scholarly journals Effect of cooling rate on microstructure of B2-NiSc intermetallics

2019 ◽  
Vol 39 (3) ◽  
pp. 236-242
Author(s):  
Zhipeng Yuan ◽  
Hao Chen ◽  
Hongbao Cui ◽  
Yatao Chang ◽  
Xuefeng Guo
Keyword(s):  
Thin Plate ◽  
Volume Fraction ◽  
Solidification Rate ◽  
Centrifugal Casting ◽  
Critical Dimension ◽  
Eutectic Structure ◽  
Primary Phase ◽  
Solidification Structure ◽  
Second Phase ◽  
Lamellar Eutectic Structure

Ni-50at%Sc alloy was prepared by centrifugal casting method. Volume fraction, the actual content of B2-NiSc and second phase Ni2Sc in alloy were analyzed with an Image-Pro Plus software. The cooling rates for the solidified thin plate with thickness of 2.65mm, 1.2mm, 0.75mm and 0.35 mm are 1164, 2570, 4112 and 8811 K·s1, respectively. It is found that d=0.5 mm was an critical dimension which corresponds to an abrupt change in the solidification rate. It is also found that (Ni2Sc+NiSc)eutectic was dispersed at grain boundary or between dendritic arms due to the loss of Sc element during melting. While d＞0.5mm (corresponding to the thin plate with thickness of 0.75mm, 1.20mm and 2.65 mm), the solidification structure consists of primary phase B2-NiSc and (Ni2Sc+NiSc)eutectic. While d ＜ 0.5mm (corresponding to the thin plate with thickness of 0.35 mm), the solidification structure is composed of fine globular B2-NiSc and relatively small amounts of (Ni2Sc+NiSc)eutectic. Based on the phase volumetric analyzing of the microstructure with an Image-Pro Plus software, the loss of Sc element during melting was about 3.01~3.10 at%. The eutectic NiSc in the lamellar eutectic structure together with the primary phase B2-NiSc form a larger single phase NiSc, while Ni2Sc with the form of particles is distributed on the grain boundaries after (970 ℃, 72 h) homogenization heat treatment.

Variation of Microstructure and Properties of Re-7075 Al Alloy after Homogenizing Annealing

2012 ◽  
Vol 463-464 ◽  
pp. 198-202
Author(s):  
Ju Guo Zhang ◽  
Hong Bin Zhu
Keyword(s):  
Volume Fraction ◽  
Optical Microscope ◽  
Primary Phase ◽  
Dendritic Segregation ◽  
Al Alloy ◽  
Second Phase ◽  
Microstructure And Properties ◽  
Analytical Instruments ◽  
Homogenizing Annealing ◽  
7075 Al Alloy

The variation of microstructure and properties of RE-7075 Al alloy after homogenizing annealing were studied by some modern analytical instruments which including OM(optical microscope),SEM(scanning electron microscopy),EDS(energy dispersive spectroscopy ), Brinell hardness and conductivity meter of SIGMASCOPE SMP10 type in this experiment. The results shows that the alloy′s microstructure was uniform ,reduced the volume fraction of second phase,increased supersaturation of matrix and eliminated gradually dendritic segregation in homogenizing annealing state. The primary phase of matrix microstructure contain α(Al),T(Al2Mg3Zn3) and grain boundary microstructure include α(Al),Al2Cu,AlCuMg4La4 after homogenizing annealing.Compared with as cast condition,the conductivity and the hardness reduced after homogenizing annealing.

Numerical Study on the Impact of Second Phase Content on the Solidification of Al-Pb Hypermonotectic Alloys

2017 ◽  
Vol 896 ◽  
pp. 209-215 ◽  
Author(s):  
Zhi Qiang Kang ◽  
Yu Bo Zhang ◽  
Xue Yang ◽  
Guo Hui Feng ◽  
Lin Zhang
Keyword(s):  
Temperature Field ◽  
Volume Fraction ◽  
Numerical Study ◽  
Immiscible Liquid ◽  
Conservation Equation ◽  
Solidification Microstructure ◽  
Solidification Structure ◽  
Second Phase ◽  
Phase Content ◽  
The Impact

Based on the Euler-Euler method and the conservation equation, a mathematical model for describing the non-steady processes of mass transfer, transmission, heat transfer, solute transport and nonstationary process of nucleation in liquid-liquid separation of Al-Pb monotectic alloys was established. The influence of the second phase content on the solidification microstructure of Al-Pb alloy was analyzed by numerical simulation by combining the calculated temperature field and velocity field with the kinetic equation of controlling solidification microstructure evolution. The results show that the lower the second phase content is, the more uniform the temperature field distribution is, and the lower the velocity of the second phase droplets is. The average diameter and volume fraction of the second phase droplets in the Al-5wt%Pb alloy samples were lower than that in the Al-10wt%Pb alloy samples under the same conditions. It is concluded that the lower the content of the second phase, the liquid - liquid phase separation and decomposition behavior of liquid immiscible liquid in the immiscible zone are relatively slow, and the more easily the droplets of the second phase are distributed uniformly in alloy solidification structure of the matrix.

