The spheroidization behavior of the dendritic b.c.c, phase dispersed in a bulk metallic glass (BMG) matrix was investigated through applying semi-solid isothermal processing and a subsequent rapid quenching procedur...The spheroidization behavior of the dendritic b.c.c, phase dispersed in a bulk metallic glass (BMG) matrix was investigated through applying semi-solid isothermal processing and a subsequent rapid quenching procedure to a Zr-basedβ-phase composite. The Zr-based composite with the composition of Z%62Ti138NbsoCuegNi5.6Be125 was prefabricated by a water-cooled copper mold-casting method and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the composite consists of a glassy matrix and uniformly distributed fine dendrites of theβ-Zr solid solution with the body-centered-cubic (b.c.c.) structure. Based on the differential scanning calorimeter (DSC) examination results, and in view of the b.c.c.β-Zr to h.c.p, α-Zr phase transition temperature, a semi-solid holding temperature of 900 ℃ was determined. After reheating the prefabricated composite to the semi-solid temperature, followed by an isothermal holding process at this temperature for 5 min, and then quenching the semi-solid mixture into iced-water; the two-phase microstructure composed of a BMG matrix and uniformly dispersed spherical b.c.c.β-Zr particles with a high degree of sphericity was achieved. The present spheroidization transition is a thermodynamically autonomic behavior, and essentially a diffusion process controlled by kinetic factors; and the formation of the BMG matrix should be attributed to the rapid quenching of the semi-solid mixture as well as the large glass-forming ability of the remaining melt in the semi-solid mixture.展开更多
The effect of subcritical annealing temperature on microstructure and mechanical properties of SCM435 steel was investigated through changing the heating and soaking temperature as 660 °C, 680 °C, 700 °...The effect of subcritical annealing temperature on microstructure and mechanical properties of SCM435 steel was investigated through changing the heating and soaking temperature as 660 °C, 680 °C, 700 °C, 720 °C and 745 °C. The microstructure and mechanical properties of intercritically annealed specimens were analyzed. With increasing the subcritical annealing temperature from 660 °C to 720 °C, the spheroidization ratio gradually increased, and the mechanical properties, formability and Vickers hardness were improved. According to the comprehensive comparison of mechanical properties and formability, the subcritical process at soaking temperature of 680-720 °C could achieve similar annealing effect as that of intercritical process. Therefore, the subcritical annealing temperature could be set as 700 °C in practice, with the Ac1 temperature fluctuation within ±20 °C, and the applicability and stability of subcritical annealing were guaranteed in industrial application. The plant results of the cold heading showed that the subcritical annealing could replace original intercritical annealing successfully with significantly saving time and energy.展开更多
The spheroidizing mechanism of W-phase in the Mg–Zn–Y–Mn–(B) alloys during solid-solution treatment was investigated by using kinetic methodologies. The microstructure and mechanical properties of heat-treated ...The spheroidizing mechanism of W-phase in the Mg–Zn–Y–Mn–(B) alloys during solid-solution treatment was investigated by using kinetic methodologies. The microstructure and mechanical properties of heat-treated Mg_(94)Zn_(2.5)-Y_(2.5)Mn_1 alloy containing 0.003 wt% B were compared with heat-treated Mg_(94)Zn_(2.5)-Y_(2.5)Mn_1 alloy. The heat-treated Mg_(94)Zn_(2.5)-Y_(2.5)Mn_1 alloy with 0.003 wt% B contained fine and uniform W-phase particles, which exhibited optimal mechanical performance. The ultimate tensile strength, yield strength and elongation were 287.7, 125.5 MPa and 21.1%,respectively.展开更多
基金supported by the Natural Science Research Projects of The Education Department of Henan Province,China(Grant No.2008A430010)the R&D start-up projects of high-level talents of North China University of Water Resources and Electric Power(Grant No.200709)
文摘The spheroidization behavior of the dendritic b.c.c, phase dispersed in a bulk metallic glass (BMG) matrix was investigated through applying semi-solid isothermal processing and a subsequent rapid quenching procedure to a Zr-basedβ-phase composite. The Zr-based composite with the composition of Z%62Ti138NbsoCuegNi5.6Be125 was prefabricated by a water-cooled copper mold-casting method and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the composite consists of a glassy matrix and uniformly distributed fine dendrites of theβ-Zr solid solution with the body-centered-cubic (b.c.c.) structure. Based on the differential scanning calorimeter (DSC) examination results, and in view of the b.c.c.β-Zr to h.c.p, α-Zr phase transition temperature, a semi-solid holding temperature of 900 ℃ was determined. After reheating the prefabricated composite to the semi-solid temperature, followed by an isothermal holding process at this temperature for 5 min, and then quenching the semi-solid mixture into iced-water; the two-phase microstructure composed of a BMG matrix and uniformly dispersed spherical b.c.c.β-Zr particles with a high degree of sphericity was achieved. The present spheroidization transition is a thermodynamically autonomic behavior, and essentially a diffusion process controlled by kinetic factors; and the formation of the BMG matrix should be attributed to the rapid quenching of the semi-solid mixture as well as the large glass-forming ability of the remaining melt in the semi-solid mixture.
基金Item Sponsored by National Natural Science Foundation of China(51474058)Fundamental Research Funds for the Central Universities of China(N130402017)
文摘The effect of subcritical annealing temperature on microstructure and mechanical properties of SCM435 steel was investigated through changing the heating and soaking temperature as 660 °C, 680 °C, 700 °C, 720 °C and 745 °C. The microstructure and mechanical properties of intercritically annealed specimens were analyzed. With increasing the subcritical annealing temperature from 660 °C to 720 °C, the spheroidization ratio gradually increased, and the mechanical properties, formability and Vickers hardness were improved. According to the comprehensive comparison of mechanical properties and formability, the subcritical process at soaking temperature of 680-720 °C could achieve similar annealing effect as that of intercritical process. Therefore, the subcritical annealing temperature could be set as 700 °C in practice, with the Ac1 temperature fluctuation within ±20 °C, and the applicability and stability of subcritical annealing were guaranteed in industrial application. The plant results of the cold heading showed that the subcritical annealing could replace original intercritical annealing successfully with significantly saving time and energy.
基金support from the National Natural Science Foundation of China(Nos.51474153 and 51574175)Ph.D.Programs Foundation of Ministry of Education of the People’s Republic of China(No.20111402110004)Natural Science Foundation of Shanxi Province(Nos.2009011028-3 and 2012011022-1)
文摘The spheroidizing mechanism of W-phase in the Mg–Zn–Y–Mn–(B) alloys during solid-solution treatment was investigated by using kinetic methodologies. The microstructure and mechanical properties of heat-treated Mg_(94)Zn_(2.5)-Y_(2.5)Mn_1 alloy containing 0.003 wt% B were compared with heat-treated Mg_(94)Zn_(2.5)-Y_(2.5)Mn_1 alloy. The heat-treated Mg_(94)Zn_(2.5)-Y_(2.5)Mn_1 alloy with 0.003 wt% B contained fine and uniform W-phase particles, which exhibited optimal mechanical performance. The ultimate tensile strength, yield strength and elongation were 287.7, 125.5 MPa and 21.1%,respectively.