Microstructure and plastic properties of mg-Li alloys smelted in vacuum induction furnaces after hot working

The paper analyses the characteristics of plasticity and microstructure of magnesium alloys with lithium meant for hot plastic working with different lithium content. The alloys were prepared in conditions of vacuum smelting. Achieved ingots were subject to hot extrusion. Tests on Gleeble simulator were conducted to assess the susceptibility of tested alloys to plastic forming in conditions of hot plastic working. For tested alloy the activation energy was marked for hot plastic deformation and plasticity characteristics in function of Zener-Hollomon parameter. After the analysis of the influence of temperature on the deformability of tested alloys it was stated that the alloy containing 8% Li (LAZ831) has better susceptibility to plastic treatment than alloy containing 4% Li (LAZ431), but higher than in case of classic magnesium alloys-AZ31.Web of Science6231432142

Blind gut perforation in the course of salmonellosis - case report

W pracy przedstawiono przypadek perforacji kątnicy w przebiegu infekcji wywołanej Salmonella species. Omówiono ryzyko powikłań chirurgicznych u chorych z salmonellozą.In the paper the case of caecum perforation due to Salmonella species infection was described. The risk of surgical complications in patients with salmonellosis was discussed

Study of hot deformation behavior of CuFe2 alloy

Nil strength temperature of 1062 degrees C and nil ductility temperature of 1040 degrees C were experimentally set for CuFe2 alloy. The highest formability at approx. 1020 degrees C is unusable due to massive grain coarsening. The local minimum of ductility around the temperature 910 degrees C is probably due to minor formation of gamma-iron. In the forming temperatures interval 650-950 degrees C and strain rate 0.1-10 s(-1) the flow stress curves were obtained and after their analysis hot deformation activation energy of 380 kJ.mol(-1) was achieved. Peak stress and corresponding peak strain values were mathematically described with good accuracy by equations depending on Zener-Hollomon parameter.Web of Science64270670

Ultrafine grain refinement of AlMn1Cu and AZ 31 alloys by SPD process

One of the ways to the more effective use of metallic materials is their processing by forming. At present in this the area the use of the process of severe plastic deformation (SPD process), leading to a refinement of the structure (materials with UFG structure) and thus to achievement of higher level of their utility value, is expanding. AlMn1Cu alloy is commercially produced aluminum alloy by the company Al Invest Bridlicna (the cast strip with a mild reduction by rolling up to 10% to the thickness of 10 and 15 mm, which has its uses especially in engineering. AZ31 alloy is commercially produced aluminum alloy after casting and extrusion at 400 C on final rod with 20 mm diameter. For experimental purposes from the belts of alloys the test samples of the underlying dimensions of 10 10 mm length 40 mm (geometry with channel deflection 20 ) and 15 15 mm length 60 mm (geometry with helix matrix) in the direction of rolling were made. All three instruments are made of high tool steel - HOTVAR. For compare the influence of geometry ECAP tool on structure refining was used AlMn1Cu and AZ31 alloys were used three specially made tools ECAP, differing mainly in the construction design.Web of Science59136435

Optymalizacja Procesu Walcowania Na Gorąco Aluminidku Fe-40at.%Al-Zr-B Na Podstawie Prób Laboratoryjnych

Use of the protective steel capsules enabled to manage the laboratory hot flat rolling of the extremely brittle as-cast aluminide Fe-40at.%Al-Zr-B with the total height reduction of almost 70 %. The hot rolling parameters were optimized to obtain the best combination of deformation temperature (from 1160°C up to 1240°C) and rolling speed (from 0.14 m·s−1 to 0.53 m·s−1). The resistance against cracking and refinement of the highly heterogeneous cast microstructure were the main criteria. Both experiments and mathematical simulations based on FEM demonstrated that it is not possible to exploit enhanced plasticity of the investigated alloy at low strain rates in the hot rolling process. The heat flux from the sample to the working rolls is so intensive at low rolling speed that even the protective capsule does not prevent massive appearance of the surface transverse cracking. The homogeneity and size of product’s grain was influenced significantly by temperature of deformation, whereas the effect of rolling speed was relatively negligible. The optimal forming parameters were found as rolling temperature 1200°C and the rolling speed 0.35 m·s−1. The effective technology of the iron aluminide Fe-40at.% Al-Zr-B preparation by simple processes of melting, casting and hot rolling was thus established and optimized.Zastosowanie ochronnych stalowych kapsuł pozwoliło na przeprowadzenie laboratoryjnego walcowania na gorąco pasm z niezwykle kruchego odlewanego aluminidku żelaza (stopu na osnowie fazy międzymetalicznej) Fe-40at.%Al-Zr-B, które umożliwiło redukcję wysokości o prawie 70%. Parametry walcowania na gorąco były dostosowywane celem uzyskania korzystnego zakresu temperatury odkształcenia (od 1160°C do 1240°C) oraz prędkości walcowania (od 0.14 m·s−1 do 0.53 m·s−1) dla otrzymania pasma bez pęknięć i rozdrobnienia silnie niejednorodnej mikrostruktury odlewu. Zarówno eksperymenty jak i matematyczne symulacje oparte na MES wykazały, że niemożliwe jest uzyskanie dobrej plastyczności badanego stopu przy niskich prędkościach odkształcenia podczas walcowania na gorąco. Strumień ciepła płynący z próbki na walce jest tak intensywny przy małej prędkości walcowania, że nawet kapsuła ochronna nie zapobiega pojawieniu się powierzchniowych pęknięć poprzecznych. Jednorodność i rozmiar ziarn w materiale silnie zależy od temperatury odkształcenia, podczas gdy wpływ prędkości walcowania jest relatywnie niewielki. Optymalne parametry kształtowania stopu to: temperatura 1200°C oraz prędkość walcowania 0.35 m·s−1. Skuteczna technologia przygotowania aluminidku żelaza Fe-40at.%Al-Zr-B w prostym procesie topienia, odlewania i walcowania na gorąco została w ten sposób ustalona i zoptymalizowana.Web of Science6031701169

A new model describing the hot stress–strain curves of HSLA steel at high deformation

; ;The torsion test is often applied for the determination of the hot flow stress of steels. An originally derived system of equations has been used to describe the basic parameters of the torsion test and has enabled precision to be obtained in the simulation of flat rolling. Because of the relatively low strain rates obtained with a torsion plastometer, it is necessary to extrapolate the laboratory results into the range of real working conditions. In this case, only a limited number of demanding and expensive interrupted tests have to be done. The more important role is then played by computer prediction based on equations that incorporate the results of simple, but mainly continuous tests. Examples of such mathematical models are presented, including the influence of dynamic or static softening in hot rolling

Strain-rate sensitivity in hot forming of steels - Influence of microstructure, temperature and chemical composition

A methodology to determine the strain-rate sensitivity index was developed, based on rolling of a set of samples with the same draught but different speed at defined temperatures. It was shown that initial grain size has nearly negligible influence on the investigated variable, in contrast to phase composition whose influence is very considerable. Combined influence of strain rate and temperature on deformation resistance of various types of steel was studied. For a selected group of steels a universal equation was set up, which described, with a good accuracy, impact of reciprocal temperature and chemical composition (expressed simply by nickel equivalent) on strain-rate sensitivity in hot state