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Effects of Impurity Elements on the Hot Ductility of High Purity Iron Alloys

杂质元素对高纯铁合金热态塑性的影响

基本信息

批准号：
05452284
负责人：
ABIKO Kenji
金额：
$ 4.67万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05452284/
关键词：
High purity iron alloys Impurity element Tensile test Hot ductility Intergranular fracture Segregation at grain boundary Cavitation Mechanical property 高温変形

项目摘要

We have succeeded in the development of a ultra-high vacuum chamber for high temperature tensile test. The vacuum during testing is better than 10<@D1-7@>D1 torr ; the specimen can be quickly heated to a given temperature up to 1000ﾟC ; the accuracy of load can be controlled in (]SY.+-。[)50g.High purity Fe-S and Fe-P alloys with the compositions controlled in one ppm have been prepared to clarify the effects of sulphur and phosphorus on the hot ductility of high purity iron. Tensile test was performed at temperatures ranging from room temperature to 900ﾟC.The observations of microstructure and fracture surface, and the AES analysis of grain boundaries and void surfaces were also carried out to clarify the mechanism of the intrinsic effects. The main results obtained in the present study can be summarized as follows :1. High purity iron shows an excellent hot ductility, that is, reduction in area (RA) larger than 90%, at the test temperatures.2. Soluble sulphur of only 5 ppm causes a significant hot ductility drop of high purity iron near 650ﾟC.Increasing the soluble sulphur content further decreases the hot ductility and widens the temperature range of embrittlement. The embrittlement occurs by growth and coalescence of cavities nucleated at the grain boundaries with sulphur segregation. The segregated sulfur at grain boundaries facilitates the nucleation of cavities and the more segregation of sulphur on the cavity surfaces enhances the growth of cavities.3. The addition of phosphorus to high purity iron remarkably increases the elongation of iron to fracture at test temperatures above 500ﾟC.The phenomenon has been shown to be related with the effect of phosphorus on the dynamic recovery and recrystallization of iron.

我们成功地开发了用于高温拉伸试验的超高真空室。试验时真空度优于10<@D1-7@>D1 torr；试样可以快速加热到给定温度高达1000℃；负载精度可控制在（]SY.+- [）50g。制备了高纯度铁- s和铁- p合金，其成分控制在1 ppm，以阐明硫和磷对高纯铁热延展性的影响。拉伸试验在室温至900℃的温度下进行。通过显微组织和断口观察、晶界和空洞表面的原子发射光谱分析，阐明了内在效应的机理。本研究得到的主要结果可以总结如下：1。在测试温度下，高纯铁表现出优异的热延展性，即面积（RA）收缩率大于90%。5 ppm的可溶性硫会导致高纯度铁在650℃附近的热延展性显著下降。可溶性硫含量的增加进一步降低了材料的热塑性，扩大了脆化的温度范围。脆化是由在晶界处成核的空腔的生长和合并引起的，并伴有硫偏析。晶界处的偏析硫有利于空腔的成核，空腔表面的偏析硫越多，有利于空腔的生长。在500℃以上的测试温度下，高纯度铁中添加磷可以显著提高铁的断裂伸长率。这一现象与磷对铁的动态回收和再结晶的影响有关。