沙漏挤压镦粗复合加工技术

本文研究了一种新的晶粒细化方法 :沙漏挤压工艺。这种工艺是在一定温度下通过对材料进行反复挤压产生大的塑性变形 ,同时进行动态再结晶而使材料得到细化。本文对铸态 Zn- Al合金进行了实验 ,初步研究了沙漏挤压工艺对于材料组织和性能的影响。实验结果表明 :沙漏挤压工艺能够有效的细化晶粒 ,使材料获得均匀的等轴细晶组织和优良的综合性能 ,并有助于实现高应变速率超塑性     

Improvement of superplasticity in AA5083 by equal channel angular extrusion and rolling

Al–Mg–Mn alloy AA5083 has been processed by equal channel angular extrusion (ECAE) followed by hot and cold rolling. The grain structure, crystallographic texture, intermetallic phases and superplasticity were investigated and compared with a conventionally hot and cold rolled AA5083 sheet. The intensive shear strain in ECAE has a very strong breakdown effect on the dendritic cast structure, which effectively changes the volume fraction and size of the intermetallic particles that provide particle stimulated nucleation upon recrystallisation. Consequently, the combination of ECAE and rolling leads to a finer and more thermally stable grain structure, with fewer very coarse constituent particles, resulting in a significant improvement in superplasticity through enhanced grain boundary sliding, with retarded formation and linkage of cavities.     

超塑性三十年:回顾与展望

1986年在东北大学的访问为我提供了一次介绍和讨论超塑性这一科学问题的机会.现在,三十年已经过去,在此我们对这个科学领域的发展做以回顾与展望..     

Cu－Zn－Al形状记忆合金的超塑性研究

用超塑性拉伸试验方法，研究了加入晶粒细化剂Ｚｒ的冷变形Ｃｕ－２２．６７％Ｚｎ－４．５９％Ａｌ形状记亿合金的短暂超塑性变形．在６００℃，以初始应变速率ε＝５．５５×１０－４ｓ－１进行拉伸试验可获得优良的超塑性性能，延伸率δ＝４６０％．超塑性变形过程中激活能为７４．４ＫＪ／ｍｏｌ，与铜沿晶自扩散激活能值接近．从而认为该合金的超塑性变形机制为晶界的滑移和迁移过程，这一结论与金相观察及断口分析相一致     

稀土对Zn—5Al合金超塑性的影响

在Ｚｎ－５％Ａｌ合金中添加适量稀土元素，可形成Ａｌ２ＣｅＺｎ２，ＣｅＺｎ３等化合物，提高合金的超塑变形速率和伸长率，加入过量的稀土则对超塑性能有不利的影响。     

轧制AZ91镁合金超塑性研究

研究了轧制态AZ91镁合金在实验温度为350℃－425℃（0．67Tm-0.76Tm）以及应变速率为10^-3s^-1－10^0s^-1下的超塑性变形能力及其特征。实验发现，轧制态AZ91镁合金在350℃（0.67Tm）以及应变速率为10^-3s^－1时获得最大延伸率455．05％，应变速率敏感系数达到0．64。通过分析表明，高应变速率下的超塑性变形过程中主要的变形机制为晶界滑移机制，但其主要的协调机制则是孔洞扩散聚集机制。     

高温氧化对钛合金超塑性能的影响

研究了Ti-6Al-4V合金在800℃、850℃和900℃高温条件下进行拉伸试验时空气氧化对超塑性能的影响。通过光学显微镜、扫描电镜和X射线衍射分析了该钛合金氧化层的微观形貌和成分组成，并研究其在高温拉伸下的氧化机理。结果表明，高温氧化导致该合金在高温拉伸过程中表面产生氧化层，而在拉伸应力作用下氧化层断裂并向基体扩展，从而严重降低了Ti-6Al-4V合金的超塑性，但不会影响其抗拉强度及屈服强度。     

Superplasticity of a SiC particulate-reinforced 6A02AI matrix composite

The superplastic characteristics of a 15% (volume fraction) SiCp (14 μm)/6A02A1 composite, fabricated by stirring casting and cold-rolling after extrusion with a low extrusion ratio of 10:1 and hot-rolling, were investigated. The composite exhibits a tensile elongation of 250% at an initial strain rate of 8.9 x 10-4 s-l and at 833 K where an appropriate amount of liquid phase is presented in the composite. The superplastic deformation is uniform and the strain hardening exponent 2is as high as 1.6. The fracture surface is intergranual and the superplastic deformation mechanism of the composite is considered to be grain boundary (interface) sliding accommodated by an appropriate amount of liquid phase.     

Mechanism for phase boundary sliding and its relevance to diffusion-solution zone in SPD

1　ＩＮＴＲＯＤＵＣＴＩＯＮＳｉｎｃｅｔｈｅｄｉｓｃｏｖｅｒｙｏｆｓｕｐｅｒｐｌａｓｔｉｃｉｔｙ ,ｐｅｏｐｌｅｈａｖｅｉｎｖｅｓｔｉｇａｔｅｄｈｕｎｄｒｅｄｓｏｆｓｕｐｅｒｐｌａｓｔｉｃｍａｔｅｒｉａｌｓｉｎｃｌｕｄｉｎｇｐｏｌｙｃｒｙｓｔａｌｃｅｒａｍｉ     

异种钢材超塑性扩散连接接头的热处理

通过对W6Mo5Cr4V2和45钢的超塑性扩散连接接头的热处理试验,分析了热处理对连接接头的组织性能影响。结果表明:接头经580℃预热+800℃预热+1200℃×(5～10)min淬火+560℃×1h回火3次热处理后,其界面两侧的显微组织得到改善,显微硬度不再有明显的硬度低谷区和硬度高峰区。