Abstract

The kinetics of primary α-Ti colony/Widmanstätten plate growth from the β are examined in Ti-6246, comparing a simple quasi-analytic model to experiment. The plate growth velocity depends sensitively both on the diffusivity D(T) of the rate-limiting species and on the supersaturation around the growing plate. These result in a maxima in growth velocity around 40 K below the transus, once sufficient supersaturation is available to drive the plate growth. In Ti-6246, the plate growth velocity was found to be around 0.32 μm min⁻¹ at 850 °C, which was in good agreement with the model prediction of 0.36 μm min⁻¹. The solute field around the growing plates, and the plate thickness, was found to be quite variable, due to the intergrowth of plates and soft impingement. This solute field was found to extend to up to 30 nm, and the interface concentration in the β was found to be around 6.4 at. pct Mo. It was found that the increasing O content from 500 to 1500 wppm will have minimal effect on the plate lengths expected during continuous cooling; in contrast, Mo approximately doubles the plate lengths obtained for every 2 wt pct Mo reduction. Alloys using V as the β stabilizer instead of Mo are expected to have much faster plate growth kinetics at nominally equivalent V contents. These findings will provide a useful tool for the integrated design of alloys and process routes to achieve tailored microstructures.

中文翻译：

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钛合金中初生Alpha板生长的动力学

抽象的

在Ti-6246中检查了从β产生的主要α -Ti菌落/Widmanstätten平板的动力学，并比较了简单的准分析模型和实验。板的生长速度敏感地取决于限速物种的扩散率D（T）和生长板周围的过饱和度。一旦有足够的过饱和度来驱动平板生长，这些将导致最高的生长速度低于孔眼以下40K。所得的Ti-6246，板生长速度被发现是0.32左右μ米分钟^-1在850℃，这是在0.36的模型预测一致μ米分钟^-1。发现由于板块的共生和软碰撞，在生长板块周围的溶质场和板块厚度变化很大。发现该溶质场扩展至高达30 nm，并且发现β中的界面浓度约为6.4 at。已经发现，O含量从500 wppm增加到1500 wppm时，对连续冷却过程中预期的板长影响最小。相反，每减少2 wt％Mo，Mo会使获得的板长大约增加一倍。以V为β的合金在名义上当量的V含量下，用稳定剂代替Mo可以使板的生长动力学更快。这些发现将为合金和工艺路线的集成设计提供有用的工具，以实现量身定制的微观结构。