Equal Channel Angular Pressing of Metallic Powders for Nanostructured Materials

Author(s):  
Seung Chae Yoon ◽  
Hyoung Seop Kim
2007 ◽  
Vol 345-346 ◽  
pp. 173-176 ◽  
Author(s):  
Seung Chae Yoon ◽  
Do Minh Nghiep ◽  
Sun Ig Hong ◽  
Z. Horita ◽  
Hyoung Seop Kim

Manufacturing bulk nanostructured materials with least grain growth from initial powders is challenging because of the bottle neck of bottom-up methods using the conventional powder metallurgy of compaction and sintering. In this study, bottom-up type powder metallurgy processing and top-down type SPD (Severe Plastic Deformation) approaches were combined in order to achieve both full density and grain refinement of metallic powders. ECAP (Equal-Channel Angular Pressing), one of the most promising processes in SPD, was used for the powder consolidation method. For understanding the ECAP process, investigating the powder density as well as internal stress, strain and strain rate distribution is crucial. We investigated the consolidation and plastic deformation of the metallic powders during ECAP using the finite element simulations. Almost independent behavior of powder densification in the entry channel and shear deformation in the main deformation zone was found by the finite element method in conjunction with a pressure dependent material yield model. Effects of processing parameters on densification and density distributions were investigated.


2006 ◽  
Vol 503-504 ◽  
pp. 221-226 ◽  
Author(s):  
Seung Chae Yoon ◽  
Hyoung Seop Kim

In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve both full density and grain refinement of metallic powders with least grain growth, which was considered as a bottle neck of the bottom-up method using the conventional powder metallurgy of compaction and sintering. ECAP (Equal channel angular pressing), one of the most promising method in SPD, was used for the powder consolidation. In the ECAP process of not only solid but also powder metals, knowledge of the density as well as internal stress, strain and strain rate distribution is important for understanding the process. We investigated the consolidation, plastic deformation and microstructure evolution behavior of the metallic powders during ECAP using experimental and theoretical methods. Almost independent behavior of powder densification in the entry channel and shear deformation in the main deformation zone was found by the finite element method in conjunction with a pressure dependent material yield model. It was found that high mechanical strength could be achieved effectively as a result of the well bonded powder contact surface during ECAP process of gas atomized Al-Si powders. The SPD processing of powders is a viable method to achieve both fully density and nanostructured materials.


2007 ◽  
Vol 534-536 ◽  
pp. 253-256 ◽  
Author(s):  
Seung Chae Yoon ◽  
Sun Ig Hong ◽  
Soon Hyung Hong ◽  
Hyoung Seop Kim

In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve both full density and grain refinement of metallic powders with least grain growth, which is considered as a bottle neck of the bottom-up method that uses the conventional powder metallurgy of compaction and sintering. ECAP (Equal channel angular pressing), one of the most promising method in SPD, was used for the powder consolidation. In the ECAP process of not only solid but also powder metals, it is important to get a good understanding of the density as well as internal stress, strain and strain rate distribution. We investigated the consolidation, plastic deformation and microstructure evolution behavior of the metallic powders during ECAP using an experimental method. It was found that high mechanical strength could be achieved effectively due to the well bonded powder contact surface during ECAP process of gas atomized Al-Si powders. The experimental results show that SPD processing of powders is a viable method to achieve both fully density and nanostructured materials.


Author(s):  
Xiaojing Xu ◽  
Jinqi Cao

The preparation of dense bulk nanostructured materials is becoming an important research subject with the development of nanostructured materials. Equal Channel Angular Pressing (ECAP) is thought to be one of the major technologies to prepare bulk nanostructured or ultra-fine grained metals, which can improve the mechanical property of materials considerably, but its processing effect was affected by many factors, such as press route, angle of channels, etc. Since some questions in the procedure of ECAP were not understood clearly, the researchers have different judgments on these factors affecting the result of ECAP processing. There were few reports about the processing condition that affect the strain uniformity, most of which deal with only 1 and 2 passes of ECAP. In present paper, a model dealing with four connective channels which can implement the continuous 4 passes ECAP processing was established firstly, the finite element software, DEFORM-3D, was used to simulate the processing of ECAP to study how the processing condition (press route and structure of die such as the channel angle and inner-arc radius) to affect the strain uniformity. Results show that the influence of press route is associated with pressing passes. In term of 4 passes pressing, route Bc has a most uniform distribution of strain, while in term of 2 passes pressing, route C can get a good strain uniformity. In addition, with the increase of channel angle and inner-arc radius, the strain uniformity was also improved considerably. So to get the best strain uniformity all the above factors should be taken into consideration.


2003 ◽  
Vol 437-438 ◽  
pp. 89-92 ◽  
Author(s):  
Hyoung Seop Kim ◽  
Min Hong Seo ◽  
Chang Seok Oh ◽  
Sung Joon Kim

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