domains with smaller strain.

2

Microstructural investigation and wear characteristics of Al-Si-Ti cast alloys

88%

Subhi A. D. , Khleif A. A. , Abdul-Wahid Q. S.

Engineering Transactions

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2020

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tom Vol. 68, iss. 4

385--395

EN

Hypoeutectic Al-7Si alloys containing various titanium proportions (0.8–1.6%) were produced and analyzed in this work. The wear characteristics of Al-Si alloys were studied under the conditions of dry sliding at various applied loads. Optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to depict the microstructure, worn surface and phases, respectively. Phases of -Al, eutectic and Ti9Al23 were recognized in the Al-Si-Ti alloys matrix. Considerable coarsening took place in -Al and eutectic silicon in a fully eutectic through solidification. The hardness was increased as the titanium proportion increased. Furthermore, significant changes were found in the wear rate depending on the titanium proportion added and load applied.

3

Growth of intermetallic compound between indium-based thermal interface material and copper substrate: molecular dynamics simulations

75%

Fałat T. , Płatek B.

Materials Science Poland

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2015

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tom Vol. 33, No. 2

445--450

EN

The diffusion phenomenon occurring between copper and indium was investigated by molecular dynamics simulations. The calculations were carried out in various temperatures in aging domain with the use of the commercially available Materials Studio v.6. software. The results showed that the intermetallic compound (IMC) growth followed the parabolic law, which indicated this growth to be mainly controlled by volume diffusion. The growth activation energy was estimated at 7.48 kJ.mol(-1).

4

Investigation of properties of Cu-Al explosively welded bimetals

63%

Lokaj J. , Sahul M. , Sahul M. , Nesvadba P.

Materiały Wysokoenergetyczne

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2019

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tom T. 11(2)

31--37

EN

Explosion welding of cooper C10200 to AW 5083 aluminium alloy was performed. The C10200 was proposed as a flyer plate. A parallel setup was used during explosive welding. Bimetals were characterized by regular wavy interface. The intermetallic compound (IMC) layer was observed at the interface of bimetals after 12 month, however, no annealing was performed. EDX analyses revealed that the interface layer consists of the intermetallic compound CuAl. Microhardness at the interface increased due to the presence of the IMC and work hardening as well.

PL

Przedstawiono wyniki zgrzewania wybuchowego miedzi C10200 ze stopem aluminiowym AW 5083. Płytka wykonana z miedzi C10200 była elementem napędzanym. Zgrzewanie wybuchowe prowadzono równolegle na dwóch stanowiskach. Otrzymane bimetale charakteryzowały się regularną falistą powierzchnią łączenia. Badania warstwy związku międzymetalicznego, w obszarze połączenia bimetalicznego, przeprowadzono po upływie 12 miesięcy, jednakże bez wyżarzania. Analiza EDX wykazała, że warstwa łącząca składa się z związku międzymetalicznego CuAl. Mikrotwardość w obszarze łączenie wzrasta zarówno w wyniku obecności związku międzymetalicznego, jak i przeprowadzonego zgrzewania.

5

Wpływ mikrododatków na właściwości elektryczne miedzi

63%

Romanowska J. , Wnuk G. , Brydak K.

Zeszyty Naukowe Politechniki Rzeszowskiej. Elektrotechnika

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2005

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tom z. 28 [223]

143-146

PL

W pracy przedstawiono wstępne wyniki badań procesu usuwania arsenu ze stopów miedzi, metodą wprowadzania mikrododatków które łączą się z arsenem tworząc związki międzymetaliczne oraz wpływ tych związków na wybrane właściwości elektryczne miedzi. Dodanie do stopu Cu-As cyrkonu powodowało powstanie związków międzymetalicznych oraz znaczne zmniejszenie rezystywności stopu Cu-As-Zr. Wyniki pomiarów rezystywności badanych stopów odniesiono do właściwości czystej miedzi oraz przedstawiono zdjęcia mikroskopowe struktur badanych stopów.

EN

The method of removing arsenic from cooper by implementing microadditions which form intermetalic compounds with arsenic and the influence of these compounds on the electric properties of cooper has been presented in this paper. Zirconium added to theCu-As alloy caused the formation of intermetalic compounds and the decrease of the resistance of the Cu-As-Zr alloy. The results of the resistance measurements of the investigated alloys were compared with the electric properties of pure cooper. Moreover, the structures of the investigated alloys have been presented.

6

Fractographic and structural peculiarities of laser weld-on layers with a maraging alloy

63%

Shtarbakov V. , Stavrev D.

