Nisub.47Tisub.44Nbsub.9 alloys were successfully fabricated by laser powder bed fusion (LPBF) technique with different laser powers. The phase transformation behavior, tensile properties and shape ...memory response before and after heat treating were also investigated. The Nisub.47Tisub.44Nbsub.9 LPBF alloys have good shaping properties, though a few defects were discovered. Phase transformation peaks did not appear in the as-built samples, but were observed in the heat-treated samples. The phase transformation temperatures of the heat-treated samples increase with the increase in laser power. The tension test at room temperature indicates that the LPBF samples exhibit poor tensile ductility, which may be related to the existence of pores and Tisub.2Ni or Tisub.4Nisub.2Osub.x phase during the LPBF process. However, the LPBF samples after heat treating still possess good shape memory effect (with recovery strain about 7.82-8%) and relatively high reverse transformation temperature (about 36-52.6 °C) when deformed to 8%.
This work aims to clarify the influence of texture type and intensity on the shape memory effect (SME) in NiTiNb shape memory alloy (SMA) pipe joints, especially revealing the causes for the ...anisotropy of SME via texture changes. Three NiTiNb rods with different intensities of the {111} texture were fabricated, and their microstructures, crystalline orientation distribution functions and inverse pole figures were obtained by X-ray diffraction and electron backscatter diffraction measurements. Simultaneously, the SME was characterized by inner-diameter recoverability of the corresponding pipe joints. For a given intensity of the {111} texture, the SME of the NiTiNb pipe joints strongly depended on the expansion direction due to {111} orientation-induced anisotropy of SME. In addition, both the SME and anisotropy of NiTiNb pipe joints increased with the increased intensity of the {111} texture. Therefore, a suitable expansion direction and strong texture intensity should be considered for high SME in NiTiNb pipe joints.
This work aims to clarify the influence of texture type and intensity on the shape memory effect (SME) in NiTiNb shape memory alloy (SMA) pipe joints, especially revealing the causes for the ...anisotropy of SME via texture changes. Three NiTiNb rods with different intensities of the {111} texture were fabricated, and their microstructures, crystalline orientation distribution functions and inverse pole figures were obtained by X-ray diffraction and electron backscatter diffraction measurements. Simultaneously, the SME was characterized by inner-diameter recoverability of the corresponding pipe joints. For a given intensity of the {111} texture, the SME of the NiTiNb pipe joints strongly depended on the expansion direction due to {111} orientation-induced anisotropy of SME. In addition, both the SME and anisotropy of NiTiNb pipe joints increased with the increased intensity of the {111} texture. Therefore, a suitable expansion direction and strong texture intensity should be considered for high SME in NiTiNb pipe joints.
HR-2 is a single-phase austenitic stainless steel with excellent hydrogen embrittlement resistance and a wide range of applications in hydrogen storage pressure vessels. During the powder preparation ...and additive manufacturing process, burning nitrogen deteriorates its hydrogen embrittlement resistance and mechanical properties. In this paper, HR-2 stainless steel powder was prepared by vacuum induction melting atomization (VIGA), and the HR-2 powder with acceptable nitrogen content was obtained in a nitrogen atmosphere. The effects of process parameters in selective laser melting, including laser energy density on the part density, microstructure, and mechanical properties of the formed specimens, were investigated. The results show the density of the formed samples first increase and then decrease as the energy density increases. With the optimization of process parameters, the density of the parts fabricated by SLM formed HR-2 with low nitrogen can reach more than 99.5%, the tensile strength can reach 735 ± 5 MPa, the yield strength can reach 415 ± 10 MPa, the percentage elongation of 43 ± 5%, and percentage reduction of 44 ± 5%, while the tensile strength of HR-2 with high nitrogen can reach 720 ± 10 MPa, the yield strength can reach 603.5 ± 10 MPa, the percentage elongation of 45 ± 5%, and percentage reduction of 60 ± 5%, which are comparable with the base material of forged HR-2.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Based on extended Derjaguin-Landau-Verwey-Overbeek theory, a heterocoagulation model is proposed for magnetorheological (MR) fluids containing like-charged nanosized and micron particles without a ...magnetic field. This model considers three major interactions, namely van der Waals attraction, electrical double layer (EDL) interaction, and steric repulsion. The EDL interaction has been identified as the most important factor. The surface potential ratio β (ψ
