单晶高温合金行业现状及其数值模拟应用综述

了解单晶高温合金的行业现状及其数值模拟应用,对于了解产品的市场动向以及提高产品的质量和研发效率具有现实意义.概述国内外单晶高温合金的行业现状及其数值模拟应用,重点总结我国单晶高温合金的研发状况、数值模拟技术在航空发动机用单晶高温合金制备工艺、性能评价等方面的应用,并提出改善我国单晶高温合金生长工艺与质量控制的努力方向.     

标准阴极电解加工整体叶轮数控编程

整体叶轮是火箭发动机、飞机发动机以及航空机载设备的重要零件之一.整体叶轮工作在高温、高压和高转速条件下,选用材料多为不锈钢、高温耐热合金和钛合金等难切削材料,再加上其为整体结构,并带有复杂型面的叶片,使得其制造起来非常困难,成为航空、航天制造技术中的关键.     

锡基合金硬度偏最小二乘回归预测模型

锡基合金具有摩擦系数小、硬度适中且韧性好等优点。其硬度由显微结构决定,因此,建立硬度与其微观结构间的定量相关模型,并分析其各相参数变化对硬度的影响,可以为研究新型合金和制定合金生产中的时效工艺提供参考和依据。基于锡基合金显微结构特点,通过提取合金金相特征参数,建立其硬度的关联预测模型。并通过实验数据分析了影响锡基合金硬度的因素及机理;对金相图做参数提取处理,用偏最小二乘回归分析对该参数进行硬度线性和非线性预测模型的构建。结果表明,该非线性偏最小二乘回归模型对锡基合金的硬度预测精度更高。     

大规模并行原子模拟在钛合金界面行为研究中的应用

界面对钛合金的力学性能有至关重要的影响。界面行为的原子模拟涉及的原子数目庞大,必须借助大规模并行计算。本研究组开发了大规模并行分子动力学程序,并将其应用于钛合金中不同种类界面行为的模拟研究。本文以钛铝金属间化合物中的孪晶界和 α 钛中的特殊大角晶界为例,介绍研究组在钛合金晶界行为的计算模拟方面的近期研究成果。所模拟的体系尺寸达到微米级,所需 CPU 核数几十至几百不等。研究发现,钛铝模拟晶胞沿伪孪晶方向剪切变形时,等静压力下可产生 L1₁ 结构的伪孪晶形核长大,而等静张力下剪切可产生真孪晶的形核长大,提出钛铝中一种新的孪晶长大机制。在 α 钛中,特定取向的两个晶粒所形成的晶界与位错发生相互作用,裂纹形核依赖于加载外力的取向而发生在晶界处或硬取向晶粒内,从而可能导致疲劳断裂行为与加载取向相关。这些结果有助于理解钛合金的塑性变形行为,并为更高尺度的模拟研究提供了原子尺度细节。     

发动机气路故障模拟试验台碰摩故障实验研究

航空发动机气路故障是重要且频发的发动机故障.其中,叶片-机匣碰摩故障是一种重要且频发的航空发动机气路故障.为了对其进行高效深入的研究,必须建立专门的气路故障模拟试验系统.基于静电监测技术设计了一种用于研究航空发动机气路故障的模拟试验台,实现了对航空发动机叶片-机匣碰摩故障模式的模拟.故障模拟实验结果表明:碰摩故障模拟实验感应信号具有周期性的特点,据此特征,可以在静电监测系统软件中实现对模拟碰摩故障的在线监测与识别.本研究验证了航空发动机气路故障模拟试验台模拟碰摩故障的有效性,为航空发动机故障监测和健康管理提供技术支撑.     

H∞回路成形方法在航空发动机控制中应用及验证

引入了基于频域理论的H∞回路成形方法对航空发动机进行控制器设计,有效地克服了类似于LQG的传统时域方法设计过程不透明的缺陷;为了提高控制器设计效率和准确性,在设计过程中,设计了一种能自动搜寻满足要求的权函数参数的方法,同时对传统的控制结构进行了改形,改善了控制器性能;为更充分对控制器性能进行验证,在设计的航空发动机数控系统快速原型化实时仿真平台上进行了仿真,证实了所设计的改型后的H∞回路成形控制器在航空发动机控制上所具有的良好的性能。     

航空发动机温度测量电路设计

为了提高航空发动机温度测量的精度和可靠性,给出了一种航空发动机温度测量电路的设计方法。该方法首先对航空发动机温度测量技术要求进行分析;进而设计了航空发动机低温、高温温度测量系统方案;最后采用模块化设计方法给出了关键的信号调理电路。该电路设计方法能满足航空发动机对不同温度环境测试的需求,有利于提高航空发动机工作温度测量系统的性能,具有一定的实际参考价值。     

