ABSTRACT

Dendrite coherency or dendrite impingement is an important factor for determining solidification microstructure and casting defects of alloys. In this research, the effect of various cooling rates and Al-5Ti-1B grain refiner contents on the dendrite coherency point (DCP) characteristics of an Al-Si-Mg alloy designated as A357 has been studied. The results showed that both mentioned parameters have a significant influence on DCP of this alloy. Increasing the cooling rate from 0.15 to 1.0 °C/s and the grain refiner content from 0.0 to 3 wt. % increased the solid fraction in where dendrite coherency occurs. Moreover, enhancement of the cooling rate and grain refiner could increase the difference between the liquidus and coherency temperatures (T_N–T_DCP), about 27 and 26 °C, respectively. The dendrite coherency time decreased by increasing the cooling rate and increased by increasing the grain refiner content.

摘要

枝晶相干性或枝晶冲击是确定合金的凝固组织和铸造缺陷的重要因素。在这项研究中，研究了各种冷却速度和Al-5Ti-1B晶粒细化剂含量对Al-Si-Mg合金A357的枝晶相干点（DCP）特性的影响。结果表明，上述两个参数均对该合金的DCP有重要影响。将冷却速率从0.15提高到1.0°C / s，将晶粒细化剂的含量从0.0提高到3 wt。％增加了发生枝晶相干的固体部分。此外，增强的冷却速度和晶粒细化剂的可能增加（T液相线和一致性温度之间的差异_Ñ -T _DCP），分别约在27和26°C。通过提高冷却速率，枝晶相干时间减少，而通过增加晶粒细化剂含量，枝晶相干时间增加。