Al-1.5Cu-3Zn合金的溶质分凝因数的实验和模型研究

采用液态金属冷却技术淬火得到了温度梯度在80K／cm时Al-1．5Cu-3Zn合金的固液界面,使用光学显微镜观察了界面形貌,发现在生长速度为0．1和7．1pμm／s时试样分别为胞状生长界面和枝晶生长界面。用SEM和EDS测量了溶质分配,计算出了A1-1．5Cu-3Zn合金中Cu和Zn的平衡分凝因数为0．31和0．58。采用活度模型和浓度模型进一步计算了平衡分凝因数,发现两个模型计算出的Cu和Zn的平衡分凝因数一致,并讨论了模型计算值和试验值之间的差异。     

凝固路径对Al-4.5%Cu合金显微偏析参数影响的数值模拟

通过对Al-4.5%Cu合金铸锭显微偏析形成的数值模拟,研究了凝固路径对凝固后铸锭不同位置处显微偏析参数的影响.在显微偏析模型中考虑了树枝晶粗化、固相溶质逆扩散、枝晶尖端过冷、随温度变化的溶质扩散系数等影响显微偏析形成的动力学因素.数值方法中采用变网格技术跟踪移动界面,通过迭代求解溶质扩散方程和溶质守恒方程计算显微偏析参数.结果表明,对于Al-Cu合金,固相扩散主要由溶质扩散速率控制,而非局部凝固时间.显微偏析参数不仅取决于局部凝固时间,还要考虑凝固路径的影响.     

三元合金单相凝固路径的统一解析模型

基于合金枝晶凝固微观偏析统一模型,导出一种新的描述三元合金单相凝固路径的解析模型.该模型具有统一性,不仅可涵盖平衡、非平衡和准平衡3种极限凝固路径模式,而且可考虑任意凝固相的反扩散、冷速和枝晶几何形貌等因素的影响.通过对Al-1.0Cu-6.3Mg,Al-1.49Si-0.64Mg和Al-1.49Si-2.90Mg(质...     

枝晶形貌假设对AlCuSi合金凝固路径计算的影响

基于相图计算方法,耦合微观凝固模型,计算了Al-Cu-Si合金的凝固路径,研究了不同枝晶形貌假设条件下合金凝固路径的区别,并获得了温度与固相体积分数变化的定量关系。计算结果表明:Al-4.61Cu-0.92Si合金在Lever模型条件下的凝固路径为:L→(L+α),而在球形、圆柱、等轴晶、内圆柱、平板、内球等枝晶形貌假设下的凝固路径为:L→(L+α)→(L+α+θ)→(L+α+θ+Si)。枝晶形貌假设对合金凝固路径计算结果的影响较大,球状与圆柱状枝晶形貌假设条件下的计算结果与Lever模型比较接近,而平板、内球与内圆柱枝晶形貌假设条件下的计算结果更加接近Scheil模型。     

合金凝固的二相流数值模拟

本文介绍了合金凝固传输过程中的二相流数学模型，该模型描述了固－液界面的传输现象和液相对流对宏观偏析的影响，并考虑了生核过程，热和溶质的过效应，及固相颗粒的宏观运动，从而把观传输过程和微观结构结合起来；采用该模型，对Ａｌ－４％Ｃｕ等轴晶合金的凝固进行了完整的数值模拟。     

凝固路径对Al-4.5%Cu合金共晶相体积分数影响的数值模拟研究

通过Al-4.5％Cu合金铸锭显微偏析形成的数值模拟，研究了凝固路径对凝固后铸锭不同位置处共晶相体积分数的影响。在显微偏析模型中考虑了树枝晶粗化、固相溶质逆扩散、枝晶尖端过冷、随温度变化的溶质扩散系数等影响显微偏析形成的动力学因素。数值方法中采用变网格技术跟踪移动界面，通过迭代求解溶质扩散方程和溶质守恒方程计算显微偏析参数。结果表明，不能仅靠局部凝固时间来分析共晶相体积分数的变化，还要考虑凝固路径的影响。     

Al-4%Cu合金铸件凝固过程温度场的数值模拟

利用ANSYS软件对Al-4%Cu合金铸件凝固过程中的温度场进行了模拟,得到了铸件各点温度随时间变化的规律。模拟结果形象地反映了铸造过程中铸造系统温度的变化过程。进行了温度场的实际测试,结果表明:通过建立合理的模型和设置合理的边界条件,ANSYS模拟结果与实测结果符合较好。     

Al-Si合金凝固组织的数值模拟及预测

建立有限元(Finite Element)和元胞自动机法(Cellular Automaton)相结合的宏微观耦合的CA-FE模型,模拟不同工艺条件下Al-Si合金的凝固组织,进行了热态验证实验.结果表明,模拟结果与实验结果基本吻合,能够较为准确地反映出等轴晶和柱状晶的分布位置、比例和大小;随着浇注温度的提高,铸件凝固组织中柱状晶比例逐渐增大,且晶粒明显变得粗大;铸锭的凝固组织主要受铸模本身冷却能力的控制,而受外界的冷却强度影响不大,随着铸模厚度的增大,凝固组织中柱状晶比例逐渐增大.     

