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FABRICATION OF HIGH STRAIN RATE SUPERPLASTIC ALLOYS USING INTENSE PLASTIC STRAINING

使用强塑性应变制造高应变率超塑合金

基本信息

批准号：
09555212
负责人：
NEMOTO Minoru
金额：
$ 6.66万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09555212/
关键词：
superplasticity equal-channel angular pressing microstructural evolution ultrafine grain sizes aluminum alloys intense straining grain growth TEM 高速超塑性 ECAE Al合金再結晶組織設計

项目摘要

The equal-channel angular (ECA) pressing is capable of introducing an ultrafine grain size into bulk materials and the precise nature of the microstructure is dependent upon the total strain introduced by the pressing, temperature and speed of pressing. When the strain is sufficiently high, it is possible to achieve very high tensile ductilities at high strain rates. It is noted that the use of different processing routes provides an opportunity to alter the shearing planes and shear directions within the sample and therefore to modify, in a favorable manner, the microstructures induced by ECA pressing. It is known that the combination of shear in three dimensional way is effective to increase the amount of misorientation formed during each pressing. The attained grain size is as small as 1.2 micrometers even in high purity aluminum. When the alloying elements are added, the attained grain size reduced appreciably. To increase the elevated temperature stability of fine grain size, whic … More h is a prerequisite for attaining high strain rate superplasticity, a fine dispersion of particles is required. The present results provide a very clear demonstration of refinement of grain size and resultant advantageous high strain rate superplasticity which may be achieved by ECA pressing and microstructural control in a typical commercial Al-Mg-Li-Zr alloy where precipitates are present to retain the ultrafine grain sizes even at high temperatures where diffusion is rapid. Similar grain refinement and high strain rate superplasticity are achieved also in a commercial Al-2004 alloy known as Supral 100 with a chemical composition of Al-6% Cu-0.4% Zr. Furthermore, the exceptionally high strain rate superplasticity of the Al-3%Mg-0.2%Sc alloy was achieved by ECA pressing at room temperature without the use of any intermediate heating. In the Al-Mg-Sc alloy, the migration of grain boundaries are suppressed by the fine dispersion Al_3 Sc phase and then enhancing the grain boundary sliding and the matrix is solution strengthened by Mg suppressing the dislocation glide in the grains. The present work also provides the potential for substantially increasing the viability of superplastic forming in the metal forming industry. Less

等通道转角（ECA）压制能够将超细晶粒尺寸引入到块体材料中，并且微观结构的精确性质取决于由压制、温度和压制速度引入的总应变。当应变足够高时，可以在高应变速率下实现非常高的拉伸延展性。应注意，使用不同的加工路线提供了改变样品内的剪切平面和剪切方向的机会，因此以有利的方式改变由ECA压制引起的微观结构。已知的是，以三维方式的剪切的组合对于增加在每次压制期间形成的取向差的量是有效的。即使在高纯铝中，所获得的晶粒尺寸也小至1.2微米。加入合金元素后，晶粒尺寸明显减小。为了增加细晶粒尺寸的高温稳定性， ...更多信息 H是获得高应变速率超塑性的先决条件，需要颗粒的精细分散。目前的结果提供了一个非常清楚的证明细化晶粒尺寸和所得的有利的高应变速率超塑性，这可以通过ECA压制和显微组织控制在一个典型的商业Al-Mg-Li-Zr合金，其中沉淀物存在，以保持超细晶粒尺寸，即使在高温下，扩散是快速的。类似的晶粒细化和高应变速率超塑性也在被称为Supral 100的具有Al-6%Cu-0.4%Zr的化学组成的商业Al-2004合金中实现。此外，在不使用中间加热的情况下，室温ECA挤压可使Al-3%Mg-0.2%Sc合金获得极高的应变速率超塑性。在Al-Mg-Sc合金中，细小弥散的Al_3Sc相抑制晶界的迁移，从而促进晶界的滑移，Mg抑制位错在晶内的滑移，使基体得到固溶强化。目前的工作也提供了潜在的大幅提高超塑性成形在金属成形工业的可行性。少