Cu-Cr and Cu-Fe Alloys Processed by New Severe Plastic Deformation: Microstructure and Properties

In this chapter, two techniques have been proposed for grain refinement in Cu‐Cr and Cu‐Fe alloys in different heat treatment conditions. First method, known as rolling with cyclic movement of rolls (RCMR), is appropriate for the manufacturing of ultrafine grained sheets and plates. The second method is called compression with oscillatory torsion (COT). Structural investigations of alloys were carried out, in particular, using a cold field emission gun/scanning electron microscope (FEG/SEM) equipped with an electron backscattering diffraction (EBSD) detector and a scanning transmission electron microscope (STEM). Quantitative studies of the microstructure based on the STEM images were performed using the “MET‐ILO” software package. Mechanical properties were determined using an MST QTest/10 instrument equipped with digital image correlation (DIC). Based on the SEM and STEM observations, it has been shown that the alloys may exhibit a refinement of the ultra fine grained (UFG) structure in the 200–500 nm range with a mixture of low‐ and high‐angle boundaries. Although the microstructure was refined significantly, the heterogeneity of the microstructure after the application of a high total effective strain is observed. Moreover, the low‐angle boundaries formed at the early stages do not continuously transform into high‐angle boundaries

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

The severity of traumatic stress associated with COVID-19 pandemic, perception of support, sense of security, and sense of meaning in life among nurses : research protocol and preliminary results from Poland

The COVID-19 pandemic can not only affect physical health, but also mental health, resulting in sleep problems, depression, and traumatic stress. Our research investigates the level of posttraumatic stress, perceived social support, opinions on positive and negative consequences of the pandemic, sense of security and sense of meaning among nurses in the face of this new and not fully understood global epidemiological phenomenon. For this purpose, computer-assisted web interviews were conducted between May 1 and May 15, 2020. Participating nurses completed the following research tools: The Impact Event Scale-Revised (IES-R), The Multidimensional Scale of Perceived Social Support (MSPSS), The Changes in Outlook Questionnaire (CIOQ), The Safety Experience Questionnaire (SEQ) and The Meaning in Life Questionnaire (MLQ). Three hundred and twenty-five nurses of an average age of 39.18 ± 11.16 years and working throughout Poland joined the study. The average overall IES-R score in the study group was 1.78 ± 0.65. Among the dimensions of traumatic stress, the highest score was obtained in the “avoidance” dimension was 1.86 ± 0.73. Amongst participating nurses, the highest support rates were provided by significant others (22.58 ± 5.22). Higher average scores were noted among participants in the subscale measuring positive psychological changes (18.56 ± 4.04). The mean MLQ score was 5.33 ± 0.87. A slightly higher result was observed in the subscale “presence” (5.35 ± 1.14). The results of the research implemented during the period of severe psychological pressure associated with the COVID-19 pandemic provided information on symptoms of traumatic stress in the examined group of nurses. Their sense of security has been lowered and accompanied by an intensified reflection on issues concerning security. However, their current sense of meaning in life remains higher than the tendency to searching for it. The surveyed nurses received individual support mostly from significant others (i.e., other than family and friends). They see positive changes resulting from painful experiences related to the COVID-19 pandemic, which can be characterized by adaptation in the form of post-traumatic growth

High-temperature deformation properties of CuCr0.6 alloy

The submitted paper aimed to investigate the hot deformation behavior of CuCr0.6 alloy. Nil strength temperature of 1349 K and nil ductility temperature of 1313 K have been experimentally determined. Formability is monotonously increased with the decrease of forming temperature in the temperature range from 923 K to approx. 1273 K. The flow stress curves were obtained in the forming temperature interval of 923-1223 K and at a strain rate of 0.1-10 s(-1). After their analysis, the hot deformation activation energy of 340 kJ mol(-1) was calculated for peak stress and 393 kJ mol(-1) for steady state. This proves that the value of the activation energy depends upon a strain size.Web of Science57641440

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

PLASTICITY OF SELECTED METALLIC MATERIALS IN DYNAMIC DEFORMATION CONDITIONS

Characteristics of a modernized flywheel machine has been presented in the paper. The laboratory stand enables to perform dynamic tensile tests and impact bending with a linear velocity of the enforcing element in the range of 5÷40 m/s. A new data acquisition system, based on the tensometric sensors, allows for significant qualitative improvement of registered signals. Some preliminary dynamic forming tests were performed for the selected group of metallic materials. Subsequent microstructural examinations and identification of the fracture type enabled to describe a correlation between strain rate, strain and microstructure

Microstructural characterization of second phases in X10CrMoVNb9-1 and 12CrMoWCuVNb steels after long steam exposure time at 550 degrees C

Microstructural changes in high alloy (9–12% Cr) creep resistant martensitic X10CrMoVNb9–1 and 12CrMoW · CuVNb steels after 100 000 h of steam exposure at 550°C have been studied using scanning transmission electron microscopy. Precipitates were identified using electron diffraction patterns and energy dispersive X-ray spectroscopy analysis. After long time exposure, a significant coarsening of M23C6 carbides, and intensive precipitation of the coarse Laves phase were observed. Moreover, in the 12CrMoW · CuVNb steel, a low amount of the modified Z-phase particles was detected. The microstructures of the X10Cr · MoVNb9–1 and 12CrMoWCuVNb steels after 100 000 h of exposure differ in several aspects.Web of Science106780379