Matrix-precipitate interface-induced martensitic transformation within nanoscale phase field approach: Effect of energy and dimensionless interface width
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The Department of Aerospace Engineering seeks to instruct the design, analysis, testing, and operation of vehicles which operate in air, water, or space, including studies of aerodynamics, structure mechanics, propulsion, and the like.
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The Department of Aerospace Engineering was organized as the Department of Aeronautical Engineering in 1942. Its name was changed to the Department of Aerospace Engineering in 1961. In 1990, the department absorbed the Department of Engineering Science and Mechanics and became the Department of Aerospace Engineering and Engineering Mechanics. In 2003 the name was changed back to the Department of Aerospace Engineering.
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1942-present
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- Department of Aerospace Engineering and Engineering Mechanics (1990-2003)
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- College of Engineering (parent college)
- Department of Engineering Science and Mechanics (merged with, 1990)
Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.
For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.
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Abstract
Martensitic transformation induced by the matrix-precipitate interface (or other internal surfaces) for single and two martensitic variants is studied using a thermodynamically consistent multiphase phase field approach. Three order parameters are considered; two of them describe the austenite (A) ↔ martensite (M) and variant Mi ↔variant Mj transformations in a matrix, and the third one describes the finite width matrix - non-transforming precipitate interface. The energy of the matrix-precipitate interface reduces during A→M phase transformation from the value for energy of A-precipitate interface, γA, to value for energy of M-precipitate interface, γM, due to its dependence on the order parameter related to the austenite↔martensite transformation. Such an interface increases the temperature for barrierless martensite nucleation well above the critical temperature for A→M transformation. The nucleation temperatures strongly depend on the ratio Δ¯ of the widths of the matrix-precipitates interface and A−M interface. New “phase diagram” for transformation temperatures between austenite, martensite, and premartensite versus Δ¯ has been presented for neglected mechanics for two cases when magnitude of Δγ=γM−γA is larger than the energy of the A−M interface (0.2 N/m). For Δγ=−0.5 N/m, below a critical width ratio Δ¯*, a layer of premartensite appears jump-like within the matrix-precipitate interface and progresses with reducing temperature, until it loses its stability and jump-like transforms to complete martensite in the entire matrix. However, for Δ¯≥Δ¯*, the entire matrix transforms to martensite without any premartensite. For Δγ=−0.3 N/m, no premartensite appears and the A matrix completely transforms into M at lower temperatures that the case with Δγ=−0.5 N/m. The combined effect of the energy of the matrix-precipitate interface, Δ¯, precipitation-induced misfit strains, and applied displacements on the boundary of the sample on nucleation of martensite and complex microstructure evolution in the systems with a single and two martensitic variant(s) is studied. Obtained results are important for controlling cyclic martensitic transformations in shape memory and elastocaloric alloys and designing alloys with desired characteristics of martensitic transformations.
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This is a manuscript of an article published as Basak, Anup, and Valery I. Levitas. "Matrix-precipitate interface-induced martensitic transformation within nanoscale phase field approach: Effect of energy and dimensionless interface width." Acta Materialia (2020). DOI: 10.1016/j.actamat.2020.02.047. Posted with permission.