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

Technological Aspects of Production and Processing of Functional Materials Based on Intermetallic Fe-Al

The problems of this paper relate to a possibility to affect the structure and properties of new alloys with an intermetallic phase matrix of the Fe-Al system by improvements in casting and hot plastic working processes. The studies were focused on selection of an optimum chemical composition and parameters of the casting and heat treatment processes for further hot plastic working process. The primary goal was to obtain semifinished products in the forms of sheets and bars with specified set of mechanical and physical properties. The works included several selected alloys with various Al content and variable contents of alloying elements influencing the formation of intermetallic phases. A series of characteristics of mechanical, physical, and chemical properties of alloys containing 28 and 38% of Al were developed. The result of the work consists in the development of a technology for hot forming of flat and round products

Effects of equal channel angular pressing and heat treatments on the microstructures and mechanical properties of selective laser melted and cast AlSi10Mg alloys

This study investigated the impact of the equal channel angular pressing (ECAP) combined with heat treatments on the microstructure and mechanical properties of AlSi10Mg alloys fabricated via selective laser melting (SLM) and gravity casting. Special attention was directed towards determining the effect of post-fabrication heat treatments on the microstructural evolution of AlSi10Mg alloy fabricated using two different routes. Three initial alloy conditions were considered prior to ECAP deformation: (1) as-cast in solution treated (T4) condition, (2) SLM in T4 condition, (3) SLM subjected to low-temperature annealing. Light microscopy, transmission electron microscopy, X-ray diffraction line broadening analysis, and electron backscattered diffraction analysis were used to characterize the microstructures before and after ECAP. The results indicated that SLM followed by low-temperature annealing led to superior mechanical properties, relative to the two other conditions. Microscopic analyses revealed that the partial-cellular structure contributed to strong work hardening. This behavior enhanced the material's strength because of the enhanced accumulation of geometrically necessary dislocations during ECAP deformation.Web of Science213art. no. 9

Superplastic Deformation of Al–Cu Alloys after Grain Refinement by Extrusion Combined with Reversible Torsion

The binary as-cast Al–Cu alloys Al-5%Cu, Al-25%Cu, and Al-33%Cu (in wt %), composed of the intermetallic θ-Al2Cu and α-Al phases, were prepared from pure components and were subsequently severely plastically deformed by extrusion combined with reversible torsion (KoBo) to refinement of α-Al and Al2Cu phases. The extrusion combined with reversible torsion was carried out using extrusion coefficients of λ = 30 and λ = 98. KoBo applied to the Al–Cu alloys with different initial structures (differences in fraction and phase size) allowed us to obtain for alloys (Al-25%Cu and Al-33%Cu), with higher value of intermetallic phase, large elongations in the range of 830–1100% after tensile tests at the temperature of 400 °C with the strain rate of 10−4 s−1. The value of elongation depended on extrusion coefficient and increase, with λ increasing as a result of α-Al and Al2Cu phase refinement to about 200–400 nm. Deformation at the temperature of 300 °C, independently of the extrusion coefficient (λ), did not ensure superplastic properties of the analyzed alloys. A microstructural study showed that the mechanism of grain boundary sliding was responsible for superplastic deformation

Investigations of TiO₂, Ti/TiO₂, and Ti/TiO₂/Ti/TiO₂ coatings produced by ALD and PVD methods on Mg-(Li)-Al-RE alloys substrates

Magnesium alloys have recently become increasingly popular in many sectors of the industry due to their unique properties, such as low density, high specific strength, vibration damping ability along with their recyclability and excellent machinability. Nowadays, thin films have been attracting more attention in applications that improve mechanical and corrosion properties. The following alloys were used for the coated Mg-Al-RE and the ultra-light magnesium-lithium alloy of the Mg-Li-Al-RE type. A single layer of TiO2 was deposited using the atomic layer deposition ALD method. Multiple layers of the Ti/TiO₂ and Ti/TiO₂/Ti/TiO₂ type were obtained by the MS-PVD magnetron sputtering technique. Samples were investigated by scanning and a transmission electron microscope (SEM, TEM) and their morphology was studied by an atomic forces microscope (AFM). Further examinations, including electrochemical corrosion, roughness and tribology, were also carried out. As a result of the research, it was found that the best electrochemical properties are exhibited by single TiO2 layers obtained by the ALD method. Moreover, it was found that the Ti/TiO₂/Ti/TiO₂ double film has better properties than the Ti/TiO₂ film

