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研究定向凝固条件下凝固参数(生长速率v和温度梯度G)对Mg-2.35Gd合金显微组织及室温力学性能的影响。采用金属液淬技术,在温度梯度G为20、25、30 K/mm,生长速率v为10~200μm/s条件下通过高梯度Bridgman定向凝固炉制备试样。研究表明,实验合金的显微组织均为胞晶组织,胞晶间距λ随温度梯度和生长速率的增大而减小,其非线性拟合关系分别为λ=136.216v~(-0.2440)(G=30 K/mm)、λ=626.5630G~(-0.5625)(v=10μm/s),均与Trivedi模型较吻合。随温度梯度和生长速率的增大,合金室温抗拉强度逐渐提高,伸长率逐渐降低。同时,合金室温抗拉强度高于相同冷却速率条件下自由凝固试样的室温抗拉强度。
The effects of solidification parameters (growth rate v and temperature gradient G) on the microstructure and room-temperature mechanical properties of Mg-2.35Gd alloy were investigated under directional solidification conditions. The samples were prepared by high-gradient Bridgman directional solidification furnace under the condition of temperature gradient G of 20, 25, 30 K / mm and growth rate v of 10 ~ 200μm / s by metal liquid quenching technology. The experimental results show that the microstructure of the alloy is mesocrystalline, the lattice spacing λ decreases with the increase of temperature gradient and the growth rate, and the nonlinear fitting relationship is λ = 136.216v -0.2440 ( G = 30 K / mm), λ = 626.5630G ~ (-0.5625) (v = 10μm / s), all agree well with the Trivedi model. With the increase of temperature gradient and growth rate, the tensile strength at room temperature gradually increases and the elongation decreases gradually. At the same time, the room temperature tensile strength of the alloy is higher than the room temperature tensile strength of the free-setting sample under the same cooling rate.