二元低熔点合金储热性能的研究

以低熔点合金Sn、Bi和Pb原料,制备了Sn-Bi、Sn-Pb和Bi-Pb共晶合金.采用XRD、DSC和激光热常数测试仪对产物结构和热物理性能进行了表征.结果表明,Sn-58Bi合金相变温度在136.9～149.1℃,相变潜热为40.84 J/g,比热容为0.17 J/(g K),热导率为16.2 W/(m K).在制备的合金中,储热能力大小依次为Sn-58Bi＞Sn-38Pb＞Bi-45Pb.     

Al-Cu-Mg-Zn合金相变储热材料热循环稳定性研究

采用XRD、DSC等对Al-Cu-Mg-Zn合金相变储热材料结构及热物理性能进行了表征.结果表明,Al-Cu-Mg-Zn共晶合金的相变温度和相变潜热分别为475.1℃和234.91 kJ/kg.通过热循环试验,对合金的热循环稳定性进行了研究.结果表明,随着热循环次数的增加,合金相变温度缓慢升高,合金相变潜热逐渐下降;经历1000次热循环后,合金相变储热材料仍具有较好的稳定性.     

Mg-15Ca-15Zn-6Cu相变储热材料的热循环稳定性

采用金相显微镜(OM)、X-射线衍射仪(XRD)、差热扫描仪(DSC)等分析手段对Mg-15Ca-15Zn-6Cu合金相变储热材料的组织结构与热物性参数进行了分析。通过反复熔化-凝固热循环试验,研究了该合金的热循环稳定性。结果表明,Mg-15Ca-15Zn-6Cu合金经历1 000次热循环后的相变温度和相变潜热分别为510.2℃和198.7J/g,与循环前的初始合金相比,相变温度提高了5.5%,相变潜热减小了5.56%,因此,表现出良好的热循环稳定性。     

Al-Si-Cu-Mg-Zn合金的高温相变储热性能研究

制备了20种基于Al-Si-Cu-Mg-Zn合金的高温相变储热材料,采用综合热分析技术研究其储热性能。结果表明,20种储热材料的相变温度处于440℃~650℃之间,均具有较大的相变潜热,大部分储热材料的相变潜热在200 J.g-1以上。Al-Si合金储热材料具有较高的单位质量储热量;Al-Cu-Zn合金储热材料具有较大的单位体积储热量;Mg、Zn能显著降低相变温度,具有较好的扩大储热温度范围作用。     

热处理和热循环对Ru-49Ta高温形状记忆合金马氏体相变行为的影响

用示差扫描热分析仪(DSC)、X射线衍射仪(XRD)和光学显微镜系统研究了热处理和热循环对Ru-49Ta高温形状记忆合金马氏体相变行为的影响。结果表明：Ru-49T8合金的Ms(马氏体相变开始温度)和Af(马氏体逆相变结束温度)分别为1065℃和1085℃，相变温度范围(Ms-Mf)为15℃，相变热滞和相变热比较小，分别为22℃和2J／g。热处理对Ru-49Ta合金马氏体相变行为影响不大，该合金的马氏体相稳定性良好，不存在时效效应，相变方式为孪生。热循环对Ru-49Ta合金马氏体相变温度和热滞影响不大，随热循环的进行，相变热有所减少。     

近强磁场作用对Sn-9Zn钎料合金组织性能的影响

运用X射线衍射仪、扫描电镜、显微硬度计等仪器设备,研究了0.8 T近强磁场作用对Sn-9Zn钎料合金组织和性能影响。研究结果表明：近强磁场可促进Sn-9Zn钎料合金显微组织显著细化,使熔化温度下降2℃,显微硬度提高11%。分析认为,由于外加磁场可促进Sn-9Zn钎料合金在特定晶面迅速结晶形核以及作用于液态钎料合金的的洛仑兹力对钎料作负功,从而促进Sn-9Zn钎料合金组织和性能的改变。     

