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相变区控制冷却速度对ER70S-6钢线材组织性能的影响 被引量:7
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作者 丁华 王丽 +1 位作者 刘雅政 张立芬 《特殊钢》 北大核心 2001年第6期18-20,共3页
通过热模拟机Gleeble 15 0 0对控制冷却过程的模拟 ,研究了相变区冷却速度 (即冷速 )对ER70S 6焊线钢的组织结构、铁素体量、铁素体平均晶粒尺寸和力学性能的影响。试验结果表明 ,在相变区冷速小于 1℃ s时 ,钢的塑性较好。
关键词 ER70S-6钢 线材 性能 组织 控制冷却 焊丝 相变冷却速度
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氧化铝相变动力学 被引量:2
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作者 杨国庆 严东生 《硅酸盐学报》 EI CAS 1966年第1期1-11,共11页
氧化铝在高温下的相变历程相当复杂,是近年来研究得较多的一个问题,但是对相变动力学却还很少涉及。本文从测定试样在恒温处理过程中的比重变化,研究了氧化铝的相变动力学。试样用火焰雾化法淬冷制得,含有约 2%TiO_2作为添加物,它的主... 氧化铝在高温下的相变历程相当复杂,是近年来研究得较多的一个问题,但是对相变动力学却还很少涉及。本文从测定试样在恒温处理过程中的比重变化,研究了氧化铝的相变动力学。试样用火焰雾化法淬冷制得,含有约 2%TiO_2作为添加物,它的主要相组成是γ-Al_2O_3,并含有5~8%的a-Al_2O_3。X-射线分析证实这种α-Al_2O_3的相变历程是:γ-Al_2O_3→δ-Al_2O_3→α-Al_2O_3,其中δ→α-是较慢的过程。文中讨论了相变的机构,并假设从δ-Al_2O_3至α-Al_2O_3的相变速度决定于相界面面积,可用下式表示之: dy/dt=k(1-y)y^(2/3)式中y是试样中α-Al_2O_3的分数,t是时间,k是比速度常数。实验结果证实上式是适用的,从而计算了在1098~1190℃范围内的k值,并求得比速度常数k和温度的关系是:k=Aexp(-153,000/RT)。153千卡/克分子的能量应看作是α-Al_2O_3在δ-Al_2O_3母相中的生长活化能,而铝离子的体积扩散可能是过程的控制因素。文中还讨论了Clark和 White的实验结果,并提出了可能的解释。 展开更多
关键词 相变动力学 严东生 氧化铝 铝化合物 晶体生长 粉末样品 晶核 等温相变 射线衍射 相变速度 成核 比重变化 控制因素 晶粒长大 晶粒生长 Al
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自支撑相变压裂技术中相变热对裂缝温度的影响
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作者 张楠林 刘福深 +5 位作者 姜亮亮 罗志锋 琚宜文 刘平礼 赵立强 裴宇昕 《石油勘探与开发》 EI CAS 2024年第6期1374-1383,共10页
采用差示扫描量热法测试了相变流体热通量曲线,以此建立反映相变转化率与温度、时间关系的反应动力学模型,进而构建了考虑相变热的裂缝和岩体温度场模型,采用前人建立的温度场模型验证了本模型的可靠性,利用新模型研究了不同注入参数、... 采用差示扫描量热法测试了相变流体热通量曲线,以此建立反映相变转化率与温度、时间关系的反应动力学模型,进而构建了考虑相变热的裂缝和岩体温度场模型,采用前人建立的温度场模型验证了本模型的可靠性,利用新模型研究了不同注入参数、相变压裂液性能参数对裂缝和岩体温度变化的影响规律。研究表明:缝内温度在不同位置、不同时间受注入冷流体的冷却效应和相变过程中的放热效应交替主导;压裂液注入初期,缝内温度较高、相变速度较快,相变放热对储层岩石温度影响较大;注入后期,缝内温度降低,相变放热速度减慢、压裂液对储层岩石的冷却效应增强。相变热对裂缝温度的影响较大,与不考虑相变热相比,当考虑相变热时,注液结束时缝内温度均有不同程度上升,当相变热由20J/g上升至60J/g时,缝内温度上升最大值由2.1℃升至6.2℃。相变热和相变流体(PF)体积分数与裂缝温度变化呈正相关,比热容则与温度变化呈负相关。随着注入时间的增加,缝口温度、相变速度逐渐降低,最大相变速度和最大温度差值位置逐渐从缝口转移到距缝口约10 m处。 展开更多
关键词 自支撑相变压裂 原位自生支撑剂 反应动力学 相变 相变速度 裂缝温度
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Influence of cooling rate on phase transformation and microstructure of Ti-50.9%Ni shape memory alloy 被引量:4
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作者 张艳秋 江树勇 +1 位作者 赵亚楠 唐明 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2012年第11期2685-2690,共6页
Heat treatment of Ti-50.9%Ni (mole fraction) alloy was studied by differential scanning calorimetry, X-ray diffraction, scanning electron microscopey and energy dispersive X-ray analysis to investigate the influence... Heat treatment of Ti-50.9%Ni (mole fraction) alloy was studied by differential scanning calorimetry, X-ray diffraction, scanning electron microscopey and energy dispersive X-ray analysis to investigate the influence of cooling rate on transformation behavior and microstructures of NiTi shape memory alloy. The experimental results show that three-stage phase transformation can be induced at a very low cooling rate such as cooling in furnace. The cooling rate also has a great influence on the phase transformation temperatures. Both martensitic start transformation temperature (Ms) and martensitic finish transformation temperature (Mf) decrease with the decrease of the cooling rate, and decreasing the cooling rate contributes to enhancing the M→A austenite transformation temperature. The phase transformation hysteresis (Af-Mf) increases with the decrease of the cooling rate. Heat treatment is unable to eliminate the textures formed in hot working of NiTi sample, but can weaken the intensity of them. The cooling rate has little influence on the grain size. 展开更多
关键词 NiTi alloy shape memory alloy phase transformation cooling rate martensitic transformation temperature austenite transformation temperature
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Effect of growth rate and diameter on microstructure and hardness of directionally solidified Ti-46Al-8Nb alloy 被引量:2
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作者 刘国怀 李新中 +6 位作者 张元 陈瑞润 苏彦庆 郭景杰 傅恒志 王昭东 王国栋 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第12期4044-4052,共9页
