Strain-induced grain evolution in polycrystalline copper during warm deformation
- Univ. of Electro-Communications, Chofu, Tokyo (Japan). Dept. of Mechanical and Control Engineering
The evolution mechanisms of dislocation microstructures and new grains at high strains of above 4 were studied by means of multiple compression of a polycrystalline copper (99.99 pct). Deformation was carried out by multipass compression with changing of the loading direction in 90 deg in each pass at temperatures of 473 k TO 573 k (0.35 TO 0.42 t{sub M}) under a strain rate of 10{sup {minus}3} s{sup {minus}1}. The flow stresses increase to a peak followed by a work softening accompanied mainly by dynamic recrystallization (DRX) at 523 K to 573 K. In contrast, the steady-state-like flow appears at 473 K accompanied with the development of fine grains at strains as high as 4.2. The relationship of flow stress to the new grain size evolved can be expressed by a power law function with a grain size exponent of about {minus}0.35, which is different from {minus}0.75 for high-temperature FRX at above 0.5 T{sub m}. At 473 K, misorientations of deformation-induced dislocation subboundaries increase with increasing strain, finally leading to the evolution of new grains. It is concluded that the dynamic grain formation at 473 K cannot result from DRX, but from the evolution of deformation-induced dislocation subboundaries with high misorientations and, concurrently, the operation of dynamic recovery.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 316030
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 12 Vol. 29; ISSN 1073-5623; ISSN MMTAEB
- Country of Publication:
- United States
- Language:
- English
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