Al-Si/Al2O3高温复合相变蓄热材料的研究

以Al-Si共晶合金为相变材料,白刚玉粉为陶瓷基体原料,用混合烧结法制备了Al-Si/Al2O3高温复合相变蓄热材料。通过对复合相变蓄热材料金相显微观察,DSC热分析,蓄热密度和导热系数的计算,结果表明,制备的高温复合相变蓄热材料具有良好的蓄热能力和快速蓄放热能力;对复合材料进行300次热循环试验后,其质量损失为0.84%,潜热值降低4.23%,相变温度略有升高,该复合材料的热稳定性良好。     

Mg-6Sn-3Al-1Zn合金热压缩行为研究

采用Gleeble3500热力模拟机对Mg-6Sn-3Al-1Zn合金在应变速率分别为0.001、0.01、0.1和1 s^-1,热力模拟机的温度分别为573、623、673和723 K进行了热压缩试验研究。结果表明,Mg-6Sn-3Al-1Zn合金在热变形行为中真应力与压缩温度成反比,但真应力与应变速率成正比。构建了合金的双曲正弦本构模型,揭示了Mg-6Sn-3Al-1Zn合金热加工时的变形机制,以及变形温度、应变速率和流变应力之间的关系。采用峰值应力与应变量分别为0.1、0.3和0.5时的应力,根据动态材料模型理论得到合金的热加工图。结果表明,该合金的最佳加工温度范围和应变速率范围分别为708～723 K和0.001～0.04 s^-1。     

电子束增材制造技术用Ti-Ni预合金粉末性能研究

采用DSC、SEM 和XRD等测试手段研究和分析了电子束增材制造（EBM）技术用53~106 μm Ti-Ni预合金粉末的性能及其随热处理温度和热循环次数的变化规律。结果表明：预合金粉末粒度呈正态分布,粉末内部填充及球形度良好,适于EBM打印使用;随热处理温度的升高预合金粉末相组成不发生变化但组织和成分变得均匀,内应力和位错被消除,晶粒尺寸长大,使得其550 oC热处理后加热和冷却过程由多步相变转变为单步相变,650 oC热处理后相变点开始保持稳定,而750 oC热处理后达到最佳微烧结状态;预合金粉末在750 oC烧结热循环和保温过程中相组成、单步相变行为和相变点均不发生变化,具有良好的热循环稳定性;底板及粉末层采用750 oC预热温度成功制备出表面状态良好的Ti-Ni合金实体样品。     

Ti100-xNix(x=40～70)形状记忆合金的Ni含量-时效工艺-相变行为关系图及其应用

采用示差扫描量热仪(DSC)建立了Ti_100-xNi_x(x=40～70)形状记忆合金的Ni含量-时效工艺-DSC曲线关系图、Ni含量-时效工艺-相变类型关系图、Ni含量-时效工艺-相变温度关系图、Ni含量-时效工艺-相变热滞关系图、Ni含量-时效工艺-相变潜热关系图。利用这些图能解决两类问题：当TiNi形状记忆合金的Ni含量、时效温度和时效时间已知时，可预测该合金的DSC曲线、相变类型、相变温度、相变热滞和相变潜热；当期望TiNi形状记忆合金具有某个DSC曲线、相变类型、相变温度、相变热滞或相变潜热时，可设计该合金的Ni含量、时效温度和时效时间。     

Properties of Cast Aluminium Alloys as Thermal Storage Materials

Abstract

This paper discusses the concept of using a cast aluminium alloy for thermal storage, utilising a phase change. The specific heat of both liquid and solid metal and the latent heat of melting of Al-Si, Al-Si-Mg and Al-Si-Cu alloys were measured using Differential Scanning Calorimetry (DSC) and by use of an Isothermal Copper-block Calorimeter (ICC). The thermal-cycling characteristics of these alloys, together with the change in the latent heat of Al-Si alloy were also measured during a holding period of 300 hr at elevated temperature. Taking into account the density of thermal storage, the thermal-cycling characteristics and cost, it is suggested that Al-Si alloy is probably the best choice when selecting a phase-change metal for thermal storage.     

