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Wykorzystanie wiązki jonów Ga+ do wycinania preparatów

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Mikroskopia transmisyjna, umożliwiająca prowadzenie charakterystyki mikrostruktury, lokalnego składu fazowego i chemicznego w skali atomowej, zajmuje centralne miejsce wśród technik wykorzystywanych do badań materiałów [1]. Pomimo wielu zalet technika ta jest jednak stosunkowo rzadko wykorzystywana, zarówno ze względu na stopień komplikacji mikroskopów, jak i problemy z przygotowaniem prepar[...]

Transformation of Ti/Al multilayers to the Ti3Al phase aimed at bonding of titanium alloys DOI:10.15199/28.2016.5.4


  The freestanding Ti/Al multilayer (with 3:1 the chemical composition ratio) was applied to bond the parts from Ti-6Al-4V alloy. The as-deposited multilayer and the joint obtained with it were characterized with the use of transmission electron microscopy (TEM) method including selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDS). It was observed that the annealing at 800°C for 1 h in vacuum of 1 Pa helped to transform Ti/Al multilayer into fine grains (grain size < 1 μm) of Ti3Al acting as a filler material between pieces of Ti-6Al-4V. The resulting joint shows generally good connection with the presence of small porosity both at the filler material/Ti-6Al-4V base material interface (larger) and on the Ti-6Al-4V side (smaller). Additionally, near surface zone of the joint, the parts were strongly depleted of aluminium. Key words: diffusion bonding, Ti/Al multilayers, Ti-6Al-4V alloys, TEM, EDS.1. INTRODUCTION Heating of Ti/Al multilayers could result in the formation of various titanium aluminides, such as Al3Ti, Ti3Al or TiAl. Due to negative enthalpy of mixing their formation is accompanied by a strong exothermic effect [1, 2]. The type of a final product depends on the bilayer thickness ratio, i.e. averaged multilayer chemical composition. However, slow heating of the whole multilayer causes that the reaction is controlled through a solid state diffusion (SSD) across neighboring interfaces being an example of one of phase transformations in solid state [3]. The level and extent of the local intermixing, both increasing with lowering of the multilayer period, decides on the phase precipitation sequence taking place during this process [4]. Fast local temperature rise leads to a reaction known as self-propagating hightemperature synthesis (SHS) occurring along the multilayers in the form of roughly planar front. In Ti/Al multilayers it is accompanied by melting of aluminium layers and conseque[...]

Application of TiN/Si3N4 nanocomposite surface layers in duplex coatings on stainless and high speed steels

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The TiN/Si3N4 layers ware deposited on nitrided 316L stainless steel and SW7M high speed steel to form duplex coatings. The 316L was glow discharge nitrided at 450, 460 and 550oC respectively, while SW7M was nitrided at 450oC. The TiN/Si3N4 was formed with magnetron reactive sputtering using TiSi4 (at. %) target and substrate was kept at ~300oC. The microstructure observations indicated that [...]

Effect of MgO single crystal orientation on microstructure of reaction products formed in liquid Al/MgO couples

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Aluminium is a common alloying addition in many industrially important high temperature alloys, while MgO is either main constituent or sintering aid in advanced refractories used in melting and casting of such alloys. Thus information on reactivity in Al/MgO system is of a great practical importance. Furthermore, knowledge on interaction at the Al/MgO interface is vital for understanding the mechanism of in-situ synthesis of DIMOX (Direct Matrix Oxidation) type composites, i.e. Al-Al2O3 [1, 2]. The early wetting experiments [3?€6] performed in vacuum with Al/MgO system showed that liquid Al reacts with MgO to form inside the substrate a thick reaction product region (RPR). Both its thickness and structure were found to depend on substrate structure (monocrystalline or polycrystalline, crystallographic orientation). Mcevoy et al. [3] suggested the formation of MgAl2O4 inside the RPR, while Fujii and Nakae [4] reported Al2O3. However, the more recent study of the group led by Fujii [5] clearly evidenced that both MgAl2O4 and Al2O3 phases can be formed. Simultaneously, they claimed that the type of alumina formed in RPR depends on the substrate orientation, i.e. ?ż-Al2O3 for (100) MgO and ?Č?Ś- ?Č- and ?Â-Al2O3 for (110) MgO and (111) MgO, respectively. Our experiments involving [100], [110] and [111] MgO substrates showed that in all cases, the reaction starts with the formation of Al2O3 separated by Al channels [6?€8]. Only in later stages, locally the layer composed of MgAl2O4 and Al starts to form as well [6, 7]. The analysis of the electron diffraction patterns acquired from the Al2O3 crystallites indicated that they were always of the same corundum ?ż-Al2O3 type, independently of substrate orientation. The characterization of RPR microstructure in the Al/MgO is as important as phase identification but the former so far gained much less attention. The early investigation performed with the help of optical micros[...]

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