Archives of Materials Science and Engineering

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2015

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tom Vol. 75, nr 1

12--17

EN

Purpose: Purpose of the present paper is to investigate the fractographical peculiarities of the layers welded-on the surface of 30CrMoV12-28 (DIN) tool steel by laser with additional material of marraging alloy. Design/methodology/approach: The operation was accomplished on an AL 200 automatic weld-on machine with an Nd:YAG pulse resonator providing a beam of 1064 nm wavelength. The mean power output of the pulse was 200 W and the maximum peak power output was 10 kW. The operating frequency was 20 Hz. The diameter of the laser beam focused on the sample surface was 0.6 mm. The weld-on maraging alloy featured contents of 0.02C - 0.2Si - 0.2Mn - 2Cr - 19.3Ni - 0.4V - 4.7Mo - 14.5Co - 0.25Al, wt%. Studied were the fractures obtained at three - point bending of the layer upon weld-on followed by two - hour age hardening at temperatures of 550 and 600°C. Findings: The nature of deformation along the weld-on layer under tensile impact strains was studied, the destruction being trans-crystalline determined by the prevailing plastic deformation.The destruction after age hardening at temperatures of 550 and 600°C was of the mixed and trans-crystalline type. The results of the processes of dispersion hardening and those of the beginning of coherent phase formation were connected with the main matrix of the inter-metallic compounds based on NiAl and NiMo. The condition of the structure was characterized by the so called “pit” curved surface of the destruction. The analysis of the fractures along with the EDS analysis showed that the inter-metallic phases formed in the process of secondary hardening of the material in the weld-on layer were of the NiAl, NiMo and Ni3Mo type. Research limitations/implications: For more correct determination of phase contents in depth of hardened layers have to be used XRD techniques. Practical implications: Taking into account the high value of the materials used for producing press-forming dies it is of vital importance to find possibilities for considerable increase of the lifecycle of casting moulds. Laser surface welding-on by using of maraging alloy as additional material is cost effective technology for repairing of press-forming dies.

7

Vacuum brazing of TiAl48Cr2Nb2 casting alloys based on TiAl (γ) intermetallic compound

63%

Mirski Z. , Różański M.

Archives of Foundry Engineering

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2010

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tom Vol. 10, iss. 1 spec.

371--376

EN

A growing interest in modern engineering materials characterised by increasingly better operational parameters combined with a necessity to obtain joints of such materials representing good operation properties create important research and technological problems of today. These issues include also titanium joints or joints of titanium alloys based on intermetallic compounds. Brazing is one of the basic and sometimes even the only available welding method used for joining the aforesaid materials in production of various systems, heat exchangers and, in case of titanium alloys based on intermetallic compounds, turbine elements and space shuttle plating etc. This article presents the basic physical and chemical properties as well as the brazability of alloys based on intermetallic compounds. The work also describes the principle and mechanisms of diffusion-brazed joint formation as well as reveals the results of metallographic and strength tests involving diffusion-welded joints of TiAl48Cr3Nb2 casting alloy based on TiAl (γ) phase with the use of sandwich-type layers of silver-based parent metal (grade B- Ag72Cu-780 (AG 401)) and copper (grade CF032A). Structural examination was performed by means of light microscopy, scanning electron microscope (SEM) and energy dispersion spectrometer (EDS). Furthermore, the article reveals the results of shear strength tests involving the aforementioned joints.

8

Efect of heat treatment parameters on microstructure evolution, tensile strength, wear resistance, and fracture behavior of Ni-Ti multilayered composites produced by cross‑accumulative roll bonding

51%

Ye Q. , Li X. , Tayyebi M. , Assari A. H. , Polkowska A. , Lech S. , Polkowski W. , Tayebi M.

Archives of Civil and Mechanical Engineering

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2023

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tom Vol. 23, no. 1

art. no. e27, 2023

EN

The last decades have seen a huge growth in the investigation of intermetallic compounds at the interfaces of laminated composites due to their useful features. In this research, efects of the formation of intermetallic compounds on tensile properties and wear resistance of Ni/Ti composites produced by cross-accumulative roll bonding (CARB) process have been examined at diferent annealing times and temperatures. Scanning electron microscopy (SEM) images demonstrated that the layers were well bonded together, but Ni layers experienced instabilities in light of plastic deformation. The EBSD results showed lamellar structure and crystallographic texture on Ti and Ni layers during plastic deformation. According to X-ray difractometer (XRD) and energy-dispersive spectrometer (EDS) analyses, NiTi2 and NiTi were present in all annealed samples. The thickness of intermetallic compounds grew with an increase in annealing temperature and time. However, this growth led to a decrease in tensile strength while the values of elongation fuctuated. Based on the results of the wear test, the composite became more resistant to wear when the thickness of intermetallic layers increased. The surfaces of these layers with less roughness and lower coefcients of friction facilitated the movement of steel pin on samples during the wear test. Furthermore, wear mechanisms of adhesion, abrasion, and delamination were observed, and they were more noticeable at higher loads and lower annealing temperatures and times.

9

Wpływ obróbki cieplnej na odporność korozyjną elektrolitycznych powłok niklu z tytanem, molibdenem lub wanadem

51%

Panek J. , Budniok A.

