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1.
研究了稀土La对(Ag-Cu28)-25Sn-xLa合金微观结构的影响,并探讨了稀土La含量的变化在其凝固过程中的作用。采用高频感应加热熔炼,经水淬制得(Ag-Cu28)-25Sn-xLa合金。通过XRD,SEM,EDS等分析手段,研究了合金的物相组成、凝固组织及元素分布情况。研究结果表明:微量的稀土La足以改变(Ag-Cu28)-25Sn合金的凝固过程;La含量不大于0.5%时,合金的物相组成为Ag3Sn,Cu3Sn和Cu6Sn5相;当La含量不小于1.0%(质量分数)时,合金的物相组成为Ag3Sn和Cu3Sn;同时,随La含量的增加合金的凝固组织不断细化,且有利于Ag(Sn)固溶体初生相的析出。 相似文献
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采用喷雾干燥-热还原方法制备了纳米级93W-4.9Ni-2.1Fe复合粉末和添加了微量稀土La的复合粉末.研究了微量稀土La对合金性能和显微组织的影响.结果表明:微量稀土La的加入能够有效增加粉末的分散度;微量稀土La在合金中主要以中间相WxNixFexLax0x(摩尔比)的形式分布于粘结相中,该中间相在细化晶粒的同时对杂质元素Ca具有较好的亲和力,使合金性能得以提升.但随着过量La的增加,其生成的中间相容易在钨晶界和钨与粘结相的相界面上产生偏聚,降低了合金的界面结合强度,从而使合金性能降低. 相似文献
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通过真空感应炉和Gleeble—3800热模拟试验机研究了稀土对Fe-36Ni因瓦合金凝固组织和铸态热塑性的影响。结果表明:添加0.12%Ce+0.06%La混合稀土后,合金凝固组织显著细化,柱状晶变细变短,生长形态由直线状生长变为网篮状交错生长,等轴晶比例达40%。但添加0.12%Ce+0.06%La混合稀土后,合金在850~1 200℃温度区间的铸态热塑性严重恶化,这主要是由于在晶界上生成了大量Fe-Ni-Ce-La稀土晶间脆性相,削弱了晶界结合力,阻止了晶界移动,以致合金热塑性的恶化。 相似文献
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采用等温凝固实验、差示扫描量热仪(DSC)研究了K424合金的凝固行为以及冷却速度对其影响.利用光学显微镜、扫描电镜以及能谱分析仪分析了合金在不同温度等温凝固、不同冷却速度下的微观组织以及凝固后期的元素的偏析行为,确定K424合金的固相线、液相线和主要相的析出温度等凝固特性以及冷却速度对γ'相、MC碳化物以及共晶组织的影响规律.研究结果表明:K424合金的凝固顺序为:1345℃,γ相从液相析出,随后在1308℃析出MC型碳化物,在非平衡凝固条件下,共晶组织在1260℃析出,1237℃,凝固结束;共晶组织的形成与凝固末期Al、Ti元素的偏析行为以及冷却速度密切相关;随着冷却速度的增加,MC和共晶组织尺寸及数量均呈现先增大后减小的趋势;γ'相形貌从花瓣形状向规则立方及球形转变,尺寸也从2 μm减小至60 nm. 相似文献
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W. J. Boettinger D. Shechtman R. J. Schaefer F. S. Biancaniello 《Metallurgical and Materials Transactions A》1984,15(1):55-66
Electron beam solidification passes have been performed on a series of Ag-Cu alloys between 1 wt pct Cu and the eutectic composition
(28.1 wt pct Cu) at speeds between 1.5 and 400 cm per second. At low growth rates conventional dendritic or eutectic structures
are obtained. The maximum growth rate of eutectic structure is 2.5 cm per second. At high growth rates microsegregation-free
single phase structures are obtained for all compositions. The velocity required to produce this structure increases with
composition for dilute alloys and agrees with the theory of absolute stability of a planar liquid-solid interface with equilibrium
partitioning. For alloys between 15 and 28 wt pct Cu, the velocity required to produce the microsegregation-free extended
solid solution decreases with composition and is related to nonequilibrium trapping of solute at the liquid solid interface.
At intermediate growth rates for alloys with 9 wt pct Cu or greater, a structure consisting of alternating bands of cellular
and cell-free material is obtained. The bands form approximately parallel to the local interface.
