A wear-resistant steel was hot rolled at the same finish temperature, and subsequently treated with conventional reheat quenching and tempering process （RQ＆T） and direct quenching and tempering process （DQ＆T）, r...A wear-resistant steel was hot rolled at the same finish temperature, and subsequently treated with conventional reheat quenching and tempering process （RQ＆T） and direct quenching and tempering process （DQ＆T）, respectively. The effect of direct quenching on the microstructure and mechanical properties was investigated in detail by using optical microscope, transmission electron microscope and scanning electron microscope equipped with electron backscattered diffraction. The results showed that the microstructures of both the RQ and DQ specimens were complex constituents of lath martensite and lower bainite. Compared with the RQ specimen, the lower bainite content in DQ specimen was much higher. Furthermore, the bainite in the DQ specimen extended into and segmented the prior austenite grains, which can decrease martensite packet size. The proportion of high-angle boundary in the DQ specimen was higher than that in the RQ specimen, which may improve the impact toughness. The carbides in DQ＆_T specimen were much finer and distributed even dispersively because direct quenching can retain substantive defects which may provide more nucleation sites for carbide precipitation in the tempering process. Besides, the mechanical properties of DQ and DQ＆T specimens were superior than those subjected to RQ and RQ＆T processes, respectively.展开更多
Thermomechanical process and tempering heat treatment were employed to produce the experimental steel plates. The effect of boron addition on the microstructure and mechanical properties of low carbon bainitic steels ...Thermomechanical process and tempering heat treatment were employed to produce the experimental steel plates. The effect of boron addition on the microstructure and mechanical properties of low carbon bainitic steels was studied in this paper. Microstructure observation and crystallographic features were conducted by using optical microscopy, SEM, TEM and electron back scattering diffraction （EBSD） analysis. The results showed that under the same rolling processes and heat treatment conditions, a substantial increase in strength is obtained by addition of boron into steel, but accompanied by an obvious drop in toughness. New martensite phase forms along the grain boundaries on tempering at 650℃ mainly due to boron segregation, which can further deteriorate impact toughness of the boron bearing steel. The EBSD analysis showed that high angle grain boundary, is not responsible for the deteriorated toughness of the boron bearing steel because it has relatively higher percentage of high angle grain boundary than the boron free steel. The low toughness of the boron bearing steel is mainly attributed to the coarse boride precipitated particles according to the results of fractograph observation.展开更多
Introduction: Anti-Müllerian hormone (AMH) is shown to be a possible indicator of ovarian function. Severe systemic lupus erythematosus (SLE) patients exposed to high-dose cyclophosphamide (CTX) have a much highe...Introduction: Anti-Müllerian hormone (AMH) is shown to be a possible indicator of ovarian function. Severe systemic lupus erythematosus (SLE) patients exposed to high-dose cyclophosphamide (CTX) have a much higher risk of developing infertility and premature ovarian failure. Therefore, we performed a prospective case-control study to evaluate the impact of SLE on women’s ovarian reserve using AMH before CTX therapy. Methods: SLE patients before receiving CTX therapy were enrolled in our hospital. Age-matched healthy women were served as controls. Serum AMH level was measured using an enzyme-linked immunosorbent assay. Basal hormone levels were measured including follicle-stimulating hormone, luteinizing hormone, and estradiol on the third day of their menstrual periods. All participants underwent transvaginal ultrasonographic examination for the determination of total antral follicle count on the third day. Results: AMH value in SLE patients was significantly lower compared to healthy control with normal ovarian reserve. No significant difference in AMH levels was found between SLE and healthy control with low ovarian reserve. Conclusions: SLE patients not receiving CTX therapy even with normal menstruation, still had an impaired ovarian reserve. Therefore, early monitoring of AMH levels could better reflect the ovarian function and reproductive outcomes of SLE patients and relative protective strategy needed to reserve fertility.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51074052 and 51004035)
文摘A wear-resistant steel was hot rolled at the same finish temperature, and subsequently treated with conventional reheat quenching and tempering process （RQ＆T） and direct quenching and tempering process （DQ＆T）, respectively. The effect of direct quenching on the microstructure and mechanical properties was investigated in detail by using optical microscope, transmission electron microscope and scanning electron microscope equipped with electron backscattered diffraction. The results showed that the microstructures of both the RQ and DQ specimens were complex constituents of lath martensite and lower bainite. Compared with the RQ specimen, the lower bainite content in DQ specimen was much higher. Furthermore, the bainite in the DQ specimen extended into and segmented the prior austenite grains, which can decrease martensite packet size. The proportion of high-angle boundary in the DQ specimen was higher than that in the RQ specimen, which may improve the impact toughness. The carbides in DQ＆_T specimen were much finer and distributed even dispersively because direct quenching can retain substantive defects which may provide more nucleation sites for carbide precipitation in the tempering process. Besides, the mechanical properties of DQ and DQ＆T specimens were superior than those subjected to RQ and RQ＆T processes, respectively.
基金financially supported by the National Natural Science Foundation of China (No.51074052)the Fundamental Research Funds of the Central Universities (No.N100607001)
文摘Thermomechanical process and tempering heat treatment were employed to produce the experimental steel plates. The effect of boron addition on the microstructure and mechanical properties of low carbon bainitic steels was studied in this paper. Microstructure observation and crystallographic features were conducted by using optical microscopy, SEM, TEM and electron back scattering diffraction （EBSD） analysis. The results showed that under the same rolling processes and heat treatment conditions, a substantial increase in strength is obtained by addition of boron into steel, but accompanied by an obvious drop in toughness. New martensite phase forms along the grain boundaries on tempering at 650℃ mainly due to boron segregation, which can further deteriorate impact toughness of the boron bearing steel. The EBSD analysis showed that high angle grain boundary, is not responsible for the deteriorated toughness of the boron bearing steel because it has relatively higher percentage of high angle grain boundary than the boron free steel. The low toughness of the boron bearing steel is mainly attributed to the coarse boride precipitated particles according to the results of fractograph observation.
文摘Introduction: Anti-Müllerian hormone (AMH) is shown to be a possible indicator of ovarian function. Severe systemic lupus erythematosus (SLE) patients exposed to high-dose cyclophosphamide (CTX) have a much higher risk of developing infertility and premature ovarian failure. Therefore, we performed a prospective case-control study to evaluate the impact of SLE on women’s ovarian reserve using AMH before CTX therapy. Methods: SLE patients before receiving CTX therapy were enrolled in our hospital. Age-matched healthy women were served as controls. Serum AMH level was measured using an enzyme-linked immunosorbent assay. Basal hormone levels were measured including follicle-stimulating hormone, luteinizing hormone, and estradiol on the third day of their menstrual periods. All participants underwent transvaginal ultrasonographic examination for the determination of total antral follicle count on the third day. Results: AMH value in SLE patients was significantly lower compared to healthy control with normal ovarian reserve. No significant difference in AMH levels was found between SLE and healthy control with low ovarian reserve. Conclusions: SLE patients not receiving CTX therapy even with normal menstruation, still had an impaired ovarian reserve. Therefore, early monitoring of AMH levels could better reflect the ovarian function and reproductive outcomes of SLE patients and relative protective strategy needed to reserve fertility.
