Effect of Heterophase Interfaces on Microstructure and Crystallographic Texture Evolution During Rolling of Directionall
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TRODUCTION
DETAILED studies over the past decades have shown that deformation of ultrafine grained (UFG) and nanocrystalline (NC) face-centered cubic (FCC) metals and composites is strongly influenced by the enhanced interaction of defects with grain boundaries (GBs) and heterophase interfaces.[1–10] In single-phase UFG and NC metals, GBs control the nucleation and propagation of dislocations.[2,5] For example, below a critical grain size, depending on the stacking fault energy (SFE) of the metal, partial dislocations become the prominent strain carriers.[4] Such transition in deformation mechanism in NC metals can influence the crystallographic texture. For instance, Skrotzki et al.[7] and Gu et al.[8] have shown that Brass-type texture can develop in medium and high-SFE metals and alloys with NC and UFG grain size due to dominance of partial slip activity. A similar behavior was also observed for multiphase materials. Below a critical length scale, the heterophase interfaces could strongly influence the deformation characteristics of the constituent phases. The
JIEHUA LI is with the Institute of Casting Research, Montanuniversita¨t Leoben, Leoben, 8700, Austria. Contact e-mail: [email protected] JUN LI is with the Department of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai, 200240, China. OLIVER RENK, REINHARD PIPPAN, and PRADIPTA GHOSH are with the Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences, 8700, Leoben, Austria. Contact e-mail: [email protected] Manuscript submitted April 15, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
accumulative roll bonding of Cu-Nb has shown that until a layer thickness of 1 lm the crystallographic texture of Cu and Nb resembles the typical rolling texture of their monolithic counterparts; however, for layer thickness of the phases between 60 and 500 nm, where nearly one grain spans across the layer thickness, the neighboring Cu and Nb grains develop a special orientation relationship close to {338}h443i Cu // {112}h110i Nb.[11] For rolling below a layer thickness of 60 nm several twins are formed inside the Cu grains and the orientation relationship changed to {551}h11 10i Cu // {112}h110i Nb. Another heterophase system widely studied to unravel interface effects is the Ag-Cu eutectic alloy. Bulk texture measurements on Ag-Cu eutectic alloy rolled to 75 to 90 pct thickness reduction showed a similar Brass-type texture for both phases.[12] This observation is interesting because coarse-grained Cu usually develops a Copper-type texture for a similar amount of deformation.[13–15] Based on TEM analysis of the initial and final microstructure and Visco Plastic Self Consistent (VPSC) simulations, it was proposed that the transmission of twins across Ag-Cu interfaces, which have a cube-oncube orientation relation with {111} interface planes, stimulates the development of similar Brass-type texture in both phases.[12,16] However, a more detailed analysis of the interfaces showed that two different interface struct
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