高温电容位移传感器的设计与实验研究

为了精确测量航空发动机中的轴承座与外部机匣之间的相对变形量,应用高温合金、氧化铝陶瓷以及耐高温电缆等研制了可用于高温环境的特种电容位移传感器。将其安装于机匣的承力支板中,即可实现该相对变形量的测量。传感器采用双层屏蔽结构,并应用驱动电缆技术减小干扰信号的影响。本文首先对所设计的传感器进行了仿真分析,以验证其结构合理性,然后搭建实验平台完成了传感器的标定与性能测试,并进行了高温验证实验。实验结果表明,本文所研制的高温电容位移传感器能够在0~2.0 mm的范围内实现位移的精确测量,测量误差小于0.02 mm,并且能够在室温~500℃的温度范围内稳定工作,因而可以满足使用要求。     

油液磨粒传感器综合测试平台的设计研究

为了满足国内新研航空发动机磨损故障预测及健康管理研究要求,国内研究机构开展了油液在线式磨粒传感器的研究及测试。针对航空发动机油液磨粒传感器暂无准确量值、多参数组合的专业测试条件,提出了一种将精密直线运动控制与振动环境相结合的无介质测试平台技术方案,模拟发动机中润滑油流经传感器的运动状态并给出实验结果。实验结果表明该测试平台能够有效地应用于磨粒传感器的参数测试和性能探究,为航空发动机故障预测类传感器的技术研究提供了一种新的测试验证手段。     

基于GPU加速的定向凝固相场模拟计算研究

相场法作为一种极具优势的微观组织数值模拟方法,已经在凝固微观组织演化机制的研究中得到了广泛应用。然而无论是从计算尺度还是微观组织演化时间上考虑,相场模拟计算量均非常大,对计算机有着非常高的要求。相对于传统的中央处理器(CPU)计算,图形处理器(GPU)计算是最近发展的一种高效计算手段。提出了一种基于GPU加速的定向凝固相场模拟计算策略,实现了大尺度条件下的定向凝固界面形态演化的加速计算。计算结果表明,对于单个计算机,GPU计算与CPU计算的加速比可以高达30余倍。GPU加速将为相场模拟的发展及应用带来新的契机。     

First-principles-based statistical thermodynamic study of atomic interactions and phase stability in Ni-rich Ni-W alloys

Atomic interactions and phase stability in Ni-rich Ni-W alloys have been investigated by using first-principles methods and statistical thermodynamic simulations. First-principles methods have been employed to explore lattice expansion, enthalpies of formation, atomic interactions, and ordering energies of ordered as well as random structures in Ni-rich Ni-W alloys with consideration of the corresponding temperature-dependent magnetic states. It is found that atomic interactions in Ni-rich Ni-W alloys depend on alloy composition, atomic volume, and magnetic state. Nevertheless, the magnetic state of Ni greatly affects the formation enthalpies, which leads to a diverse phase separation behavior at finite temperature in Ni-rich Ni-W alloys. By using atomic interactions that reproduce the ordering energies obtained in the direct total energy calculations, our statistical thermodynamic simulations of chemical short-range order results show that fcc-based ordered D1${}_{\mathrm{a}}$, D0₂₂, and Pt${}_2$Mo phases can be observed in Ni-20 at.% W, Ni-25 at.% W, and Ni-33 at.% W alloys, respectively. Moreover, the short-range order diffuse intensity and atomic stacking for aforementioned ordered phases have been analyzed, the order–disorder transition behaviors have been also investigated in detail for the Ni-rich Ni-W alloys up to 35 at.% W with comparison of current experimental results. Both magnetic state and alloy composition have the potential to induce the formation of distinct ordered phases, offering promising avenues for designing Ni-based alloys. The methodologies we used in this study can be applied to investigate the atomic interactions as well as phase stability in other alloy systems.     

Interdiffusion and atomic mobilities in bcc V–X (X = Mn,Sn and Ni) alloys: Measurement and modeling

Totally 8 diffusion couples were prepared and the composition-dependent interdiffusion coefficients in bcc V–Mn, V–Sn and V–Ni alloys were measured between 1323 and 1503 K by means of Sauer-Freise method coupled with electronic probe microanalysis (EPMA) technique. The errors of the interdiffusion coefficients were computed by error propagation method. Based on the measured interdiffusivities and thermodynamic parameters from the literature, the atomic mobilities of bcc V–X (X = Mn, Sn and Ni) alloys were obtained by using the CALTPP (CALculation of ThermoPhysical Properties) program with the features of high efficiency and accuracy in the framework of CALPHAD (CALculation of PHAse Diagram) approach. For each system, the presently obtained atomic mobilities were validated by good agreement between the calculated interdiffusivities and the measured ones. The model-predicted concentration profiles in this work are consistent with the experimental ones. This work contributes to the establishment of the atomic mobility database containing V element and the key input for microstructure simulations in V-based alloys.     

