The solidification characteristics and the hot tearing susceptibility were investigated on two Ni-based superalloys for turbocharger turbine wheel, K418 and K419. The segregation behaviors of the alloying elements and...The solidification characteristics and the hot tearing susceptibility were investigated on two Ni-based superalloys for turbocharger turbine wheel, K418 and K419. The segregation behaviors of the alloying elements and the precipitation phases were also studied. The results show that the solidification behavior of K419 alloy is complicated when compared with K418 due to the interdendritic segregation of many kinds of strong interdendritic partitioning elements in the remaining liquid at the final stage of solidification. The segregation of multiple elements in interdendritic liquid results in an extremely low solidus in K419. A long residual liquid stage is found during the solidification of K419, giving rise to reduced cohesion strength of dendrites and increased sensitivity to hot tearing. A hot tearing susceptibility coefficient（HTS） criterion is proposed based on a hot tearing sensitive model. The HTS value of K419 alloy is larger than that of K418 alloy.展开更多
Effects of Zn content (0, 0.5%, 1.5% and 4.5%) on the hot tearing characteristics of Mg?2%Y alloy were studied in aconstrained rod casting (CRC) apparatus attached with a load cell and data acquisition system. The exp...Effects of Zn content (0, 0.5%, 1.5% and 4.5%) on the hot tearing characteristics of Mg?2%Y alloy were studied in aconstrained rod casting (CRC) apparatus attached with a load cell and data acquisition system. The experimental results indicate thatthe hot tearing susceptibility (HTS) is affected by the content of Zn. The Zn-free base alloy shows the lowest HTS. The HTS ofMg?xZn?2Y alloys increases with increasing Zn content, reaches the maximum at 1.5% Zn, and then decreases with further Znaddition. The high HTS observed in the alloy with 1.5% Zn is attributed to its high force release rate and large force drop duringsolidification. The hot cracks of casting are initiated and propagate along the dendritic or grain boundaries. The predictions of HTS ofMg?xZn?2Y alloys using ProCAST software are in good agreement with the results obtained by experimental measurements.展开更多
Background:Currently,there are no drugs that have been proven to be effective against severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).Because of its broad antiviral activity,interferon(IFN)should be evalua...Background:Currently,there are no drugs that have been proven to be effective against severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).Because of its broad antiviral activity,interferon(IFN)should be evaluated as a potential therapeutic agent for treatment of coronavirus disease 2019(COVID-19),especially while COVID-19-specific therapies are still under development.Methods:Confirmed COVID-19 patients hospitalized in the First Affiliated Hospital,School of Medicine,Zhejiang University in Hangzhou,China,from January 19 to February 19,2020 were enrolled in a retrospective study.The patients were separated into an IFN group and a control group according to whether they received initial IFN-α2 b inhalation treatment after admission.Propensity-score matching was used to balance the confounding factors.Results:A total of 104 confirmed COVID-19 patients,68 in the IFN group and 36 in the control group,were enrolled.Less hypertension(27.9%vs.55.6%,P=0.006),dyspnea(8.8%vs.25.0%,P=0.025),or diarrhea(4.4%vs.19.4%,P=0.030)was observed in the IFN group.Lower levels of albumin and C-reactive protein and higher level of sodium were observed in the IFN group.Glucocorticoid dosage was lower in the IFN group(median,40 vs.80 mg/d,P=0.025).Compared to the control group,fewer patients in the IFN group were ventilated(13.2%vs.33.3%,P=0.015)and admitted to intensive care unit(ICU)(16.2%vs.44.4%,P=0.002).There were also fewer critical patients in the IFN group(7.4%vs.25.0%,P=0.017)upon admission.Although complications during admission process were comparable between groups,the discharge rate(85.3%vs.66.7%,P=0.027)was higher and the hospitalization time(16 vs.21 d,P=0.015)was shorter in the IFN group.When other confounding factors were not considered,virus shedding time(10 vs.13 d,P=0.014)was also shorter in the IFN group.However,when the influence of other factors was eliminated using propensity score matching,virus shedding time was not significantly shorter than that of the control group(12 vs.15 d,P=0.206).Conclusions:IFN-α2 b spray inhalation did not shorten virus shedding time of SARS-CoV-2 in hospitalized patients.展开更多
基金Project(2010CB631200)supported by the National Basic Research Program of China
文摘The solidification characteristics and the hot tearing susceptibility were investigated on two Ni-based superalloys for turbocharger turbine wheel, K418 and K419. The segregation behaviors of the alloying elements and the precipitation phases were also studied. The results show that the solidification behavior of K419 alloy is complicated when compared with K418 due to the interdendritic segregation of many kinds of strong interdendritic partitioning elements in the remaining liquid at the final stage of solidification. The segregation of multiple elements in interdendritic liquid results in an extremely low solidus in K419. A long residual liquid stage is found during the solidification of K419, giving rise to reduced cohesion strength of dendrites and increased sensitivity to hot tearing. A hot tearing susceptibility coefficient（HTS） criterion is proposed based on a hot tearing sensitive model. The HTS value of K419 alloy is larger than that of K418 alloy.
