Abstract:One of the major barriers limiting the suitability of TiAl intermetallic alloys for use in the demanding aircraft and automotive industries is their susceptibility to degradation as a result of oxidation at temperatures exceeding 760 • C. Paper presents the characteristics of resistance to cyclic oxidation at 950 • C for Ti-45Al-8Nb-0.5(B, C) alloy with and without protective coating obtained as a result of aluminizing using out of pack method. The characteristics of surface condition were determined by scanning electron microscope with EDS system, transmission electron microscope, and X-ray diffractometer. The favorable behavior of the Ti-45Al-8Nb-0.5(B, C) alloy with a protective coating under cyclic oxidation conditions is a result of a higher content of Al 2 O 3 in the microstructure of the scale and the presence of Al and Nb-rich phases at the substrate interface, which probably constitue a barrier for oxidation process. The high temperature oxidation test revealed that aluminide coating was responsible for a remarkable improvement in the oxidation resistance.
This paper presents the possibilities of forming the microstructure as well as mechanical properties and electrical conductivity of Cu-3Ti alloy (wt.%) in thermal and thermomechanical processes that are a combination of homogenising treatment, hot and cold working, solution treatment and ageing. Phase composition of the alloy following various stages of processing it into the specified semi-finished product was being determined too. It was demonstrated that the application of cold plastic deformation between solution treatment and ageing could significantly enhance the effect of hardening of the Cu-3Ti alloy without deteriorating its electrical conductivity. It was found that for the investigated alloy the selection of appropriate conditions for homogenising treatment, hot and cold deformation as well as solution treatment and ageing enables to obtain the properties comparable to those of beryllium bronzes.
In the paper, results of a study on the effects of deformation conditions (temperature, strain and strain rate) on flow curves, maximum flow stress and corresponding deformation of Cu-Ti alloys with various Ti contents, subjected to hot deformation, are presented. Evaluation of formability of alloys was performed with the use of a Gleeble HDS-V40 thermal-mechanical simulator during uniaxial hot compression at 700 to 900• C, strain rate of 0.1 to 10.0 s −1 and strain of 0 to 1.2 (70%). It was found that within the analysed ranges of temperature, strain rate and strain, Cu-Ti alloys underwent uniform deformation without cracking. The largest deformation resistances were observed for the alloys with the highest Ti contents; their decrease was possible with the temperature raise and the strain rate reduction.Keywords: copper-titanium alloy, hot compression test, plasticity, flow curves W pracy przedstawiono wyniki badań wpływu warunków odkształcenia (temperatura, wielkość i prędkość odkształcenia) na przebieg krzywych płynięcia, wartość maksymalnego naprężenia uplastyczniającego i odpowiadającego mu odkształcenia odkształcanych plastycznie na gorąco stopów Cu-Ti o zróżnicowanej zawartości Ti. Ocenę podatności do kształtowania plastycznego stopów przeprowadzono na symulatorze cieplno-mechanicznym systemu Gleeble HDS-V40 w warunkach jednoosiowego ściskania na gorąco w zakresie temperatury od 700 do 900• C, prędkości odkształcenia od 0.1 do 10.0 s −1 i odkształcenia od 0 do 1.2 (70%). Stwierdzono, że w analizowanych przedziałach temperatury, prędkości i wielkości odkształcenia stopy Cu-Ti odkształcają się w sposób jednorodny bez udziału pękania. Wykazano, że największe opory kształtowania plastycznego towarzyszą stopom o najwyższej zawartości Ti, a ich zmniejszenie jest możliwe poprzez podwyższenie temperatury i obniżenie prędkości odkształcenia.
In this paper, the technology of melting in induction furnaces with ceramic crucibles was used for production of TiAl-based Ti-47Al-2W-0.5Si alloy. Due to high reactivity of liquid titanium alloys, the melting process was conducted in special crucibles made of stabilised ceramic materials resistant to the aggressive action of these alloys. When characterising the chemical composition and microstructure of Ti-47Al-2W-0.5Si alloy melted in different ceramic crucibles, problems accompanying the melting process were described and conditions for making an alloy with satisfactory purity were determined.
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