低偏析異質籽晶制備單晶高溫合金的籽晶融合區(qū)形成機制研究

低偏析異質籽晶制備單晶高溫合金的籽晶融合區(qū)形成機制研究Formation Mechanism of Fusion Zone in Growth of Single Crystal Superalloy with Low Segregated Heterogeneous Seed

本文采用低偏析異質籽晶法研究了定向凝固制備單晶高溫合金的籽晶融合區(qū)形成機制，結果表明：籽晶回熔平衡界面前沿存在一個無微觀偏析的融合區(qū)，該區(qū)域是凝固界面發(fā)生平面狀-胞狀失穩(wěn)轉變的過渡區(qū)。增加籽晶合金中W含量或提高定向凝固速率均會促進凝固界面的平面狀-胞狀失穩(wěn)轉變，且凝固速率的影響更顯著。相比于傳統(tǒng)籽晶法，低偏析異質籽晶融合區(qū)內的平界面凝固能有效避免籽晶回熔界面的枝晶熔斷和成分過冷導致雜晶形核，從而提高鑄件質量。

In order to investigate the non-steady state process of interface pattern in the growth of single crystal superalloy with low segregated heterogeneous seeds, Ni-based single crystal superalloy was prepared by high rate solidification (HRS) method in the dual heating zone furnace. The melt-back zone of seeds were investigated systematically, and the results showed that a fusion zone without segregation exists in front of the melt-back equilibrium interface of seeds, in which solidification interface transited from planar to cellular. Further experiments showed that increasing the W content of seeds or the solidification rate can both accelerate the whole non-steady transition process and make fusion zone shrink. Compared with the traditional seeding method, the low segregated heterogeneous seeding technique can increase the casting yield by avoiding the nucleation of stray grains around the melt-back equilibrium interface, which caused by the pinched-off secondary dendrites and constitutional undercooling.

全文下載：https://pan.baidu.com/s/1b9YuWQ