MEASUREMENT AND APPLICATION OF PHYSICAL PARAMETERS IN UNSTEADY HEAT CONDUCTION

1.IntroductionPhysicalsimulatingandnumericcalculatingaremainrespectsofapplicationofcomputerinscienceandtechnology.Theaccuracyofsimulatingandcalculatingisaprincipleproblemforstudyanddiscussion.Obviously,toadoptareasonablemodelandmethodforcalculatingtemperaturefieldisaessentialpremisetopledgeaccuracyofcalculation.Oncethemodelforcalculationhasbeenestablished,itisadecisivefactortoselectthevaluesofphysicalparameters.Itisnecessarytoobtaintheparameterssuchasspecificheat,thermalconductivity,latenthea…     

基于NTC微珠状热敏电阻的稳态测量方法

稳态导热系数测量方法的原理和数学模型简单,但热源均温性要求高和测量时间长限制了稳态导热系数测量方法的实际应用。提出一种测量导热系数的新型微球法稳态热测量方法,建立对应的物理模型和试验方法。通过熔融共混法制备不同质量分数的石墨烯 石蜡复合相变材料,并采用微球法对不同质量分数的石墨烯 石蜡复合相变材料的导热系数进行测量。测量得到样品的导热系数分别为0.278 W/(m·K）(0%)、0.330 W/（m·K）(0.5%)、0.402 W/（m·K）(1%)、0.524 W/（m·K）(2%)、0.604 W/（m·K）(3%)、0.654 W/（m·K）(4%)和0.711 W/（m·K）(5%)。该方法具有微球体积小、热源均匀、测量快、样品制备简单等优点,可应用于实际工程中相变材料和液体的原位导热系数测量。     

冷却速度和合金成分对ZA合金结晶潜热的影响

采用差热分析方法（DTA）研究ZA合金结晶潜热的变化情况,发现ZA合金的结晶潜热随合金中铝含量的增加而增大,随冷却速度的增加而减小,结晶潜热与冷却速度之间答合幂指数关系。     

Temperature Variation in NiTi Shape Memory Alloy During Cyclic Phase Transition

Superelastic NiTi shape memory alloy (SMA) has high recoverable strain and outstanding damping capacity, and has been used as a damping material for many applications. When subjected to displacement-controlled cyclic deformation, the material exhibits distinctive temperature and stress oscillations due to the release of latent heat and hysteresis heat and the heat transfer with the ambient. In this paper, we establish a model to predict the temperature variation of NiTi SMA wire specimen under the cyclic phase transition by lumped heat transfer analysis. Closed-form solution on the evolution of the temperature is obtained. It is shown that, for all the test frequencies, steady-state cyclic thermal response of the specimen can be reached after a certain number of loading cycles in a transient stage, exhibiting a kind of ??thermal shake down.?? In the steady state, the temperature profile oscillates around a mean temperature plateau. We show that the temperature oscillation is mainly due to the release/absorption of latent heat during cyclic phase transition, while the mean temperature rise of the specimen is caused by the accumulation of the hysteretic heat of the phase transition. The model predictions agree well with the experimental results.     

不同熔体热处理工艺后Al-Cu-Ti合金的晶粒细化及力学性能改善

本文研究了添加细化剂和不同热处理工艺（过热处理和热速处理）对Al-Cu合金的改性。分析了Al-Cu-Ti合金的相组成、凝固微观组织和力学性能。此外,采用差示扫描量热法（DSC）研究了Al-Cu-Ti合金在不同熔体热处理工艺后的熔体结构转变行为。实验结果表明,热速处理极大地细化了Al-Cu-Ti合金晶粒,且力学性能得到有效改善。通过对热力学相变分析,发现Al-Cu-Ti合金经过热处理和热速处理后的熔化潜热随着界面能的增大而变小,从而在一定程度上细化了合金的微观组织。     

