Investigation of specimen size effects by in-situ microcompression of equal channel angular pressed copper

Journal Article · Wed Sep 30 00:00:00 EDT 2015 · Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing

DOI:https://doi.org/10.1016/j.msea.2015.09.110· OSTI ID:1411693

Howard, C. ^[1]; Frazer, D. ^[1]; Lupinacci, A. ^[1]; Parker, S. ^[1]; Valiev, R. Z. ^[2]; Shin, C. ^[3]; William Choi, B. ^[4]; Hosemann, P. ^[1]

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1. Univ. of California, Berkeley, CA (United States)
2. Ufa State Aviation Technical Univ., Ufa (Russia); Saint Petersburg State Univ., Saint Petersburg (Russia)
3. Myongji Univ., Yongin (Republic of Korea)
4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Here, micropillar compression testing was implemented on Equal Channel Angular Pressed copper samples ranging from 200 nm to 10 µm in side length in order to measure the mechanical properties yield strength, first load drop during plastic deformation at which there was a subsequent stress decrease with increasing strain, work hardening, and strain hardening exponent. Several micropillars containing multiple grains were investigated in a 200 nm grain sample. The effective pillar diameter to grain size ratios, D/d, were measured to be between 1.9 and 27.2. Specimens having D/d ratios between 0.2 and 5 were investigated in a second sample that was annealed at 200 °C for 2 h with an average grain size of 1.3 µm. No yield strength or elastic modulus size effects were observed in specimens in the 200 nm grain size sample. However work hardening increases with a decrease in critical ratios and first stress drops occur at much lower stresses for specimens with D/d ratios less than 5. For comparison, bulk tensile testing of both samples was performed, and the yield strength values of all micropillar compression tests for the 200 nm grained sample are in good agreement with the yield strength values of the tensile tests.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1411693
• Report Number(s): LLNL-JRNL-736666
• Journal Information: Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing, Vol. 649, Issue C; ISSN 0921-5093
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Microcompression tests
Scaling effects
Mechanical properties
Grain size