Key Engineering Materials Vol. 682

Abstract: The results of the microstructure and hardness investigations of the Cu-0.8Cr alloy after application of severe plastic deformation (SPD) implemented by rolling with the cyclic movement of rolls (RCMR) are presented in this paper. Performed substructure investigations showed that using the RCMR method can refine the microstructure of Cu-0.8Cr alloy to the ultrafine scale. The structure of the Cu-0.8Cr alloy was analyzed using light microscope (LM) and scanning transmission electron microscope (STEM). The quantitative studies of the substructure was performed with "MET-ILO" software, on the basis of images acquired on STEM microscope.

Abstract: In the paper, the influence of homogenization parameters on the microstructure and properties of the 5019 alloy DC-cast billets was analysed. At the first stage, the microstructure of the alloy in as-cast state was investigated using SEM/EDS technique. Additionally, a DSC test and hardness measurements were performed. In the as-cast material, the presence of the dendritic microstructure with a pronounced microsegregation of magnesium in the dendrites cross-section was found. Subsequently, the specimens were subjected to laboratory homogenization experiments, with different soaking conditions and water quenching. The microstructural effects of the investigated variants of homogenization were evaluated using the same techniques as in the case of the as-cast alloy. It was found that after homogenization, with soaking at the temperature of 530 °C for 6 hours, the microsegregation is eliminated and the concentration of magnesium in the grains centres is over two times greater than in the dendrites cores before annealing. The solidus temperature rises by about 12 °C in comparison to the as-cast state. Neither extending the soaking time nor rising the temperature contributes to a further increase of the solidus temperature, or the magnesium concentration in the grains interiors. However, the tendency of dispersoids to grow and the change of Fe-bearing constituents chemical composition were observed after the high temperature, or prolonged annealing variants.

Abstract: The relationship between friction stir processing (FSP) parameters and longitudinal residual stress profiles in modified cast aluminium alloy AlSi9Mg is presented. The influence of tool geometry, rotational speed and the number of processing passes were analysed. To experimentally measure residual stress, the trepanation method was adopted. The results indicated that an increase in the rotational speed caused an increase in the residual stress. Also, the Triflute tool promoted a higher level of residual stress than a conventional FSP tool. The region around the FSP bead was characterised by tensile residual stress fields that were balanced by compressive stresses in the parent material. A higher residual stress is observed on the advancing side than on the retreating side. An increase in the number of processing passes increased the level of residual stress in the modified material.

Abstract: Investigation results concerning changes occurring in the microstructure of the near β titanium alloy, grade: Ti13Nb13Zr, when the ageing temperature was changed within the range 350÷650°C, are presented in the paper. These changes were assessed on samples previously quenched in water from the selected soaking temperature in the single-phase β range (800°C). Microstructures were investigated by means of the optical microscopy and scanning electron microscopy (SEM). Phases occurring in the alloy at various ageing temperatures were identified with using the XRD analysis. Microstructure investigations were supplemented by hardness measurements by means of the Vickers apparatus, type HP0 250. In addition, for the selected ageing temperatures, the Charpy impact tests were performed on the Ti13Nb13Zr alloy samples. These tests were carried out on the Charpy tester of a potential energy of 150 J. The results of Charpy impact tests were supported by the fractographic documentation of samples fractures. The fractographic investigations were performed by means of the scanning electron microscope NovaNanoSEM 450.The obtained results constitute the valuable supplementation of the data bases concerning microstructures and mechanical properties of near β titanium alloys.

Abstract: Dissimilar aluminum alloy plates of 2017A-T451 and 7075-T651 with 6 mm thickness were friction stir butt welded. Numerous trials were conducted to determine the conditions that produce the highest weld quality. These parameters were found to be a welding speed of 112 mm/min, a rotation speed of 355 rev/min and a vertical force of 32,8 kN. The weldability and blending of the two materials were evaluated by using macro- and microstructural analysis as well as EDS mapping to show the distribution of main alloying elements within the weld. The effect of material locations, either on the advancing or retreating sides, on the microstructure and mechanical properties was also investigated. Hardness profiles differ substantially for different weld configurations. Regardless of the position of a particular alloy, the weld microstructure was composed of alternating layers of both materials. However, the layers of the 7075 alloy always exhibited smaller grain size and a larger number of secondary phase particles.

Abstract: Twin roll casting (TRC) technology is becoming increasingly popular because of the opportunity to receive aluminum strips which may serve as input for direct cold rolling processes. Furthermore, these strips have a favourable combination of mechanical and electric properties as well as dimensional tolerances. TRC line strips show segregation of alloying elements and structure providing a combination of casting structure and wrought alloy. As part of this study, the structure of the strips from the TRC line has been analyzed as well as the segregation of the alloying elements.

Abstract: The paper raises the issue of antimicrobial copper and its alloys constituting a promising solution for the constantly increasing problem of dangerous hospital-acquired infections. The major aim of the presented work is a precise analysis of antimicrobial copper alloys approved by The Environmental Protection Agency (EPA) in accordance with the Unified Numbering System, taking into account their European and international equivalent symbols as well – CEN and ISO, respectively. The analysis focuses mostly on the copper alloy types which the EPA list is composed of, their prices as well as materials and technological properties.

Abstract: The WE43 is a Mg-Y-Nd alloy that presents good mechanical properties and an high creep resistance. For these reasons currently is widely used in the aerospace and automotive industries. The setting of the right thermal heat treatment parameters plays a crucial role in determine the microstructure and consequently the mechanical properties of the alloy. With this in mind, the main goal of this work has been that to identify the optimal parameters to achieve a high impact resistance and at the same time, the most suitable choice, to reach also an important cost-saving solution, which is extremely important especially from the industrial point of view.

Abstract: Modern power industry expects new, dedicated aluminum based alloys with non-standard properties, including increased resistance to temperature. Materials exhibiting higher thermal resistance allow to increase operating temperature of electrical conductors, which results in the increase of their current carrying capacity. Commonly known and used in such applications are alloys from the AlZr group. Despite their advantages scientists from around the world are searching for new alternatives. In this paper authors present research results on Al-Mo and Al-Ag alloys with particular interest to the analysis of the molybdenum addition to the aluminum in the amount of 0.05, 0.1, 0.2% and silver addition in the amount of 0.05, 0.1, 0.15% by mass on the mechanical and electrical properties of obtained alloys. Tests were also carried out for reference material which is high-purity aluminum and the AlZr alloy, both in the as cast state temper. Results showed a significant change of temperature coefficient of resistance in Al-Ag alloys compared to Al, which leads to possible increase of the Joule’a heat without the raise of conductors temperature limit. On the other hand, above-average heat resistance of alloys from the Al-Mo group of materials was achieved during the trials. On that basis authors state that Al-Ag alloys may be used for the production of ACSS conductors and Al-Mo alloys for TACSR or TACIR type of conductors.This study was performed under a project financed by NCBiR within the INNOTECH II program.