Determination of thermal conductivities of solid and liquid phases for rich-Sn compositions of Sn-Mg alloy

The variations of thermal conductivities of solid phases versus temperature for pure Sn and Sn-1 wt% Mg, Sn-2 wt% Mg, and Sn-6 wt% Mg binary alloys were measured with a radial heat flow apparatus. Thermal conductivity variations versus temperature for pure Sn and Sn-1 wt% Mg, Sn-2 wt% Mg, and Sn-6 wt% Mg binary alloys were found to be 60.60 ± 3.63, 61.99 ± 3.71, 68.29 ± 4.09, and 82.04 ± 4.92 W/Km, respectively. The thermal conductivity ratios of liquid phase to solid phase for pure Sn and eutectic Sn-2 wt% Mg alloy at their melting temperature were found to be 1.11 and 1.08, respectively, with a Bridgman type directional solidification apparatus. Thus the thermal conductivities of liquid phases for pure Sn and eutectic Sn-2 wt% Mg binary alloy at their melting temperature were evaluated to be 67.26 ± 4.03 and 73.75 ± 4.42 W/Km, respectively, by using the values of solid phase thermal conductivities and the thermal conductivity ratios of the liquid phase to the solid phase.     

Calculation of thermophysical properties of iron casting alloys

Abstract

A simple and easy calculation tool to determine thermophysical properties, such as density, heat capacity, liquidus and solidus temperature, thermal conductivity, latent heat, and volume contraction, of iron casting alloys based on equilibrium phase diagrams is introduced. It is well known that accurate thermophysical properties of iron casting alloys are necessary for a valid simulation of the casting process. While there are a number of thermophysical calculation programs, a specific knowledge of thermodynamics is required to operate them. The calculation method proposed in the present study does not require any special knowledge of thermodynamics, only information regarding the composition of the alloy. The proposed calculation tool is based on the CALPHAD approach for the modelling of multicomponent alloys using experimental published data. Comparison of calculated thermophysical properties for several conventional iron casting alloys with experimental results showed good agreement.     

无压烧结ZnAl/Fe基非晶复合材料的导热性能研究

采用无压烧结制备韧性Zn Al颗粒增强Fe基非晶复合材料,利用X射线衍射仪、扫描电镜、差热分析仪和激光闪射热导率测试仪分析了复合材料的结构、热稳定性及导热性能。结果表明:在过冷液相区内无压烧结可得到致密的Zn Al/Fe基非晶复合材料;Zn Al的引入没有影响Fe基非晶基体的本质;烧结过程中没有界面反应相生成;复合材料的热稳定性有所降低,但降低幅度不大;在298~423 K范围内,复合材料比Fe基非晶合金有更低的热传导系数,其热扩散系数随温度的升高变化不大,表明材料具有较好的保温性能。     

电子封装材料过共晶硅-铝合金的组织特征和热性能(英文)

采用快速凝固制粉技术和粉末热压烧结技术制备55%Si-Al,70%Si-Al和90%Si-Al3种过共晶含量的硅铝合金。结果表明:雾化沉积是制备过共晶硅铝合金的有效的快速凝固工艺,采用该工艺获得的快速凝固硅铝合金粉末的尺寸小于50μm。快速凝固的硅铝合金粉末经过550°C和700MPa热压后,获得3种不同成分合金试样的相对密度分别为99.4%,99.2%和94.4%。作为电子封装材料,3种试样的热导率、热膨胀系数和电导率都可以满足应用要求。55%Si-Al合金的热膨胀系数随温度的变化最剧烈,但是该合金具有较好的热导率。90%Si-Al合金的热膨胀系数较小,但是其热导率最差,小于100W/(m·K)。70%Si-Al合金具备热沉材料所应具备的优良的热导率和热膨胀系数的综合性能。