Durability of Graphite Films in Plastic Deformation

1975 ◽  
Vol 97 (2) ◽  
pp. 289-294 ◽  
Author(s):  
J. A. Schey ◽  
A. H. Lonn
Keyword(s):  
Plastic Deformation ◽  
Plane Strain ◽  
Solid Lubricant ◽  
Plane Strain Compression ◽  
Sensitive Indicator ◽  
Force Measurements ◽  
Ring Compression ◽  
Tool Surface ◽  
Edge Profile ◽  
Repeated Contact

The ability of solid lubricant (graphite) films to withstand repeated contact with a deforming cold or hot aluminum workpiece was investigated by three techniques. Ring compression very readily indicated the gradual wear of the film, but sliding at the interface was limited and tendencies to tool pick-up did not show up. Plane strain compression was much more useful in this respect; changes in the edge-profile of the compressed zone proved to be a sensitive indicator of friction, obviating the need for force measurements. Twist compression imposed the most severe conditions. In all instances, a sandblasted tool surface provided better lubricant retention than a polished one.

scholarly journals Analysis and Characterization on Dynamic Recrystallization in Casting AZ31 Mg Alloys Under Plane Strain Compression

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 522
Author(s):  
Li Xu ◽  
Minghua Xiang ◽  
Jun Wang ◽  
Jun Zhang ◽  
Chenning Wang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Plane Strain ◽  
Rate Sensitivity ◽  
Local Stress ◽  
Plane Strain Compression ◽  
Mg Alloys ◽  
Coarse Grained ◽  
Compression Tests

Studies on twinning, twin-induced dynamic recrystallization (TDRX), and their temperature and strain rate dependences are of considerable significance to the ultimate strength and plastic formability of the coarse-grained Mg alloys during severe plastic deformation. Plane strain compression tests were conducted on the parallelepiped samples of casting AZ31 Mg alloys. The twinning and recrystallization behaviors close to and away from the crack boundaries were characterized using electron backscatter diffraction. The results show: (1) with increasing strain rate for tests, the extension twin proliferates significantly. Due to the local stress concentration, the TDRX is more active in the area close to the crack tip and exhibits the positive strain-rate sensitivity as twinning; (2) the TDRX is not only stress-favored but also closely links to the temperature. However, the TDRX is not utterly proportional to the temperature. Compared to 400 °C, 300 °C is more beneficial to the TDRX, achieving the higher strength and plastic deformability. The main reason is that the higher strain-hardening rate and flow stress at the higher strain rate and lower temperature motivates the transformation from twinning to the fine twin-walled grains more efficiently, and the stress-favored TDRX is crucial to refine grains and continue plastic deformation for the casting Mg alloys with coarse grains.

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