經由國科會補助的前期三年計畫中，本研究團隊發展新式相場法模擬多種材料微結構的組態與演化，成果非常豐碩。這包括受邀在國際會議發表特邀演講(keynote lecture)、撰寫專書章節、一系列近10篇的論文發表於固體力學頂尖期刊Journal of the Mechanics and Physics of Solids，金屬材料領域排名第一期刊Acta Materialia及應用物理領域領導期刊Applied Physics Letters。
儘管研究成果非常豐碩，本團隊所創立之新式相場法仍有兩大缺陷。首先本法只適用於模擬單相材料微結構。主要原因在於不同相之間的轉換應變(transformation strain)並不滿足「應變諧和條件」，導致在不同相中形成具不同尺度之微結構組態，造成數值模擬上極大困難。另外多晶智能材料為無數多具不同方位之單晶粒組成，材料自身內部即具有多種不同尺度，因此原所發展之相場法亦不適用此情形。但經由與美國華盛頓大學李江宇教授合作，開發出具雛型之雙尺度新式相場法，可用來模擬在不同相具不同尺度之微結構，初步結果已發表在2010 Applied Physics Letters 。
故本研究團隊在此提出一個為期三年的計畫，藉由發展雙尺度式相場法模擬在具不同尺度之智能材料微結構，研究項目包括 (1) 沃斯田鐵與麻田散鐵交界之模擬 (2) 應力或成份變化所引發之相變模擬 (3) 多晶材料雙尺度模擬。
Abstract: Smart materials are those which are able to sense and respond to the environment around them in a predictable and useful manner, and therefore, are often used in sensor and actuator applications. These materials often exploit various solid-to-solid phase transformations and other inherently nonlinear phenomenon, leading to intriguing and fascinating patterns of microstructure at extremely small scales. Performance optimization in these materials crucially depends on creating a microstructure with properties fitted to the application. Thus, there is a great need for the development of suitable materials models for microstructure simulations under various external fields.
Under the funding support by NSC in the past 3 years, we have successfully developed several novel phase filed models suitable for microstructure simulation in various smart materials. There are numerous research achievements, including one keynote lecture in an international conference, one book chapter, and around 10 SCI papers published in several prestigious SCI journals, including Journal of the Mechanics and Physics of Solids (the most prestigious journal in solid mechanics), Acta Materialia (the best journal in the category of metallurgy) and Applied Physics Letters (the leading journal in applied physics).
In spite of our fruitful research progress, there are two drawbacks in our present phase-field formulation. First, our model is limited to the case of materials with a single phase. The strain incompatibility between variants of different phases results in the different scales of microstructure formed in distinct phases. The second drawback of our framework is that it is unable to simulate material responses of a polycrystal due to multiple scales inherently inside a polycrystal. Fortunately, we have recently developed a two-scale phase field approach capable of capturing the feature of microstructure at different scales in distinct phases. This work is in collaboration with Professor Li at the University of Washington and the preliminary result has been recently published in 2010 Applied Physics Letters .
Thus, we propose a three-year investigation of developing various two-scale phase field models and use them to simulate microstructure in various cases. These include (1). Simulation of Austenite/Martenite Interfaces (b). Simulation of Phase Transition due to Variation of Stress or Composition (c). Simulation of Material Responses of a Polycrystal.
two-scale phase field method