Robust miniaturized amplification unit for piezoelectric actuators: comparison of single crystal silicon and superelastic nickel titanium as membrane materials

In this work, amplification units made of robust metallic nickel titanium (NiTi) and single crystal silicon are compared and evaluated for the application in miniaturized piezoelectric actuators for flow control purposes. The amplification mechanism with a sliced membrane structure is based on a mechanical lever in order to amplify the low piezoelectrically induced deformation. Therefore, an enhanced output stroke can be provided up to high frequencies. The different membrane fabrication processes using laser ablation for the NiTi alloy and deep reactive ion etching for the silicon substrate, as well as the results of finite element simulations and experimental measurements are reported. An amplification factor of 9 has been achieved for an optimized load transmission point position. The dynamic response shows a quality factor of 25 and 494 at the first fundamental mode for NiTi and silicon membranes, respectively. Compared to silicon, NiTi shows enhanced properties against failure and facilitates the integration process.     

Mobilities and diffusivities in fcc Co–X (X=Ag,Au, Cu,Pd and Pt) alloys

The mobilities and diffusivities in fcc Co–X (X=Ag, Au, Cu, Pd and Pt) alloys have been critically assessed by the CALPHAD method, based on the reported experimental data and published thermodynamic parameters. The atomic mobilities are expressed as functions of temperature and compositions in the CALPHAD format. Comprehensive comparisons between the calculated and measured diffusivities, such as self-diffusivities, impurity diffusivities, intrinsic diffusivities, and interdiffusivities, are made, where the proposed mobility parameters for Ag, Au, Co, Cu, Pd and Pt enable most of the experimental values to be reproduced. The effect of magnetic ordering on diffusion in fcc Co–Pd and Co–Pt alloys is discussed. This work contributes to the establishment of a Co mobility database, which can aid the computational study of microstructure evolution in Co-based alloys at high temperatures.     

钛合金常规加工的有限元模拟

为验证不同Johnson-Cook本构参数对钛合金切削仿真的可靠性,基于AdvantEdge建立钛合金的二维正交切削仿真模型。然后将查找文献得到的不同钛合金本构参数与实验进行对比,分析切削过程中切削力和最高切削温度的误差。发现AdvantEdge软件的自定义Johnson-Cook本构在钛合金的切削仿真过程中,不同本构参数存在相对误差过大的问题,需要后续调节参数减小与实验的误差。     

Alloy composition and process design based on thermodynamic and kinetic simulation: The case of medium Mn steel

This paper presents a design method for alloy materials that can be applied to medium Mn steel containing Al and/or Si. By using thermodynamic calculations based on CALPHAD, a wide range of alloy composition spaces were systematically studied, and the relationship between retained austenite fraction and its stability with intercritical annealing temperature was investigated. Alloys that meet the Process Window (PW) were screened and their various characteristics of alloy elements within the process window were determined. Additionally, the study performs three different kinetic simulations of austenite growth and solute partitioning during isothermal annealing on alloys that meet PW. The prediction of the model is verified by comparing with the experimental data in the literature. The results show that the remote model is more suitable for the actual production of low temperature isothermal intercritical annealing. Therefore, the method provided in this work makes a guiding contribution to alloy development, which can determine the alloy composition and heat treatment process satisfying PW and optimize the overall properties.     

Atomic mobilities and diffusion characteristics for fcc Cu-Ag-Au alloys

CALPHAD kinetics has evolved to be a well-established discipline, which allows complex non-equilibrium processes to be fully explored. Such a success relies on the use of Redlich-Kister polynomials to describe atomic mobilities, with the effect of temperature, composition, magnetic ordering and chemical ordering sufficiently taken into consideration. There is thus an increasing demand to construct high-quality atomic mobility databases for alloys of interest. Based on the CALPHAD framework, the atomic mobilities in fcc Cu-Ag-Au alloys are reported in this work, the results of which can provide fruitful information on alloy design.     

NEG thin films for under controlled atmosphere MEMS packaging

Non-evaporable getter (NEG) thin films for residual gases control in micro-electro-mechanical systems (MEMS) cavities after sealing are considered. For this study, several getters are deposited and analyzed in terms of sorption performances, microstructure and activation mechanism. Compared to single layer evaporated titanium reference, the addition of a chromium sub-layer is shown to decrease the activation temperature of the NEG. Moreover, when activated under 0.2 mbar of N₂, nitrogen diffusion in the titanium layer is enhanced by sub-layer addition. Effective pumping of nitrogen is monitored by residual gas analysis (RGA). Transmission electron microscopy investigation of as-deposited thin film getters reveals Ti layer microstructure modification due to platinum sub-layer addition. Furthermore, activation under nitrogen atmosphere is shown to induce microstructure modifications for both getters. X-ray photoelectron spectroscopy (XPS) and depth profiling monitoring of NEG activation under high vacuum conditions (10⁻⁸ mbar) shows the dissolution of the NEG surface oxide in the getter bulk, along with the formation of carbide and nitride compounds. These results are in good agreement with already published results on getter alloys.