基金Financial supports from China Scholarship Council and Helmholtz Association of German Research Centers scholarship(No.2010821213) for Wang’s Ph D study in Helmholtz-Zentrum Geesthacht(HZG) are gratefully acknowledged
文摘Effects of Zn content (0, 0.5%, 1.5% and 4.5%) on the hot tearing characteristics of Mg?2%Y alloy were studied in aconstrained rod casting (CRC) apparatus attached with a load cell and data acquisition system. The experimental results indicate thatthe hot tearing susceptibility (HTS) is affected by the content of Zn. The Zn-free base alloy shows the lowest HTS. The HTS ofMg?xZn?2Y alloys increases with increasing Zn content, reaches the maximum at 1.5% Zn, and then decreases with further Znaddition. The high HTS observed in the alloy with 1.5% Zn is attributed to its high force release rate and large force drop duringsolidification. The hot cracks of casting are initiated and propagate along the dendritic or grain boundaries. The predictions of HTS ofMg?xZn?2Y alloys using ProCAST software are in good agreement with the results obtained by experimental measurements.
基金Project supported by the National Natural Science Foundation of China(No.81700549)the National Major Science and Technology Research Projects for the Control and Prevention of Major Infectious Diseases in China(No.2017ZX10202202)the Medical and Health Research Program of Zhejiang Province(No.2015KYB144),China。
文摘Background:Currently,there are no drugs that have been proven to be effective against severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).Because of its broad antiviral activity,interferon(IFN)should be evaluated as a potential therapeutic agent for treatment of coronavirus disease 2019(COVID-19),especially while COVID-19-specific therapies are still under development.Methods:Confirmed COVID-19 patients hospitalized in the First Affiliated Hospital,School of Medicine,Zhejiang University in Hangzhou,China,from January 19 to February 19,2020 were enrolled in a retrospective study.The patients were separated into an IFN group and a control group according to whether they received initial IFN-α2 b inhalation treatment after admission.Propensity-score matching was used to balance the confounding factors.Results:A total of 104 confirmed COVID-19 patients,68 in the IFN group and 36 in the control group,were enrolled.Less hypertension(27.9%vs.55.6%,P=0.006),dyspnea(8.8%vs.25.0%,P=0.025),or diarrhea(4.4%vs.19.4%,P=0.030)was observed in the IFN group.Lower levels of albumin and C-reactive protein and higher level of sodium were observed in the IFN group.Glucocorticoid dosage was lower in the IFN group(median,40 vs.80 mg/d,P=0.025).Compared to the control group,fewer patients in the IFN group were ventilated(13.2%vs.33.3%,P=0.015)and admitted to intensive care unit(ICU)(16.2%vs.44.4%,P=0.002).There were also fewer critical patients in the IFN group(7.4%vs.25.0%,P=0.017)upon admission.Although complications during admission process were comparable between groups,the discharge rate(85.3%vs.66.7%,P=0.027)was higher and the hospitalization time(16 vs.21 d,P=0.015)was shorter in the IFN group.When other confounding factors were not considered,virus shedding time(10 vs.13 d,P=0.014)was also shorter in the IFN group.However,when the influence of other factors was eliminated using propensity score matching,virus shedding time was not significantly shorter than that of the control group(12 vs.15 d,P=0.206).Conclusions:IFN-α2 b spray inhalation did not shorten virus shedding time of SARS-CoV-2 in hospitalized patients.