On leave at the Center for Materials Research, The Johns Hopkins University, Baltimore, MD 21218. 相似文献
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利用机械合金化法制备(Ag-Cu28)-xSn系合金粉末,借助差示扫描量热仪、X-射线衍射仪、扫描电镜等,研究了Sn含量对合金熔化温度、球磨时间对合金粉末的物相组成及显微结构的影响。研究表明:Sn对合金的熔化温度有显著影响,随Sn含量增加合金熔化温度下降趋势减缓;当Sn含量为30%时,合金熔化温度最低为539.3℃。球磨40 h时,(Ag-Cu28)-30Sn粉料合金化完全,其物相组成为Ag4Sn、Cu3Sn和Cu6Sn5。球磨初始阶段(Ag-Cu28)-30Sn粉料颗粒异常长大,球磨至40 h时合金化完成,颗粒断裂和焊合达到平衡,合金粉末粒度均匀,平均粒径约为5~10μm。 相似文献
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Alan A. Luo Penghuai Fu Liming Peng Xiaoyu Kang Zhenzhen Li Tianyu Zhu 《Metallurgical and Materials Transactions A》2012,43(1):360-368
The solidification microstructure and mechanical properties of as-cast Mg-Al-Sn alloys have been investigated using computational
thermodynamics and experiments. The as-cast microstructure of Mg-Al-Sn alloys consists of α-Mg, Mg17Al12, and Mg2Sn phases. The amount of Mg17Al12 and Mg2Sn phases formed increases with increasing Al and Sn content and shows good agreement between the experimental results and
the Scheil solidification calculations. Generally, the yield strength of as-cast alloys increases with Al and Sn content,
whereas the ductility decreases. This study has confirmed an early development of Mg-7Al-2Sn alloy for structural applications
and has led to a promising new Mg-7Al-5Sn alloy with significantly improved strength and ductility comparable with commercial
AZ91 alloy. 相似文献
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运用电阻法和DSC热分析发现了CuSn30%合金熔体中存在不可逆的结构转变。在转变区间前后,通过熔体过热处理手段探索了这一结构变化对合金凝固过程及凝固组织的影响。结果表明,不可逆熔体结构的变化导致熔体凝固所需的过冷度增大,合金凝固组织变化明显,初生相和共析组织细化,分布弥散化。并从熔体结构转变角度对上述现象的作用机理进行了分析探讨。 相似文献
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Metallurgical and Materials Transactions A - Austenitic stainless steels such as 25Cr-35Ni-Nb, HP-Nb alloys are commonly used in high-temperature applications above 850 °C. The HP-Nb... 相似文献
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M. F. Zhu C. P. Hong D. M. Stefanescu Y. A. Chang 《Metallurgical and Materials Transactions B》2007,38(4):517-524
In this article, a front tracking (FT) model and a modified cellular automaton (MCA) model are presented and their capabilities
in modeling the microstructure evolution during solidification of aluminum alloys are demonstrated. The FT model is first
validated by comparison with the predictions of the Lipton–Glicksman–Kurz (LGK) model. Calculations of the steady-state dendritic
tip growth velocity and equilibrium liquid composition as a function of melt undercooling for an Al-4 wt pct Cu alloy exhibit
good agreement between the FT simulations and the LGK predictions. The FT model is also used to simulate the secondary dendrite
arm spacing as a function of local solidification time. The simulated results agree well with the experimental data. The MCA
model is applied to simulate dendritic and nondendritic microstructure evolution in semisolid processing of an Al-Si alloy.
The effect of fluid flow on dendritic growth is also examined. The solute profiles in equiaxed dendritic solidification of
a ternary aluminum alloy are simulated as a function of cooling rate and compared with the prediction of the Scheil model.
The MCA model is extended to the multiphase system for the simulation of eutectic solidification. A particular emphasis is
made on the quantitative aspects of simulations.
This article is based on a presentation made in the symposium ”Simulation of Aluminum Shape Casting Processing: From Design
to Mechanical Properties,” which occurred March 12–16, 2006, during the TMS Spring Meeting in San Antonio, Texas, under the
auspices of the Computational Materials Science and Engineering Committee, the Process Modeling, Analysis and Control Committee,
the Solidification Committee, the Mechanical Behavior of Materials Committee, and the Light Metal Division/Aluminum Committee. 相似文献
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Influence of Some Trace Elements on Solidification Path and Microstructure of Al-Si Foundry Alloys 总被引:1,自引:0,他引:1
Thomas Hartmut Ludwig Paul Louis Schaffer Lars Arnberg 《Metallurgical and Materials Transactions A》2013,44(8):3783-3796
In the present study, Ca, Ni, V, and Zn were added to a high purity binary Al-7wt pct Si and commercial purity A356 foundry alloy in the nominal range of 50 to 600 ppm in order to study their effect on the solidification path and the resultant microstructure. Thermal analysis was used to assess nucleation and growth of the various phases. It was found that Ca and Ni additions suppress characteristic temperatures associated with nucleation and growth of the eutectic by up to 4 and 1.5 K, respectively. Additionally, Ca was observed to modify the eutectic Si and a concentration as low as 39 ppm Ca was sufficient to precipitate the geometrically unfavored polyhedral Al2Si2Ca phase. Furthermore, Ni addition resulted in the formation of two intermetallic phases when the Ni concentration exceeded 300 ppm. These phases have been quantified as Al3Ni and Al9FeNi by SEM-EDS. V and Zn had no apparent effect on the cooling curve and the microstructure. Even though it could be shown that V accumulates preferably in β-Al5FeSi particles, V concentrations of 600 ppm were too low to have any influence on the phase’s morphology. 相似文献
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Liu N. Ding W. Wang X. J. Mu C. Du J. J. Liu L. X. 《Metallurgical and Materials Transactions A》2020,51(6):2990-2997
Metallurgical and Materials Transactions A - Fe25Ni25CoxMoy multi-principal-component alloys (MPCAs) are designed in this study; the ratio of Co and Mo is changed to study the effect on the... 相似文献
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(Ag—Cu28)80-Inx—Sn20-x合金焊粉的制备及熔化特性研究 总被引:1,自引:0,他引:1
用机械合金化法来制备(Ag-Cu28)80-Inx-Sn20-x合金焊粉。利用差示扫描量热仪(DSC)、X-射线衍射仪(XRD)及扫描电子显微镜(SEM)和Simple-PCI软件对制备合金粒子的熔化特性、物相、微观结构和粒度分布等进行表征分析。研究结果表明:机械合金化法可以有效的制备(Ag-Cu28)80-Inx-Sn20-x合金焊粉。组分为(Ag-Cu28)80-In10.5-Sn9.5合金焊粉的熔化温度最低为490.9℃,其物相组成主要为富Ag相和-βCu81Sn22相。球磨30 h,(Ag-Cu28)80-Inx-Sn20-x体系合金化完全。球磨至80 h,合金粉体的平均尺寸约为47.64μm,铺展率为110.76 cm2/g。 相似文献