Kompozyty

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2005

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tom R. 5, nr 3

62-69

PL

Elektrolityczne warstwy kompozytowe Ni+Me (Me = Ti, Mo, V) otrzymano drogą osadzania niklu z elektrolitu zawierającego zawiesinę proszku molibdenu, tytanu lub wanadu. Warstwy osadzano na podłożu stalowym (St3S) w warunkach galwanostatycznych. Do badań korozyjnych wybrano warstwy zawierające porównywalną ilość składnika proszkowego: około 20% at. Badania składu fazowego osadzonych warstw Ni+Me, przeprowadzone metodą dyfrakcji promieni rentgenowskich, wykazały, że składają się one z krystalicznej fazy niklu i wbudowanego molibdenu, tytanu lub wanadu (rys. 1a-c). Charakterystykę morfologii powierzchni oraz zgładów poprzecznych warstw, przed i po obróbce cieplnej, przeprowadzono za pomocą mikroskopu skaningowego (rys. rys. 2 i 3). Stwierdzono, że wprowadzenie proszku molibdenu, tytanu lub wanadu do elektrolitycznej osnowy niklowej powoduje otrzymanie warstw charakteryzujących się dużym rozwinięciem i bogatą topografią powierzchni. Obecność skupisk elektrolitycznego niklu osadzonych na powierzchni wbudowanych cząstek proszku metalicznego potwierdza adsorpcyjny mechanizm osadzania tych warstw. Obróbkę cieplną warstw kompozytowych prowadzono w próżni w zakresie temperatur 800:950°C w zależności od rodzaju warstwy. Obróbka ta prowadzi do zmian morfologii powierzchni i składu fazowego warstw. W wyniku zachodzącej reakcji w stanie stałym w warstwie Ni+Ti powstaje faza międzymetaliczna Ni3Ti, w warstwie Ni+Mo tworzy się związek Ni3Mo oraz roztwór stały molibdenu w niklu, a w warstwie Ni+V - jedynie roztwór stały wanadu w niklu (rys. 1d-f). Badania korozyjne warstw kompozytowych prowadzono w środowisku alkalicznym (5M KOH), Miarą odporności korozyjnej warstw były wartości potencjału i prądu korozyjnego - Ekor i jkor, wyznaczone metodą Sterna, a także wartość oporu polaryzacji - Rp i zużycia korozyjnego w mm/rok (tab. 1). Wyznaczone wartości tych parametrów porównywano z wartościami uzyskanymi dla osnowy niklowej. Stwierdzono, iż zmiany składu fazowego i morfologii powierzchni powstałe w wyniku obróbki cieplnej warstw powodują wzrost odporności korozyjnej, czego dowodem są niższe wartości prądu i zużycia korozyjnego, a także wzrost wartości potencjału korozyjnego i oporu polaryzacji. Najwyższą odporność korozyjną wykazywała warstwa Ni+Ti.

EN

Electrolytic composite layers Ni+Me (Me = Mo, Ti, V) were obtained by electrolytic deposition of nickel from an electrolyte containing Mo, Ti or V powder suspension. The layers were plated on steel base (St3S) under galvanostatic conditions. Corrosion tests were conducted on the layers containing comparable amount of incorporated metallic powder: about 20 at.%. The results of structural investigation of the obtained layers by the X-ray diffraction method show, that they consist in crystalline phase of nickel and incorporated Mo, Ti or V (Fig. 1a-c). Surface morphology of obtained layers as well as the cross-sectional images of obtained layers, before and after thermal treatment, were investigated by scanning microscope (Figs 2, 3). It was stated, that incorporation of metallic powder into the electrolytic nickel matrix causes the obtaining of layers characterized by great, developed surface area. The presence of electrolytical nickel nano-agglomerates plated on metallic powder particles confirms the adsorption mechanism of layers' deposition. Thermal treatment of Ni+Me composite layers was conducted in vacuum, at a temperature of 800:950°C, depending on the kind of layer. Thermal treatment changes the surface morphology and phase composition of the layers. As a result of solid-state reaction in Ni+Ti layer Ni3Ti intermetallic compound is arising. Thermal treatment of Ni+Mo layer leads to obtaining Ni3Mo phase and Mo(Ni) solid solution, whereas in Ni+V layer only V(Ni) solid solution is formed (Fig. 1d-f). Corrosion tests of Ni+Me composite layers were conducted in alkaline environment (5M KOH). As a measure of corrosion resistance served the corrosion potential and current values - Ekor and jkor, determined by Stern method, as well as the polarization resistance - Rp and the corrosion rate in nun/year (Tab. 1). The values of these parameters were compared to the values determined for nickel matrix. It was stated, that the changes of surface morphology and phase composition arising as a result of thermal treatment of the layers improved their corrosion resistance, what is confirmed by their lower corrosion current density and the corrosion rate, and by the higher values of corrosion potential and polarization resistance (Tab. 1). The highest corrosion resistance exhibits Ni+Ti layer.