Bridgman-type directional solidification experiments were conducted for Ti-46Al-8Nb (mole fraction, %) alloy. The effects of the growth rate and the diameter on the microstructure, phase transition and hardness of t... Bridgman-type directional solidification experiments were conducted for Ti-46Al-8Nb (mole fraction, %) alloy. The effects of the growth rate and the diameter on the microstructure, phase transition and hardness of the alloy were investigated. The results show that with the increase of the growth rate and the decrease of the diameter, the fullyβphase solidification changes to the peritectic solidification, and the final microstructure is composed of theα2/γlamellar structure and a multiphase microstructure (B2 phase,α2/γlamellar structure) respectively, which can be attributed to the solute enrichment resulting from the decreasing diffusion and convection ability. The occurrence of peritectic reaction at high growth rate promotes the solute segregation heavily and the coarse lamellar spacing in Al-and Nb-rich region, which greatly decreases the hardness values and leads to the discontinuity of the hardness curves with the increase of the growth rate. Comparatively, the Ti-46Al-8Nb alloy has lower hardness values than the other applied TiAl-based alloys in previous studies. 展开更多
关键词 TiAl alloy directional solidification growth rate DIAMETER phase transition
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Numerical analysis of 3D spot continual induction hardening on curved surface of AISI 1045 steel 被引量:1
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作者 高恺 汪舟 +1 位作者 秦训鹏 朱生霄 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第5期1152-1162,共11页
In order to investigate and predict the material properties of curved surface AISI 1045 steel component during spot continual induction hardening(SCIH),a 3D model for curved surface workpieces which coupled electromag... In order to investigate and predict the material properties of curved surface AISI 1045 steel component during spot continual induction hardening(SCIH),a 3D model for curved surface workpieces which coupled electromagnetic,temperature and phase transformation fields was built by finite element software ANSYS.A small size inductor and magnetizer were used in this model,which can move along the top surface of workpiece flexibly.The effect of inductor moving velocity and workpiece radius on temperature field was analyzed and the heating delay phenomenon was found through comparing the simulated results.The temperature field results indicate that the heating delay phenomenon is more obvious under high inductor moving velocity condition.This trend becomes more obvious if the workpiece radius becomes larger.The predictions of microstructure and micro-hardness distribution were also carried out via this model.The predicted results show that the inductor moving velocity is the dominated factor for the distribution of 100% martensite region and phase transformation region.The influencing factor of workpiece radius on 100% martensite region and phase transformation region distribution is obvious under relatively high inductor moving velocity but inconspicuous under relatively low inductor moving velocity. 展开更多
关键词 spot continual induction hardening curved surface heating delay phenomenon
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Evolution of V-containing phases during preparation of Al-based Al−V master alloys 被引量:1
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作者 Yi MENG Yue YANG +4 位作者 Cen LI Lei-gang CAO Zhi-hao ZHAO Qing-feng ZHU Jian-zhong CUI 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2022年第7期2110-2124,共15页
Al-based Al−V master alloys were prepared by both the stepwise heating melting experiment and stepwise melting cooling experiment with rapid solidification to investigate the transformation of V-containing phases whic... Al-based Al−V master alloys were prepared by both the stepwise heating melting experiment and stepwise melting cooling experiment with rapid solidification to investigate the transformation of V-containing phases which gave different effects on microstructures and properties of commercial Al alloys and Ti alloys,as both melting and solidification processes affect the evolution of V-containing phases largely.The results showed that the raw Al−50wt.%V alloy consisted of needle-like Al_(3)V phase and Al8V5 phase(matrix),while petal-like Al_(3)V,needle-like Al_(7)V and plate-like Al_(10)V phase were present in the Al−V master alloys.The metastable Al_(7)V phase was evolved from Al_(3)V phase and then evolved into Al_(10)V phase during melting process.The number of Al_(10)V phase increased with the decrease of temperature in the range of 800−1000℃.Petal-like Al_(3)V phases could be transformed from Al_(8)V_(5) phase,pre-precipitated from Al−V molten liquid during melting process and precipitated directly during rapid solidification,respectively. 展开更多
关键词 Al-based Al−V master alloy phase transformation vanadium-containing phase rapid solidification pouring temperature