2
/ψ
1
) between two dissimilar particles with like charge plays an important role in controlling the change of EDL interaction. At higher β ratios, the EDL interaction becomes attractive when the surface separation falls within a certain range. Two groups of MR fluid samples have been used in experimental studies based on electroacoustic measurements. In the first group, the ratio and the sum of the zeta potentials between carbonyl iron particles and ceria were 4 and −734.57 mV, respectively. In the second group, these parameters were 1.38 and −108.17 mV, respectively. The experimental results suggested that the second group did not undergo heterocoagulation, whereas the first group showed extensive heterocoagulation. The difference in surface potentials between particles of two different phases has been found to be critical for determining the state of dispersion or heterocoagulation in concentrated MR fluid systems.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
In recent years, the study of incidental vocabulary acquisition has received worldwide attention from scholars at home and abroad. Based on the relevant literature and some relevant empirical ...studies, this paper mainly explores the influence of reading purposes on the incidental acquisition of second language vocabulary in natural reading. It also put forward some constructive suggestions on how to use these factors to guide students' vocabulary learning.
The influences of strain amplitude (10
−5–10
−4) and temperature (25
°C–500
°C) on the internal friction of a cold-drawn and solution treated Fe-19Mn alloy were investigated. The internal friction ...was measured using reversal torsion pendulum and multifunction internal friction equipment. The microstructure was observed using scanning electron microscopy. The phase transformation temperatures were determined using differential scanning calorimetry. The results indicated that the internal friction of the solution treated alloy was related to strain amplitude, which could be explained using the movement of Shockley partial dislocations (bowing out and breaking away). But the internal friction of the cold-drawn alloy was independent of strain amplitude because of high density dislocations formed by cold forming. Moreover, when the temperature was changed between 25
°C and 500
°C, the internal friction of the cold-drawn alloy increased slowly from 25
°C to 375
°C, and then increased quickly from 375
°C to 500
°C. However, for the solution treated alloy, there was an internal friction peak at about 210
°C in the heating process (from 25
°C to 500
°C), and there was another internal friction peak at about 150
°C in the cooling process. These peaks could be explained using the heat-assisted movement of dislocations.
►Internal friction of solution treated Fe-19Mn alloy is related to strain amplitude. ►Internal friction of cold-drawn Fe-19Mn alloy is independent of strain amplitude. ►IF of cold-drawn alloy increases from RT to 500
°C. ►There is an IF peak of solution treated alloy in heating and cooling process separately. ►The results can be explained using the movement of dislocations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract
Background
Various types of pulmonary diseases are associated with iron deficiency. However, information on iron status in coronavirus disease 2019 (COVID-19) is scarce.
Methods
This study ...included 50 hospitalized patients with confirmed COVID-19. The role of serum iron in predicting severity and mortality of COVID-19 was evaluated.
Results
The most common symptoms of COVID-19 patients in this study were cough (82%), fever (64%), and chest distress (42%). Of the 50 patients, 45 (90%) patients had abnormally low serum iron levels (<7.8 μmol/L). The severity of COVID-19 was negatively correlated with serum iron levels before and after treatment and was positively correlated with C-reactive protein, serum amyloid A, D-dimer, lactate dehydrogenase, urea nitrogen, and myoglobin levels. Decreased serum iron level could predict the transition of COVID-19 from mild to severe and critical illness. Seven (53.8%) patients with a lower serum iron level after treatment in the critical group had died. There was a significant difference in posttreatment serum iron levels between COVID-19 survivors and nonsurvivors.
Conclusions
Serum iron deficiency was detected in the patients with COVID-19. The severity and mortality of the disease was closely correlated with serum iron levels. Low serum iron concentration was an independent risk factor for death in COVID-19 patients.
Serum iron deficiency occurs in COVID-19. Critically ill patients with COVID-19 who died during hospitalization had significantly lower serum iron levels compared with those survivors. Decreased serum iron level can predict the transition of mild to critical COVID-19.
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