16 research outputs found
Global warming accelerates the upfreezing of permafrost in arid middle Tianshan Mountains
Mikrostruktura stop贸w NiAlV poddanych odkszta艂ceniu metod膮 skr臋cania pod wysokim ci艣nieniem
Some attention in physical metallurgy is devoted to the mechanisms of decomposition of the disordered phases via eutectoid transformation accompanied by the atomic ordering. In case of the non-pearlitic modes of transformation this concerns intermetallic phases of the general description A3B-A3C. The application of intensive deformation like HPT may introduce opposite mechanisms introducing some degree of the metastable disordered phase structure at room temperature. The paper presents results of the phase composition and microstructure studies of the alloys of composition Ni75AlxVy (where x =15, 10, 5 and y =10, 15, 20), which undergo the solid-state eutectoid decomposition at temperature 1281 K, in the equilibrium conditions. The alloys achieved by the cold crucible levitation method were later intensively deformed with the method of high pressure torsion (HPT). The alloys after HPT revealed homogenous, metastable L12 (Ni3Al) structure in place of the eutectoid product L12-D022. The average size of the Sherrer鈥檚 coherent diffraction volumes did not exceed 9 nm, suggesting nano-structure of the material. Transmission electron microscopy (TEM) and high resolution electron microscopy (HRTEM) revealed that the micro- and nano- deformation twins were the main feature of the microstructure, dividing volume into cells of the sizes similar to the coherent volumes. The HPT deformation did not influence atomic order. The results are compared with those achieved for the injection cast samples.W publikacjach z zakresu fizycznej metalurgii przejawia si臋 zainteresowanie mechanizmami rozpadu, nie perlitycznego typu, faz nieuporz膮dkowanych, zachodz膮cymi z udzia艂em uporz膮dkowania atomowego. Dotyczy to faz rodzaju A3B-A3C. Zastosowanie intensywnego odkszta艂cenia metod膮 skr臋cania pod wysokim ci艣nieniem (HPT) mo偶e przeciwdzia艂a膰 rozpadowi wprowadzaj膮c fazy metastabilne, o pewnym stopniu nieuporzadkowania atomowego, w temperaturze pokojowej. Artyku艂 przedstawia wyniki bada艅 sk艂adu fazowego i mikrostruktury stop贸w o sk艂adzie Ni75AlxVy (gdzie x =15, 10, 5 i y =10, 15, 20), podlegaj膮cych, w warunkach r贸wnowagi, rozpadowi eutektoidalnemu w temperaturze 1281 K. Stopy otrzymano metod膮 lewitacji w zimnym tyglu (CCLM) a nast臋pnie poddano przer贸bce metod膮 intensywnego odkszta艂cenia skr臋caniem pod wysokim ci艣nieniem. Po takim procesie stopy wykazywa艂y jednorodn膮 struktur臋 L12 (Ni3Al), zamiast produkt贸w rozpadu eutektoidalnego w postaci struktur L12-D022. 艢redni rozmiar koherentnych obszar贸w rozpraszania Sherrera nie przekracza艂 9 nm, wskazuj膮c na materia艂 o charakterze nano-strukturalnym. Zastosowanie transmisyjnej mikroskopii elektronowej (TEM) i wysokorozdzielczej transmisyjnej mikroskopii elektronowej (HRTEM) pokaza艂o, 偶e bli藕niaki odkszta艂cenia o rozmiarach mikro i nano by艂y g艂贸wnymi elementami mikrostruktury, dziel膮c ca艂膮 obj臋to艣膰 na kom贸rki o rozmiarach podobnych do rozmiar贸w obszar贸w koherentnego rozpraszania. Metoda HPT nie wp艂yn臋艂a natomiast na uporzadkowanie atomowe. Wyniki por贸wnano z uzyskanymi dla pr贸bek otrzymanych metod膮 szybkiego ch艂odzenia przez wtryskiwanie do wlewnicy
Effect of pre-aging on the microstructure and strength of supersaturated AlZnMg alloys processed by ECAP
This work is focused on the effect of the combination of natural aging and severe plastic
deformation (SPD) produced by Equal-Channel Angular Pressing (ECAP) on the microstructure and
strength of supersaturated AlZnMg alloys. Following a solution heat-treatment and quenching into
water at room temperature, samples were naturally aged for different time periods and then
processed by ECAP. The microstructure and mechanical properties of these samples are described
and discussed. This investigation leads to proposing an interesting application of ECAP for
supersaturated alloys. Using the shear bands created by ECAP in only one pass and applying
appropriate subsequent aging treatments, composite-like microstructures can be achieved in
conventional age-hardenanble Al alloys