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通过改变定向凝固前的保温时间,研究热稳定处理对定向凝固Ti-46Al-0.5W-0.5Si(摩尔分数,%)合金组织和性能的影响。在稳定的温度梯度下(G=20K/mm),定向凝固启动前试样分别保温5、15、30、45和60min,然后试样以恒定的速度(v=30μm/s)进行定向凝固实验。测量定向凝固组织的一次枝晶间距(λ1)、二次枝晶间距(λ2)、层片间距(λL)和显微硬度(HV),并分析这些参数与热稳定处理时间(t)的关系。λ1、λ2和λL的值随着t的延长而增大,而HV则随着t的延长而减小。在定向凝固启动前,延长热稳定时间有助于获得良好的定向凝固组织,然而,过长的保温时间则会降低合金的力学性能。因此,需要优化定向凝固前的热稳定处理时间。根据实验结果,在当前实验条件下,定向凝固前热稳定处理时间选择30min,既能够获得良好的定向凝固组织,又能保持合金较高的力学性能。
By changing the holding time before directional solidification, the effect of thermal stabilization on the microstructure and properties of Ti-46Al-0.5W-0.5Si (mole fraction,%) alloy was investigated. The samples were incubated for 5, 15, 30, 45 and 60 min respectively after the directional solidification was started at a steady temperature gradient (G = 20K / mm). The specimens were then subjected to directional solidification at a constant velocity (v = 30 μm / s) . The primary dendrite spacing (λ1), secondary dendrite spacing (λ2), lamellar spacing (λL) and microhardness (HV) were measured and the relationship between these parameters and the thermal stabilization treatment time (t) . The values of λ1, λ2 and λL increase with the extension of t, while HV decrease with the extension of t. Extending the thermal stabilization time helps to obtain good directional solidification before the directional solidification is started. However, prolonged holding time will reduce the mechanical properties of the alloy. Therefore, there is a need to optimize the thermal stabilization process before directional solidification. According to the experimental results, under the current experimental conditions, the heat-stable treatment time before directional solidification is selected for 30 min, which can not only obtain good directional solidification structure, but also maintain the high mechanical properties of the alloy.