Adjoint model for estimating material parameters based on microstructure evolution during spinodal decomposition

By means of the combined model, i.e., the phase-field model with finite interface dissipation in combination with the modified Cahn–Hilliard model, together with the materials parameters comprehensively verified in monolithic c-TiAlN coatings, the microstructure evolution in multilayer c-Ti[Formula: see text]Al[Formula: see text]N/TiN coatings annealed at [Formula: see text]C was quantitatively simulated by directly comparing with the experimental data. The sharp interface between c-TiN and c-Ti[Formula: see text]Al[Formula: see text]N layers in the as-deposited state was found to change into a diffuse one, which can act as highly effective obstacles against dislocation motion. Moreover, the simulations indicate that the spinodal decomposition occurs in the Ti[Formula: see text]Al[Formula: see text]N layer and the decomposed layer becomes thinner, which is in good agreement with the experimental observation. In addition, the effect of modulation period and modulation ratio on microstructure evolution in c-Ti[Formula: see text]Al[Formula: see text]N/TiN coating was further studied. The relatively smaller modulation period can generate more layers in the real scale of coatings, which can help to strengthen the coatings due to refinement of grains and restriction of dislocations. As for the modulation ratio, when the value decreases from 5:1 to 1:1, Ti atoms in the decomposed layer disappear faster. A further extension into a larger-sized simulation was also performed.

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Microstructure Evolution and Mechanical Properties of Melt Spun Skutterudite-based Thermoelectric Materials

Materials ◽

10.3390/ma13040984 ◽

2020 ◽

Vol 13 (4) ◽

pp. 984 ◽

Cited By ~ 3

Author(s):

Huiyuan Geng ◽

Jialun Zhang ◽

Tianhong He ◽

Lixia Zhang ◽

Jicai Feng

Keyword(s):

Mechanical Properties ◽

Spinodal Decomposition ◽

Microstructure Evolution ◽

Thermoelectric Materials ◽

High Performance ◽

Melt Spinning ◽

Bending Strength ◽

Annealed Sample ◽

Submicron Scale ◽

Spinning Process

The rapid solidification of melt spinning has been widely used in the fabrication of high-performance skutterudite thermoelectric materials. However, the microstructure formation mechanism of the spun ribbon and its effects on the mechanical properties are still unclear. Here, we report the microstructure evolution and mechanical properties of La–Fe–Co–Sb skutterudite alloys fabricated by both long-term annealing and melt-spinning, followed by sintering approaches. It was found that the skutterudite phase nucleated directly from the under-cooled melt and grew into submicron dendrites during the melt-spinning process. Upon heating, the spun ribbons started to form nanoscale La-rich and La-poor skutterudite phases through spinodal decomposition at temperatures as low as 473 K. The coexistence of the micron-scale grain size, the submicron-scale dendrite segregation and the nanoscale spinodal decomposition leads to high thermoelectric performance and mechanical strength. The maximum three-point bending strength of the melt spinning sample was about 195 MPa, which was 70% higher than that of the annealed sample.

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Modeling of Microstructure Evolution of Ti6Al4V for Additive Manufacturing

Metals ◽

10.3390/met8080633 ◽

2018 ◽

Vol 8 (8) ◽

pp. 633 ◽

Cited By ~ 20

Author(s):

Emilio Salsi ◽

Michele Chiumenti ◽

Miguel Cervera

Keyword(s):

Microstructure Evolution ◽

Manufacturing Processes ◽

Material Parameters ◽

Proposed Model ◽

Engineering Problems ◽

Microstructural Model ◽

Initial Content ◽

Fast Cooling ◽

Simulation Results ◽

Am Processes

AM processes are characterized by complex thermal cycles that have a deep influence on the microstructural transformations of the deposited alloy. In this work, a general model for the prediction of microstructure evolution during solid state transformations of Ti6Al4V is presented. Several formulations have been developed and employed for modeling phase transformations in other manufacturing processes and, particularly, in casting. The proposed model is mainly based on the combination and modification of some of these existing formulations, leading to a new overall model specifically dedicated to AM. The accuracy and suitability of the integrated model is enhanced, introducing new dedicated features. In fact the model is designed to deal with fast cooling and re-heating cycles typical of AM processes because: (a) it is able to consider incomplete transformations and varying initial content of phases and (b) it can take into account simultaneous transformations.The model is implemented in COMET, an in-house Finite Element (FE)-based framework for the solution of thermo-mechanical engineering problems. The validation of the microstructural model is performed by comparing the simulation results with the data available in the literature. The sensitivity of the model to the variation of material parameters is also discussed.

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