The role of bimodal grain size distribution in nanocrystalline shape memory alloys

Content Provider	Scilit
Author	Mikula, Jakub Quek, Siu Sin Joshi, Shailendra P. Wu, David T. Ahluwalia, Rajeev
Copyright Year	2018
Description	Journal: Smart Materials and Structures We report on a phase field simulation study of the effects of grain size and grain size distribution on martensitic transformations in shape memory alloys. Recent ex- perimental studies of polycrystalline shape memory alloys revealed interesting grain size effects when grain sizes are reduced to tens of nanometers. While small grain sizes yield superior mechanical strength, the material loses its shape memory prop- erty if grain sizes are smaller than some critical size. To reintroduce shape memory properties, and at the same time retain strong mechanical properties, we propose to introduce several large grains (much larger than the critical transformation grain size) amid the nano-sized grains, which yields a grain microstructure with a bimodal grain size distribution. A phase field model is adopted to simulate the martensitic transformation in polycrystals, to which excess grain boundary energy is introduced that suppresses martensitic transformation in the grain boundaries. We observe that simulated as-quenched microstructures of the bimodal grain size distribution may in a special case equilibrate as a phase composite (austenite + martensite). The spatial distribution of these phases and alloy functionalities (shape memory) may be controlled by the design of the grain size distribution. Loading and unloading simula- tions of the equilibrium martensitic microstructures show that the large grains enable martensitic detwinning to occur, hence reintroducing shape memory functionality to the nanocrystalline shape memory alloy.
Related Links	http://iopscience.iop.org/article/10.1088/1361-665X/aada30/pdf
ISSN	09641726
e-ISSN	1361665X
DOI	10.1088/1361-665x/aada30
Journal	Smart Materials and Structures
Issue Number	10
Volume Number	27
Language	English
Publisher	IOP Publishing
Publisher Date	2018-08-14
Access Restriction	Open
Subject Keyword	Journal: Smart Materials and Structures Metallurgy and Metallurgical Engineering Shape Memory Bimodal Grain Size Distribution
Content Type	Text
Resource Type	Article
Subject	Signal Processing Atomic and Molecular Physics, and Optics Mechanics of Materials Condensed Matter Physics Materials Science Electrical and Electronic Engineering Civil and Structural Engineering