ABSTRACT

The present work describes the challenges and methodology used to measure transient temperatures during solidification of an Al-Cu–Ag-TiB₂ alloy. Transients were measured using multiple thermocouples embedded in four different casting geometries. Solidified microstructures and the related morphologies in the regions surrounding the thermocouple tips were empirically related to the calculated cooling rates. The relation incorporates the grain refiner (TiB₂) level and an approximation of the alloy-specific growth restriction factor. Results indicate that the measured grain sizes ($d$) of the primary α-Al phase for all sampled material is highly correlated to initial solidification cooling rates ($\dot{T}$) ranging from 0.02 to 2.08°C/s as $d\left(\mu m\right)\approx \frac{55.0\pm 9.2}{{\left[4.5\right]}^{1/3}}+\frac{1370\pm 120}{85\cdot {\dot{T}}^{1/2}}$

Micro-computed tomography confirms that the primary phase observed using standard metallography solidifies with equiaxed grains in the presence of such thermal gradients.

摘要

目前的工作描述了用于测量 Al-Cu-Ag-TiB ₂合金凝固过程中瞬态温度的挑战和方法。使用嵌入四种不同铸件几何形状的多个热电偶测量瞬态。热电偶尖端周围区域的凝固微观结构和相关形态根据经验与计算出的冷却速率相关。该关系包含晶粒细化剂 (TiB ₂ ) 水平和合金特定生长限制因子的近似值。结果表明，测得的晶粒尺寸 ($d$) 所有样品材料的初生 α-Al 相与初始凝固冷却速率高度相关 ($\dot{吨}$) 范围从 0.02 到 2.08°C/s 作为 $d\left(\mu 米\right)\approx \frac{55.0\pm 9.2}{{\left[4.5\right]}^{1/3}}+\frac{1370\pm 120}{85\cdot {\dot{吨}}^{1/2}}$

显微计算机断层扫描证实，在这种热梯度存在的情况下，使用标准金相观察到的主相凝固为等轴晶粒。