Effects of cooling rate and initial composition on the solidification path and microstructure of Al-Cu-Si alloys

The influences of cooling rate and initial composition on solidification path, microstructure and hardness of Al-Cu-Si alloys were investigated. The results indicate that the solidification paths of alloys Al-3.7Cu-6.5Si, Al-5.2Cu-2.6Si and Al-15.1Cu-6.2Si were (L + α-Al)→(L + α-Al+ β-Si)→(L + α-Al+ β-Si+ θ-Al₂Cu), and the solidification paths of alloys Al-4.6Cu-0.9Si, Al-24.2Cu-3.9Si and Al-26.9Cu-2.1Si were (L + α-Al)→(L + α-Al+ θ-Al₂Cu)→(L + α-Al+ β-Si+ θ-Al₂Cu). Furthermore, it is found that the further the initial compositions from the binary eutectic trough and the slower the cooling rate was, the second dendrite arm spacing was larger and the volume percent of phase θ-Al₂Cu was fewer, and then influence the hardness. There were three kinds of (α-Al+ θ-Al₂Cu) binary eutectic, two kinds of (α-Al+ β-Si+ θ-Al₂Cu) ternary eutectic and one kind of (α-Al+ β-Si) binary eutectic morphologies existed in the solidification specimens.     

Calculation of Cu-rich part of Cu-Ni-Si phase diagram

The thermodynamic calculation of phase equilibria in the Cu-Ni-Si alloy system was carried out using the CALPHAD method. The calculations show that there are three two-phase areas and two three-phase areas in the Cu-rich parts of the isothermal section of the phase diagram at 300-600 ℃ , and the three two-phase areas are FCC-Al（Cu-rich）＋γ-Ni5Si2, FCC-Al（Cu-rich）＋δ-Ni2Si and FCC-Al（Cu-rich）＋ε-Ni3Si2, two three-phase areas are FCC-Al（Cu-rich）＋）,-Ni5Si2＋δ-Ni2Si and FCC-Al（Cu-rich）＋δ-Ni2Si＋e-Ni3Si2. For this reason, an alloy located in the Cu-rich portion may precipitate γ-Ni5Si2, δ-Ni2Si or ε-Ni3Si2; the proportion of each phase depends on the alloy composition and aging temperature. The transmission electron microscope analysis of the Cu-3.2Ni-0.75Si alloy indicates that the precipitates are mainly δ-Ni2Si with only a few γ-NisSi2 phase particles, which agrees well with the thermodynamic calculations of phase equilibria.     

液态金属快速凝固过程的PFM模型

近年来发展起来的PFM模型根据"溶质捕捉"和"溶质牵引"两种机制对金属及合金快速凝固过程进行数学描述及模拟, 较好地反映了金属凝固的物理本质. 介绍了PFM模型发展过程、研究现状及理论模型, 并对发展前景进行了展望.     

Ce-La-O体系相图热力学及应用(英文)

采用实验测量和热力学计算相结合的方法,系统研究Ce-La-O体系相图热力学和Ce-La合金的氧化反应过程。制备一系列不同成分的CeO2-LaO1.5混合物并对其进行X-射线衍射分析,获得了LaO1.5与CeO2在1273K时的相互固溶度;利用该研究测量以及文献报道的实验数据,优化了CeO2-LaO1.5体系相图;结合已有的Ce-O和La-O体系热力学描述,计算了Ce-La-O体系状态图并解释了Ce-La合金的氧化反应过程,发现只要La含量不超过80%,Ce-La合金被氧化后均形成CeO2为基的固溶体。     

相场法凝固组织模拟的研究进展

阐述了相场法是一种用于模拟凝固微观组织的有效方法 ,是目前国内外的研究热点 ;论述了相场法模拟凝固微观组织的原理和国内外的研究现状 ,并指出进一步研究的方向。     

Subsolidus binary phase diagram of C10Zn-C18Zn of thermotropic phase transitions materials

The thermotropic phase transitions layer compound in the perovskite type (n-C10H21NH3)2ZnCl4 and (n-C18H37NH3)2ZnCl4 were synthesized and, at the same time, a series of mixtures C10Zn/C18Zn were prepared. The experimental binary phase diagram of C10Zn/C18Zn was established by means of differential scanning calorimetry (DSC) and X-ray diffraction. In the phase diagram, compound (n-C10H21NH3)(n-C21H37NH3)ZnCl4 and two eutectoid invariants were observed; two eutectoid temperatures are about 53℃ and 58℃. Contrasting with other similar systems, there are three noticeable solid solution ranges at the left and right boundary and middle of the phase diagram.     

无铅锡基钎料合金设计和合金相图及其计算

阐述了无铅钎料合金设计的原则, 讨论了合金相图及其计算在无铅锡基钎料合金设计中的作用. 利用相图计算技术筛选了可能代替Pb-Sn共晶钎料合金的Sn-Zn-In三元(x(Zn)＜0.11, x(In)=0.10～0.14)和Sn-Zn-In-Ag四元(x(Sn)=0.800, x(In)=0.090, x(Zn)=0.075, x(Ag)＜0.049)无铅锡基钎料合金. 初步讨论了用相图计算技术在富Sn四元Sn-Zn-In-Ag无铅钎料合金基础上, 添加Bi, Sb等低熔点金属和微量Ce, La等稀土元素以降低贵金属In和Ag的含量, 进一步提高无铅锡基多元合金钎料的综合性能和性能价格比.     

Numerical simulation of solidification morphologies of Cu-0.6Cr casting alloy using modified cellular automaton model

The purpose of this study is to predict the morphologies in the solidification process for Cu-0.6Cr (mass fraction, %) alloy by vacuum continuous casting (VCC) and verify its accuracy by the observed experimental results. In numerical simulation aspect, finite difference (FD) method and modified cellular automaton (MCA) model were used to simulate the macro-temperature field, micro-concentration field, nucleation and grain growth of Cu-0.6Cr alloy using real data from actual casting operations. From the observed casting experiment, the preliminary grain morphologies are the directional columnar grains by the VCC process. The solidification morphologies by MCAFD model are in agreement with the result of actual casting experiment well.