MICROSTRUCTURAL INVESTIGATION ON CAVITY NUCLEATION AT PRECIPITATIONS IN SUPERPLASTIC ALUNIMUM ALLOYS.

超塑铝合金沉淀时空穴成核的微观结构研究。

基本信息

批准号：
11650722
负责人：
IWASAKI Hajime
金额：
$ 1.92万
依托单位：
HIMEJI INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

The deformation behavior and cavitation characteristics were investigated at 613-693 K and at 10^<-4>-10^<-2>/s in Al-4.5Mg-0.09Si and Al-4.5Mg-0.2Si containing second phase particles of Mg_2Si. Both alloys showed elongation above 350% at 653 K and at 1O^<-3>/s. The 0.2Si alloy showed more cavitation development than the 0.09Si alloy. This indicates that the large addition of Si promotes cavity formation. It should be noted that microcavities were nucleated at the matrix/particle interfaces. The cavity growth rate of the 0.09Si alloy was the same as that of the 0.2Si alloy. On the other hand, the number of cavities for the 0.2Si alloy was much larger than that for the 0.09Si alloy. These results conclusively demonstrate that the addition of Si promotes cavity nucleation because of stress concentrations at the interfaces. Investigation of the sites for cavity nucleation revealed that the experimental critical particle size for cavity formation was in agreement with the critical diffusion length. The intragranular particles tended to nucleate cavities compared to the intergranular particles. Furthermore, the critical particle size for cavity nucleation was investigated using high-strain-rate superplastic aluminum matrix composite containing Si_3N_4 particles. As results, the critical particle size for cavity nucleation was in a good agreement with theoretical value estimated from Stwell's equation giving the critical strain rate and from Mabuchi's equation giving the critical stress. In a presence of small amount of liquid, however, the experimental critical particle size was larger than the theoretical values.

在613-693 K和10^<-4> -10^<-2>/s的Al-4.5MG-0.09SI和Al-4.5MG-0.2SI中，研究了变形行为和空化特性，含有MG_2SI的第二相颗粒。两种合金在653 K和1O^<-3>/s时均显示出高于350％的伸长率。 0.2SI合金比0.09SI合金显示出更多的气蚀发育。这表明SI的大量添加促进了腔形成。应该注意的是，在基质/粒子界面上将微腔成核。 0.09SI合金的空腔生长速率与0.2SI合金相同。另一方面，0.2SI合金的空腔数远大于0.09Si合金的腔数。这些结果最终表明，由于界面处的应力浓度，SI的添加促进了空腔成核。对空腔成核位点的研究表明，腔形成的实验临界粒径与临界扩散长度一致。与晶间颗粒相比，粒内颗粒倾向于成核腔。此外，使用含有si_3n_4颗粒的高材料速率铝制基质复合材料研究了腔成核的临界粒径。结果，腔成核的临界粒径与从斯特韦尔方程估计的理论值吻合良好，从而给出了临界应变速率和mabuchi's方程，从而给予临界应力。但是，在少量液体的情况下，实验临界粒径大于理论值。