Investigation of PCTIG, CCTIG and MMA Welding on Powder Metallurgy Aluminium Specimen Processed through Equi-Channel Angular Pressing (ECAP)

In powder metallurgy (PM), severe plastic deformation (SPD) is a well-known technological solution to achieve interesting properties. However, the occurrence of pores in the final product may limit these properties. Also, for a given type of microstructure, the stereometric parameters of the pore structures, such as shape (represented by Aspect and Dcircle) and distribution (fshape, and fcircle), decisively affect the final properties. The influence of different processing routes (pressing, sintering and equal channel angular pressing (ECAP)) on pore structures in an aluminum PM alloy is discussed. The nature of porosity, porosity evolution and its behavior is explored. The correlation between pore size and morphology is also considered. The final pore structure parameters (Aspect, Dcircle, fshape, and fcircle) of studied aluminum alloys produced by different processing routes depends on the different formation routes.

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Achieving Both Powder Consolidation and Grain Refinement for Bulk Nanostructured Materials by Equal-Channel Angular Pressing

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.345-346.173 ◽

2007 ◽

Vol 345-346 ◽

pp. 173-176 ◽

Cited By ~ 1

Author(s):

Seung Chae Yoon ◽

Do Minh Nghiep ◽

Sun Ig Hong ◽

Z. Horita ◽

Hyoung Seop Kim

Keyword(s):

Plastic Deformation ◽

Finite Element ◽

Powder Metallurgy ◽

Grain Refinement ◽

Nanostructured Materials ◽

Equal Channel Angular Pressing ◽

Bottom Up ◽

Powder Consolidation ◽

Metallic Powders ◽

Angular Pressing

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.

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Compaction of Ti-6Al-4V Powder by ECAE with Back-Pressure

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.29-30.33 ◽

2007 ◽

Vol 29-30 ◽

pp. 33-36 ◽

Cited By ~ 2

Author(s):

Rimma Lapovok ◽

Dacian Tomus ◽

Barry C. Muddle

Keyword(s):

Powder Metallurgy ◽

Hydrostatic Pressure ◽

Relative Density ◽

Shear Deformation ◽

Vickers Hardness ◽

Room Temperature ◽

Low Cost ◽

Hot Isostatic Pressing ◽

Back Pressure ◽

Angular Pressing

Powder metallurgy is widely used to produce alloys with low cost of production. The main drawback using powders is the level of residual porosity of final product which often implies the application of a complicated and costly hot isostatic pressing process. However, this issue can be overcome by using equal channel angular pressing (ECAE) with back pressure (BP). The use of severe shear deformation, with imposed hydrostatic pressure, allows a reduction in the range of compaction temperatures compare to those used in conventional practice. The compaction of Ti-6Al-4V powder by the ECAE method has been investigated. The compaction has been performed at temperatures starting from room temperature (RT) and increasing up to 400°C with various back pressures ranging from 0 to 350MPa. A billet processed by ECAE with 43MPa back-pressure at 400°C was found to have improved relative density of 97.5% and increased Vickers hardness of 369HV, compared to values of 96.7% and 325HV respectively obtained at RT. A relative density of 98.2% and 426HV hardness were measured for billets processed with BP = 262MPa at 400°C. A fully compact billet was obtained by applying 350 MPa of BP at 400°C.

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