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Development of aluminum rheo-extrusion process using semi-solid slurry at low solid fraction 被引量:2
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作者 T.RATTANOCHAIKUL S.JANUDOM +1 位作者 N.MEMONGKOL J.WANNASIN 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2010年第9期1763-1768,共6页
An aluminum extrusion process is mainly used to fabricate long tubes, beams and rods for various applications. However, this process has a high production cost due to the need for investment of high-pressure machinery... An aluminum extrusion process is mainly used to fabricate long tubes, beams and rods for various applications. However, this process has a high production cost due to the need for investment of high-pressure machinery. The objective of this work is to develop a new semi-solid extrusion process using semi-solid slurry at low solid fractions. A laboratory extrusion system was used to fabricate aluminum rods with the diameter of 12 ram. The semi-solid metal process used in this study was the gas induced semi-solid (GISS) technique. To study the feasibility of the GISS extrusion process, the effects of extrusion parameters such as plunger speed and solid fi-action on the extrudability, microstructure, and mechanical properties of extruded samples were investigated. The results show that the plunger speed and solid fraction of the semi-solid metal need to be carefully controlled to produce complete extruded parts. 展开更多
关键词 aluminum alloys EXTRUSION semi-solid metal rheo-extrusion gas induced semi-solid (GISS)
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Transformation mechanism and mechanical properties of commercially pure titanium 被引量:7
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作者 徐春 朱文峰 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2010年第11期2162-2167,共6页
In order to establish the rolling process parameters of grade-2 commercially pure titanium (CP-Ti), it is necessary to understand the transformation mechanism and mechanical properties of this material. The β→α t... In order to establish the rolling process parameters of grade-2 commercially pure titanium (CP-Ti), it is necessary to understand the transformation mechanism and mechanical properties of this material. The β→α transformation kinetics of the grade-2 CP-Ti during continuous cooling was measured and its hot compression behavior was investigated using Gleeble-1500 thermal mechanical simulator. Dynamic CCT diagram confirms that cooling rate has an obvious effect on the start and finishing transformation and microstructures at room temperature. The critical cooling rate for γ-phase transforms to a phase is about 15℃/s. When the cooling rate is higher than 15 ℃/s, some β phases with fine granular shape remain residually into plate-like structure. The plate-like a phase forms at cooling rate lower than 2 ℃/s, serrate a phase forms at medium cooling rates, about 5-15℃/s. The flow stress behavior of grade-2 CP-Ti was investigated in a temperature range of 700-900℃ and strain rate of 3.6-40 mm/min. The results show that dynamic recrystallization, dynamic recovery and work-hardening obviously occur during hot deformation. Constitutive equation of grade-2 CP-Ti was established by analyzing the relationship of the deformation temperature, strain rate, deformation degree and deformation resistance. 展开更多
关键词 commercially pure titanium phase transition mechanical properties flow stress
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Lump Solutions of Kadomtsev-Petviashvili I Equation in Non-uniform Media 被引量:1
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作者 朱晓明 张大军 陈登远 《Communications in Theoretical Physics》 SCIE CAS CSCD 2011年第1期13-19,共7页
N-lump solutions of the Kadomtsev-Petviashvili I equation in non-uniform media are derived through the inverse scattering transform. The obtained solutions describe lump waves with time-dependent amplitudes and veloci... N-lump solutions of the Kadomtsev-Petviashvili I equation in non-uniform media are derived through the inverse scattering transform. The obtained solutions describe lump waves with time-dependent amplitudes and velocities. Dynamics of l-lump wave and interactions of two lump wave are illustrated. 展开更多
关键词 non-isospectral Kadomtsev-Petviashvili I equation inverse scattering transform lump solutions
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Performance of magnetorheological elastomer based torsional vibration isolation system for dynamic loading conditions
