液-固和固-固相变时合金中高熔化熵相生长方式和形态随相变条件变化的机制和判据

Most of the second phases in multiphase alloys are the nonmetal and the intermetallic compound phases with high melting entropies. The morphology of high melting entropy phase (HSP) of the nonmetal and the intermetallic compound plays a decisive role in the mechanical property of the multiphase alloy. By the experimental measurement and computer simulation, this project aims to reveal the dependence of the growth characteristic and the morphology of HSP in the liquid-solid and solid-solid transformations on the phase transformation conditions (the solidification undercooling, the cooling rate and the temperature gradient, the solid-solid phase transformation temperature for heat treatment, etc.), and the dependence of the thermodynamics parameters related to the growth characteristic (the melting entropy, the liquid-solid interface energy, the phase-transformation entropy of the solid-solid transformation, the solid-solid interface energy) on the alloy composition. On this basis, by studying the relation among the growth modes, the thermodynamics parameters related to the growth characteristic and the phase transformation condition, the model will be established to determine the dependences of the growth mode and the morphology of HSP on the phase transformation parameters and alloy composition, and the theoretical criterion to judge the growth modes of HSP in the liquid-solid and solid-solid transformations and its morphology characteristic corresponding to different growth mode will be obtained, which will give the principle and data support for us to accurately predict and effectively control the growth mode and morphology of HSP during liquid-solid and solid-solid phase transformations in commercial production.

多相合金中的第二相大多是熔化熵高的非金属及金属间化合物相。高熔化熵非金属和金属间化合物第二相的形态对合金的力学性能起着决定性的作用。本项目通过实验测定和计算机模拟，获得液-固和固-固相变时合金中高熔化熵相生长特性和形态随相变条件（凝固时的过冷度、冷却速度和温度梯度；热处理固-固相变时的温度等）的变化规律及其相关热力学参数（熔化熵、液-固界面能、固-固相变熵、固-固界面能）随合金成分的变化规律；在此基础上，通过研究液-固和固-固相变时合金中高熔化熵相生长方式与相关热力学参数及相变参数之间的关系，建立高熔化熵相生长方式和形态随相变参数和合金成分变化的理论模型，获得液-固和固-固相变时合金中高熔化熵相生长方式转变的理论判据以及其以不同生长方式生长时的形态特征，为人们在工业生产中实现对液-固和固-固相变时合金中高熔化熵相生长方式和形态的准确预测和有效控制提供原理和数据支持。

合金中的第二相大多是熔化熵高的化合物相，其形态对合金的力学性能起着至关重要的作用。本项目通过对高熔化熵第二相生长特性随固溶和时效处理参数的变化规律；合金凝固中再辉速率与界面移动速率关系研究；非共晶成分合金受高熔化熵相支配的共晶凝固特性研究；合金凝固前后体积和密度变化研究；非晶合金相关理想玻璃转变温度等参数理论模型研究；熔体过冷处理和过热处理对高熔化熵相组织形态的影响研究；脉冲磁场处理和超声处理对高熔化熵相的相变行为的影响研究；分子动力学模拟熔体过热温处理对熔体形核生长过程影响的研究；金属熔体凝固过程中临界晶核尺寸随温度的变化规律；高熔化熵相生长方式和形态随相变条件变化等内容的研究，获得了高熔化熵相在多种工艺下的形态变化规律，揭示了合金在熔化与形核生长相变中的一些现象本质，并建立了相关数学模型。研究结果可为人们工业生产中实现对液-固和固-固相变时合金中高熔化熵相生长方式和形态的准确预测和有效控制提供原理和数据支持。

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