定向凝固U720Li合金的高温塑性变形行为

doi:10.11900/0412.1961.2015.0374

金属学报 DOI: 10.11900/0412.1961.2015.0374

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定向凝固U720Li合金的高温塑性变形行为

高博¹,王磊¹,梁涛沙¹,刘杨¹,宋秀²,曲敬龙³

1. 东北大学
2. 东北大学材料与冶金学院
3. 北京钢铁研究总院高温材料研究所

PLASTIC DEFORMATION BEHAVIOR OF DIRECTIONALLY SOLIDIFIED U720Li SUPERALLOY AT ELEVATED TEMPERATURE

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摘要: 采用热模拟实验研究了定向凝固与等轴晶U720Li合金的高温塑性变形行为,利用OM,SEM和EBSD分析了不同变形条件下合金的组织特征及动态再结晶机制.结果表明,定向凝固与等轴晶合金的变形抗力均随变形温度升高而降低.定向凝固U720Li合金沿垂直柱状晶方向变形时变形抗力较低,枝晶间协调变形能力良好,未出现裂纹.与等轴晶合金相比,相同变形条件下定向凝固合金的动态再结晶组织均匀;高温塑性变形过程中,定向凝固合金的动态再结晶主要以晶界弓弯和位错塞积方式形核.定向凝固U720Li合金的变形激活能为766 kJ/mol,比等轴晶合金降低了38.6 %,定向凝固合金呈现出更好的热加工特性.

关键词 ：定向凝固, U720Li合金, 热加工塑性, 动态再结晶

Abstract：U720Li, a kind of precipitation type nickel-based superalloy, shows excellent mechanical properties at elevated temperature, which is also known as the difficult-to-deform alloy because of the high-alloying. To solve its deformation problem, new methods would be developed to enlarge the temperature deforming window and improve its plasticity. The hot compression deformation behaviors of directionally solidified and equiaxed grain U720Li alloys were studied by the MMS-300 testing system, as well as the dynamic recrystallization nucleation and growth mechanisms during the hot deformation were discussed. The microstructural characteristics of the alloy under different deformation conditions were examined using OM, SEM and EBSD. The results show that the deforming resistances of both directionally solidified and equiaxed grain U720Li alloys decrease with the increasing of deforming temperature. When the angle ? between the compression deforming direction and dendrite growth direction is 90°, the deforming resistance of directionally solidified U720Li alloy would be lower. With this direction, the coordination deformation between the dendrites becomes better and no crack can be found after deformation, which indicates that the deforming ability is best along ????90° and it can be considered as the optimal deforming direction for directionally solidified U720Li alloy. Compared with equiaxed grain alloy, directionally solidified U720Li alloy performs higher deformation ability and more homogenous microstructures. During the deformation of directionally solidified U720Li alloy, bulging nucleation of grain boundary migration and dislocation pile-up induced nucleation are found as the main mechanism for the nucleation of dynamic recrystallization. In addition, the deformation activation energy of directionally solidified U720Li alloy is 766 kJ/mol, which is 482 kJ/mol lower than that of equiaxed grain alloy, indicating the directional solidified U720Li alloy exhibits better hot-working plasticity.

Key words： directional solidification U720Li hot-working plasticity dynamic recrystallization

收稿日期: 2015-07-10

ZTFLH:

TG 319，TG113.25+3

基金资助:国家自然科学基金项目;国家自然科学基金项目;国家高技术研究发展计划项目

通讯作者: 王磊

Corresponding author: 磊王

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引用本文:

高博王磊梁涛沙刘杨宋秀曲敬龙. 定向凝固U720Li合金的高温塑性变形行为[J]. 金属学报, 10.11900/0412.1961.2015.0374.

链接本文:

https://www.ams.org.cn/CN/Y0/V/I/0

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