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作者 PRAVEEN Shenoy K KUCHIBHATLA Sai Aditya Raman +1 位作者 SINGH Abhishek Kumar GANGADHARAN K V 《Journal of Central South University》 SCIE EI CAS CSCD 2020年第1期144-154,共11页
Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attr... Vibration isolation is an effective method to mitigate unwanted disturbances arising from dynamic loading conditions. With smart materials as suitable substitutes, the conventional passive isolators have attained attributes of semi-active as well as the active control system. In the present study, the non-homogenous field-dependent isolation capabilities of the magnetorheological elastomer are explored under torsional vibrations. Torsional natural frequency was measured using the serial arrangement of accelerometers. Novel methods are introduced to evaluate the torsional stiffness variations of the isolator for a semi-definite and a motor-coupled rotor system. For the semi-definite system, the isolation effect was studied using the frequency response functions from the modal analysis. The speed-dependent variations for motor-coupled rotor system were assessed using the shift in frequency amplitudes from torque transducers. Finite element method magnetics was used to study the variations in the non-homogenous magnetic field across the elastomer. The response functions for the semi-definite rotor system reveal a shift in the frequency in the effect of the magnetic field. Speed-dependent variations in the frequency domain indicate an increment of 9% in the resonant frequency of the system. 展开更多
关键词 torsional vibration isolation semi-definite system magnetorheological elastomer speed-dependent isolation
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Precise Measurement of Subsurface Seismic Velocity Variation by Coda Wave Interferometry
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作者 Xia Yu Wang Baoshan +1 位作者 Ge Hongkui Chen Yong 《Earthquake Research in China》 2008年第4期366-373,共8页
A filed experiment was conducted continuously for three days,and the velocity variation was measured using coda wave interferometry.The measurement error is estimated to be around 10-4,which coincides well with the th... A filed experiment was conducted continuously for three days,and the velocity variation was measured using coda wave interferometry.The measurement error is estimated to be around 10-4,which coincides well with the theoretical error.The velocity variation during this period is up to 10-3.The relationship between velocity variation and changes in air temperature,barometric pressure and solid earth tide was analyzed with linear least square fitting.The velocity has no dependence on air temperature,but displayed change of the order of 10-6~10-7 when the barometer or earth tide changed one Pa. 展开更多
关键词 Coda wave interferometry Media property Correlation coefficient Velocity variation
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A Numerical Study of Tidal Asymmetry: Preferable Asymmetry of Nonlinear Mechanisms in Xiangshan Bay, East China Sea
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作者 XU Peng MAO Xinyan +1 位作者 JIANG Wensheng ZHOU Liangming 《Journal of Ocean University of China》 SCIE CAS 2014年第5期733-741,共9页
In-situ measurements in Xiangshan Bay, the East China Sea, show that the duration of the rising tide is shorter than that of the falling tide around the bay mouth, while it becomes much longer in the inner bay. A fini... In-situ measurements in Xiangshan Bay, the East China Sea, show that the duration of the rising tide is shorter than that of the falling tide around the bay mouth, while it becomes much longer in the inner bay. A finite volume coastal ocean model(FVCOM) with an unstructured mesh was applied to simulate the asymmetric tidal field of Xiangshan Bay. The model reproduced the observed tidal elevations and currents successfully. Several numerical experiments were conducted to clarify the roles of primary mechanisms underlying the asymmetric tidal field. According to the model results, the time-varying channel depth and nonlinear advection prefer shorter duration of the rising tide in Xiangshan Bay, while the time-varying bay width favors longer duration of the rising tide. The overtides generated by these two opposite types of nonlinear mechanisms are out of phase, resulting in smaller M4 amplitude than the sumfold of each individual contribution. Although the bottom friction as a nonlinear mechanism contributes little to the generation of overtide M4, it is regarded as a mechanism that could cause a shorter duration of the rising tide, for it can slow down the M2 phase speed much more than it slows down the M4 phase speed. The time-varying depth, nonlinear advection and bottom friction are dominating factors around the bay mouth, while the time-varying width dominates in the inner bay, causing the tidal elevation asymmetry to be inverted along the bay. 展开更多