Characterization of a Functionally Graded Hypereutectic Al-Si Alloy Produced by Centrifugal Method

2008 ◽  
Vol 47-50 ◽  
pp. 865-868 ◽  
Author(s):  
Emad Oveisi ◽  
Farshad Akhlaghi
Keyword(s):  
Volume Fraction ◽  
Rotation Axis ◽  
Eutectic Silicon ◽  
Centrifugal Casting ◽  
Eutectic Structure ◽  
Functionally Graded ◽  
The Other ◽  
Al Alloy ◽  
Sample Length

In the present study, Al-Si samples with a graded structure were produced via horizontal centrifugal casting. The distribution of primary and eutectic silicon particles within the produced specimens was investigated by optical microscopy. The microstructure of one end of the sample (closed to rotating axis) consisted of primary Si particles distributed within a eutectic matrix. The volume fraction of these particles decreased towards the other end of the sample and exhibited mostly primary Al-α and eutectic structure. Microhardness and macrohardness measurements conducted along the sample length showed a gradual decreasing value from one end (near the rotation axis) towards the other end of sample demonstrating functionally graded properties. These results were rationalized in terms of the lower density of Si compared to Al alloy which provided the movement of Si particles under the action of centrifugal forces during rotation.

Numerical Study on the Impact of Cooling Rate on the Solidification of Al-Bi Hypermonotectic Alloys

2017 ◽  
Vol 727 ◽  
pp. 111-116
Author(s):  
Zhi Qiang Kang ◽  
Xue Yang ◽  
Guo Hui Feng ◽  
Lin Zhang
Keyword(s):  
Cooling Rate ◽  
Volume Fraction ◽  
Numerical Study ◽  
Solidification Rate ◽  
Average Diameter ◽  
Euler Method ◽  
Solidification Structure ◽  
Diffusional Growth ◽  
Gravity Settling ◽  
The Impact

A numerical model describing the liquid-liquid phase transformation of the nucleation, the diffusional growth, Ostwald coarsening and macro-transport phenomena was established based on Euler-Euler method. The microstructure development of Al-Bi alloys in different solidification rate has been simulated by coupling the calculated temperature and velocity fields with the kinetic equation which controls the microstructure evolution. The results showed that average diameter difference of L2 phase droplets between top and bottom of samples in low cooling rate increased by 151 % than in high cooling speed and the maximum volume fraction of the droplets at the bottom of the sample in low cooling rate much higher than in high cooling rate. Analysis that the bigger cooling rate can shorten the action time which caused by gravity settling and collisions coagulation of the droplets, and then improves the macrosegregation of solidification structure in favor of uniform distribution of the solidification structure.

Hot Compression Deformation Behaviors and Microstructure Evolution for Brittle Au-20Sn Eutectic Alloy

2014 ◽  
Vol 789 ◽  
pp. 409-414 ◽  
Author(s):  
Wei Zhang ◽  
Yong Mao ◽  
Jia Jia Song ◽  
Jin Xin Guo ◽  
Si Yong Xu
Keyword(s):  
Eutectic Alloy ◽  
Eutectic Structure ◽  
Primary Phase ◽  
Hot Compression ◽  
Lamellar Eutectic ◽  
Hot Compression Test ◽  
Deformation Behaviors ◽  
Fully Lamellar ◽  
Lamellar Eutectic Structure ◽  
Large Primary

The hot compression test of Au-20Sn alloys with different solidification structures was carried out. The deformation behaviors and microstructure evolutions during hot compression were investigated. The results indicate that the fine fully lamellar eutectic structure without primary phase exhibited a very low yielding stress and a low stress platform, while the coarse lamellar with large primary Au5Sn phase showed rather high in that value. After compression, the lamellar eutectic tended to be equiaxed due to dynamic recrystallization, the large primary phase became separate dendrites or split into small dendrites, and the small roselike primary phase partly dissolved in the eutectic matrix. The rate of recrystallization also increased as the primary phase eliminated and lamellae was refined. It is suggested that refining eutectic lamellae and eliminating the primary Au5Sn phase in the as-cast microstructure by solidification optimization are an effective way to improve the workability greatly for brittle Au-20Sn eutectic alloy.

Grain Refinement in Titanium-Erbium Alloys

1974 ◽  
Vol 32 ◽  
pp. 522-523
Author(s):  
B. B. Rath ◽  
J. E. O'Neal ◽  
R. J. Lederich
Keyword(s):  
Electron Microscopy ◽  
Size Distribution ◽  
Grain Refinement ◽  
Grain Growth ◽  
Volume Fraction ◽  
Pure Titanium ◽  
Systematic Investigation ◽  
Second Phase ◽  
Titanium Matrix ◽  
Average Size

Addition of small amounts of erbium has a profound effect on recrystallization and grain growth in titanium. Erbium, because of its negligible solubility in titanium, precipitates in the titanium matrix as a finely dispersed second phase. The presence of this phase, depending on its average size, distribution, and volume fraction in titanium, strongly inhibits the migration of grain boundaries during recrystallization and grain growth, and thus produces ultimate grains of sub-micrometer dimensions. A systematic investigation has been conducted to study the isothermal grain growth in electrolytically pure titanium and titanium-erbium alloys (Er concentration ranging from 0-0.3 at.%) over the temperature range of 450 to 850°C by electron microscopy.

Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

1988 ◽  
Vol 46 ◽  
pp. 550-551
Author(s):  
R. E. Franck ◽  
J. A. Hawk ◽  
G. J. Shiflet
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Grain Growth ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

Effects on the microstructure and mechanical properties of Sn-0.7Cu lead-free solder with the addition of a small amount of magnesium

2016 ◽  
Vol 23 (6) ◽  
pp. 641-647
Author(s):  
Her-Yueh Huang ◽  
Chung-Wei Yang ◽  
Yu-Chang Peng
Keyword(s):  
Mechanical Properties ◽  
Aging Process ◽  
Intermetallic Layer ◽  
Eutectic Structure ◽  
Contact Angles ◽  
Solidification Structure ◽  
Lead Free Solder ◽  
Bulk Alloy ◽  
Scanning Calorimetry ◽  
Free Solder

AbstractThe influence of a small amount of magnesium (only 0.01 wt.%) added to the Sn-0.7Cu solder alloy during the aging process of microstructural evolution is studied along with the mechanical properties of the alloy. The experimental results indicate that the addition of magnesium decreases the tensile strength of the solders but improves their elongation. The solidification structure of eutectic Sn-0.7Cu consists of β-Sn, and the eutectic structure, which has extremely fine intermetallic nodules, Cu6Sn5, is located in the interdendritic region. When the magnesium is added to the Sn-0.7Cu alloy, the Sn dendrites become slightly coarser; in comparison, the melting point of the Sn-0.7Cu-0.01Mg alloy decreased by 2°C for the differential scanning calorimetry results of bulk alloy samples. Sn-0.7Cu-0.01Mg exhibits the lowest contact angles and the widest spreading areas. After aging, the Sn-0.7Cu and Sn-0.7Cu-0.01Mg solders show significant changes in strength, mainly because of the obvious increase in the thickness of the Cu6Sn5 intermetallic layer.

Effects of Electric Pulse Modification on As-Cast Texture of Pure Copper

2010 ◽  
Vol 29-32 ◽  
pp. 1894-1897
Author(s):  
Jin Gang Qi ◽  
Jian Zhong Wang ◽  
Xing Jiang Liu ◽  
Shan Dai
Keyword(s):  
Volume Fraction ◽  
Vertical Section ◽  
Electric Pulse ◽  
Pure Copper ◽  
Solidification Structure ◽  
Crystal Direction ◽  
Ingot Axis ◽  
Maximum Value ◽  
Typical Type ◽  
Orientation Density

The modification of liquid metal by electric pulse (EP or EPM) is a novel method for improvement of solidification structure. In this study, the as-cast texture of EP-modified pure copper was investigated by using X-ray Schulz backscattered method. The experimental results show that the as-cast texture of EP-modified pure copper is dissimilar with that of the unmodified. The unmodified mainly exhibits a type of {110}<001> texture, and the maximum value of orientation density is 10.07, in the plane that parallel to the vertical section along the ingot axis, the <110> crystal direction has the most volume fraction of 27.18%; By contrast, the as-cast texture of EP-modified pure copper shows a typical type of {102}<001>, and the maximum value of orientation density is 12.88, at the same time, the corresponding <102> crystal direction changes to be the most volume fraction and its value is 22.82%. These facts indicate that the crystal orientation (texture) of solidification structure could be altered by EPM, and EPM technology would thus influence the following metal formability.

Study on the Influence of Different Pulse Temperatures on Al-22%Si Alloy Solidification Structure

2011 ◽  
Vol 299-300 ◽  
pp. 566-571
Author(s):  
Zuo Fu Zhao ◽  
Jian Zhong Wang ◽  
Jin Gang Qi ◽  
Shan Dai ◽  
Dong Jun Zhang
Keyword(s):  
Volume Fraction ◽  
Electric Pulse ◽  
Primary Silicon ◽  
Electrical Pulse ◽  
Solidification Structure ◽  
Alloy Solidification ◽  
Modification Effect ◽  
Electric Pulse Modification ◽  
Average Size

Taking the hypereutectic Al-Si alloy as the research object, the fading characteristics of Al-22% Si alloy at different pulse temperatures are investigated in this paper in order to analyze the mechanism of electrical pulse modification to the alloy. We can get the conclusion by observing the microstructure of the sample, measuring the microhardness and calculating the volume fraction and the average size of primary silicon: at different pulse temperatures, the effect of electric pulse modification is fading with static duration prolonging; meanwhile, with the temperature upward, the modification effect and fading trends to be weak, which indicates the best pulse temperature is one of the important factors to influence the modification effect.

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