Creep aging forming(CAF) is a potential process used to manufacture large integral components of magnesium(Mg) alloys. The selected stress plays a crucial role in creep aging processes but the mechanism by which stres...Creep aging forming(CAF) is a potential process used to manufacture large integral components of magnesium(Mg) alloys. The selected stress plays a crucial role in creep aging processes but the mechanism by which stress loading method affects creep aging of Mg alloys is still unclear. In this paper, the microstructural evolution of precipitated phases and precipitation-free zones(PFZ) at grain boundaries with different stress loading modes(unstressed, unidirectional tensile stress, and cyclic stress) at 250 ℃ were investigated along with changes in mechanical properties. The results showed that the addition of stress during aging effectively promoted the precipitation of precipitated phases, while unaffecting grain size. Unidirectional tensile stress caused directional growth of β phase([1010]), as well as rotation of weave towards the basal plane texture, resulting in namely stress orientation effect. Solute atoms diffused in the direction of tensile stress while vacancies moved perpendicular to the direction of tensile stress, resulting in PFZ at grain boundaries(157.06 nm). By contrast, cyclic stresses led to the growth of β phase in three directions([1010], [1100] and [0110]). The solute atoms and vacancies were uniformly distributed in the Mg matrix instead of directional diffusion, effectively reducing the width of PFZ(112.39 nm) at the grain boundary. These features significantly improved the mechanical properties of alloy specimens after cyclic stress creep aging when compared to unidirectional stress creep aging, with yield strength(YS), ultimate tensile strength(UTS), and elongation(EL) enhanced from 171.6 MPa, 305.5 MPa, and 4.4%to 174.8 MPa, 326.3 MPa, and 6.9%, respectively.展开更多
基金National Natural Science Foundation of China(Nos.U2037601,51821001)Key Basic Research Project of the National Basic Strengthening Plan,China(No.2022-xxxx-ZD-093-xx)。
基金supported by Natural Science Foundation of Shanxi province (20210302123135,20210302123163)Science and Technology Major Project of Shanxi province (20191102008)+6 种基金Scientific and Technological Achievements Transformation Guidance Special Project of Shanxi province (202104021301022)The Ministry of Science and Higher Education of the Russian Federation for financial support under the Megagrant (No.075-15-2022-1133)the National Research Foundation (NRF) grant funded by the Ministry of Science and ICT (2015R1A2A1A01006795) of Korea through the Research Institute of Advanced MaterialsThe central government guided local science and technology development projects (YDZJSX2021A010)China Postdoctoral Science Foundation (2022M710541)the projects of International Cooperation in Shanxi (201803D421086)Research Project Supported by Shanxi Scholarship Council of China (2022- 038)。
文摘Creep aging forming(CAF) is a potential process used to manufacture large integral components of magnesium(Mg) alloys. The selected stress plays a crucial role in creep aging processes but the mechanism by which stress loading method affects creep aging of Mg alloys is still unclear. In this paper, the microstructural evolution of precipitated phases and precipitation-free zones(PFZ) at grain boundaries with different stress loading modes(unstressed, unidirectional tensile stress, and cyclic stress) at 250 ℃ were investigated along with changes in mechanical properties. The results showed that the addition of stress during aging effectively promoted the precipitation of precipitated phases, while unaffecting grain size. Unidirectional tensile stress caused directional growth of β phase([1010]), as well as rotation of weave towards the basal plane texture, resulting in namely stress orientation effect. Solute atoms diffused in the direction of tensile stress while vacancies moved perpendicular to the direction of tensile stress, resulting in PFZ at grain boundaries(157.06 nm). By contrast, cyclic stresses led to the growth of β phase in three directions([1010], [1100] and [0110]). The solute atoms and vacancies were uniformly distributed in the Mg matrix instead of directional diffusion, effectively reducing the width of PFZ(112.39 nm) at the grain boundary. These features significantly improved the mechanical properties of alloy specimens after cyclic stress creep aging when compared to unidirectional stress creep aging, with yield strength(YS), ultimate tensile strength(UTS), and elongation(EL) enhanced from 171.6 MPa, 305.5 MPa, and 4.4%to 174.8 MPa, 326.3 MPa, and 6.9%, respectively.
文摘采用光学显微镜和蠕变实验机研究Mg-9Gd-4Y-1Zn-0.5Zr合金在不同温度和应力下的高温蠕变行为。结果表明：在应力为70～130 MPa范围内,200℃时Mg-9Gd-4Y-1Zn-0.5Zr合金的蠕变应力指数n=1.63,蠕变机制为晶界滑动,250℃时蠕变应力指数n=2.63,蠕变机制为位错滑移;在蠕变温度为200～250℃范围内,应力分别为70、90、110和130 MPa时,合金的蠕变激活能Qc分别为108.5、118.9、127.6和134.3 k J/mol;随着温度和应力的增加,合金晶粒长大,合金的蠕变机制由晶界滑动控制转变为位错滑移控制。