Effect of various SPD techniques on structure and superplastic deformation of two phase MgLiAl alloy

MgLiAl alloy containing 9 wt% Li and 1.5% Al composed of hexagonal alpha and bcc beta phases was cast under protecting atmosphere and hot extruded. Various methods of severe plastic deformation were applied to study their effect on structure and grain refinement. Rods were subjected to 1-3 passes of Twist Channel Angular Pressing TCAP (with helical component), cyclic compression to total strain epsilon = 5 using MAXStrain Gleeble equipment, both performed at temperature interval 160-200 A degrees C and, as third SPD method, KOBO type extrusion at RT. The TCAP pass resulted in grain refinement of alpha phase from 30 mu m down to about 2 mu m and that of beta phase from 12 to 5 mu m. Maxstrain cycling 10 x up to epsilon = 5 led to much finer grain size of 300 nm. KOBO method performed at RT caused average grain size refinement of alpha and beta phases down to about 1 mu m. Hardness of alloy decreased slightly with increasing number of TCAP passes due to increase of small void density. It was higher after MAXStrain cycling and after KOBO extrusion. TEM studies after TCAP passes showed higher dislocation density in the beta region than in the alpha phase. Crystallographic relationship (001) alpha|| (110) beta indicated parallel positioning of slip planes of both phases. Electron diffraction technique confirmed increase of grain misorientation with number of TCAP passes. Stress/strain curves recorded at temperature 200 A degrees C showed superplastic forming after 1st and 3rd TCAP passes with better superplastic properties due to higher elongation with increasing number of passes. Values of strain rate sensitivity coefficient m were calculated at 0.29 after 3rd TCAP pass for strain rate range 10(-5) to 5 x 10(-3) s(-1). Deformation by MAXStrain cycling caused much more effective grain refinement with fine microtwins in alpha phase. Superplastic deformation was also observed in alloy deformed by KOBO method, however the value of m = 0.21 was obtained at lower temperature of deformation equal to 160 A degrees C and deformation rate in the range 10(-5) to 5 x 10(-3). Tensile samples deformed superplastically showed grain growth and void formation caused by grain boundary slip. Summarizing, all methods applied resulted in sufficient grain refinement to obtain the effect of superplastic deformation for alloys of two phase alpha + beta structure.Web of Science2451089107

Microstructural, corrosion and mechanical properties of a WE43 alloy

A hexagonal close-packed-structure WE43 alloy was extruded without any preheating of the initial billet using extrusion with an oscillating die to improve the corrosion and mechanical properties. The WE43 alloy was extruded at high ratios of R 1 5:1, R 2 7:1 and R 3 10:1. Electron back-scatter diffraction and transmission electron microscopy were used to determine the microstructural properties of the alloys. The influence of the extrusion method and the extrusion ratios on the corrosion and mechanical properties were investigated. Electrochemical tests were performed, and the corrosion damage was inspected. Tensile tests were made using micro specimens. When compared to conventional extrusion, the microstructural changes obtained with the KoBo method at R 5:1 increased the corrosion resistance, which was not only due to the grain refinement, but also due to the intensity of the texture. A decline in the corrosion resistance of the alloys deformed at higher extrusion ratios was observed. This was a result of the massive plastic strain imposed by the KoBo die. The room-temperature mechanical properties of the KoBo-extruded alloys were improved. However, at higher temperatures the mechanical properties decreased due to the solutioning of tiny triple precipitates