关键词 FVCOM tidal asymmetry Xiangshan Bay nonlinear mechanisms
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Research on Wet Steam Spontaneous Condensing Flows Considering Phase Transition and Slip 被引量:1
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作者 Ke CUI Huan-long CHEN +1 位作者 Yan-ping SONG Hiroharu OYAMA 《Journal of Thermal Science》 SCIE EI CAS CSCD 2013年第4期320-326,共7页
A new dual-fluid model considering phase ansition and velocity slip was proposed in this paper and the Cunningham correction was used in the droplet resistance calculation. This dual-fluid model was applied to the num... A new dual-fluid model considering phase ansition and velocity slip was proposed in this paper and the Cunningham correction was used in the droplet resistance calculation. This dual-fluid model was applied to the numerical simulations of wet steam flow in a 2D LAVAL nozzle and in the White cascade respectively. The results of two simulations demonstrate that the model is reliable. Meanwhile, the spontaneous condensing flow in White cascade was analyzed and it infers that the irreversible loss caused by condensation accounts for the largest share (about 8.78% of inlet total pressure) in total pressure loss while the loss caused by velocity slip takes the smallest share (nearly 0.42%), and another part of total pressure loss caused by pneumatic factors contributes a less share than condensation, i.e. almost 3.95% of inlet total pressure. 展开更多
关键词 dual-fluid model wet steam spontaneous condensing flow LAVAL nozzle White cascade.
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Close-Contact Melting Around a Hot Sphere 被引量:1
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作者 YaojiangHu MinghengShi 《Journal of Thermal Science》 SCIE EI CAS CSCD 1997年第1期51-57,共7页
A more general model describing PCM close-contact melting outside a hot sphere is devel0ped withthe aid of introducing a parameter a and presenting a supplementary equation for the first time in thispaper. The governi... A more general model describing PCM close-contact melting outside a hot sphere is devel0ped withthe aid of introducing a parameter a and presenting a supplementary equation for the first time in thispaper. The governing integral-differential equations are solved by numerical method. The melt-filmthickness variation along the surface of sphere is obtained reasonably due to the consideration of theinterface shape more precisely. The calculation results of Peclet number, heat transferred and pressuredistribution are also compared with that in literature. The model presented in this paper can describethe whole close-contact region and the whole contact melting process. Closeeontact melting in spher-ical or cylindrical capsules to which the model can be extended is also discussed brielly. 展开更多
关键词 close-contact melting model melt-film thickness profile moving velocity of sphere
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Numerical Modeling of the Solidification Phase Change in a Pipe and Evaluation of the Effect of Boundary Conditions 被引量:1
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作者 A.Jalali A.F.Najafi 《Journal of Thermal Science》 SCIE EI CAS CSCD 2010年第5期419-424,共6页
A numerical solution to a two-dimensional model of flow and transient heat transfer involving solidification in a pipe has been established.Where the temperature of pipe wall is below the freezing point of fluid,phase... A numerical solution to a two-dimensional model of flow and transient heat transfer involving solidification in a pipe has been established.Where the temperature of pipe wall is below the freezing point of fluid,phase change of flowing fluid and the influence of different boundary condition,such as pipe wall temperature,initial temperature and inlet velocity has been taken into account.Also it has been investigated to elicit proper non-dimensional numbers to show the solidification proceeding results.Additionally comparing the two acceptable inlet conditions,show distinctions between velocity inlet and pressure inlet boundary condition in such problems,which affect the whole freezing process. 展开更多
关键词 Phase change SOLIDIFICATION Heat transfer
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