Modification of Eutectic Si in Hypoeutectic Al-Si Alloys with Erbium Addition

2016 ◽  
Vol 718 ◽  
pp. 139-142 ◽  
Author(s):  
Tanawat Tantiwaitayaphan ◽  
Phromphong Pandee ◽  
Chaowalit Limmaneevichitr
Keyword(s):  
Thermal Analysis ◽  
Eutectic Silicon ◽  
Nucleation And Growth ◽  
Significant Modification ◽  
Eutectic Si ◽  
Microstructure Examination ◽  
Eutectic Nucleation ◽  
Eutectic Undercooling

Effect of erbium (Er) on the eutectic Si morphologies in hypoeutectic Al-Si based alloys was investigated using thermal analysis and microstructure examination. The microstructural observations show that the addition of Er causes significant modification of the eutectic silicon morphology from a coarse plate-like to a fine fibrous one. Furthermore, the results of thermal analysis reveal that the addition of Er decreased the temperatures of eutectic nucleation and growth, and increased the eutectic undercooling. The eutectic undercooling caused by the presence of Er plays an important role in the modification of eutectic silicon.

scholarly journals Simultaneous Refinement of Primary Si and Modification of Eutectic Si in A390 Alloy Assisting by Sr-Modifier and Serpentine Pouring Channel Process

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3109 ◽  
Author(s):  
Pengyu Yan ◽  
Weimin Mao ◽  
Jing Fan ◽  
Bingkun Wang
Keyword(s):  
Eutectic Silicon ◽  
Primary Silicon ◽  
Interface Energy ◽  
Nucleation Site ◽  
Nucleation And Growth ◽  
Dominant Factor ◽  
Channel Process ◽  
Primary Si ◽  
Eutectic Si ◽  
A390 Alloy

In this study, A390 alloy was prepared using the combined process of a water-cooled copper serpentine pouring channel (SPC) and strontium (Sr) modifier, in order to simultaneously refine primary silicon (Si) and modify eutectic silicon (Si). The nucleation and growth mechanisms of the Si phase were discussed by morphology analysis and non-isothermal analytical kinetics. The results indicate that the size of primary Si is refined to 25.2–28.5 µm and the morphology of eutectic Si is modified from acicular into fibrous. The serpentine pouring channel process stimulates primary Si nucleation due to chilling effect and has no influence on eutectic Si nucleation. Impacts of Sr-modifier on primary and eutectic Si are similar, including three aspects: (1) poisoning of the nucleation site; (2) decreasing the interface energy between Si phase and liquid; (3) raising the activation energy for diffusion across solid-liquid interface. The content of Sr determines which one of the three aspects mentioned above is the dominant factor to promote or restrain the nucleation and growth of the primary and eutectic Si in hypereutectic Al-Si alloy.

Study on Eutectic Microstructure and Modification Mechanism of Al-Si Alloys

2016 ◽  
Vol 877 ◽  
pp. 97-103
Author(s):  
Jian Xun Chen ◽  
Meng Jie Lu ◽  
Shu Sen Wu ◽  
Shu Lin Lü
Keyword(s):  
Thermal Analysis ◽  
Eutectic Silicon ◽  
Eutectic Growth ◽  
Cooling Curve ◽  
Long Period ◽  
Computer Aided ◽  
Eutectic Si ◽  
Improvement Effect ◽  
Effective Additive ◽  
Addition Amount

Sb is an effective additive to modify eutectic Si of Al-Si alloys and the modification mechanism has not yet been studied very clearly. In this paper, computer aided cooling curve thermal analysis and microstructure assessment were carried out to investigate the modification effects of Sb on Al7SiMg alloy. The results show that the Sb addition amount of 0.1~0.25% has improvement effect on eutectic Si morphology, which can be further confirmed from the thermal analysis results. The addition of Sb decreases the eutectic growth temperature by 5 °C to 7.8 °C, indicating an undercooling effect resulted from Sb modification. Compared to that of short rods, a better eutectic Si morphology of nearly granular particles can be obtained in a faster cooling rate. The length of silicon has been gradually shortened as holding time increased to 2.5 h from 0.5 h, which means a long period modification effect of Sb in Al-Si alloys. Owing to undercooling resulted from Sb addition in Al-Si alloys, the refinement structure of eutectic silicon can be achieved.

Thermal Analysis and Microstructure Comparison Between A356 Aluminum Alloy and A356/15%vol. SiCP Cast Composite Modified with Strontium

2007 ◽  
Vol 560 ◽  
pp. 47-52 ◽  
Author(s):  
E. Trejo E. ◽  
J.A. García-Hinojosa ◽  
M.K. Surappa ◽  
E. Rodríguez
Keyword(s):  
Thermal Analysis ◽  
Aluminum Alloy ◽  
Eutectic Growth ◽  
Matrix Alloy ◽  
Eutectic Structure ◽  
A356 Aluminum Alloy ◽  
The Matrix ◽  
Eutectic Nucleation ◽  
A356 Aluminum ◽  
Eutectic Undercooling

A study of the effect of strontium on some solidification parameters, such as eutectic nucleation temperature, eutectic growth temperature, eutectic undercooling temperature and eutectic undercooling time, has been carried out using thermal analysis for a composite reinforced with 15 vol. % SiCP and, for comparison, for an A356 aluminum alloy. The composite is prepared by the melt stirring technique with a SiC particle size of 38 μm. Thermal analysis results show that the presence of SiCP in the unmodified A356 aluminum alloy increases the eutectic growth temperature (TE) and the eutectic nucleation temperature (TNucl); on the contrary, SiCP decreases the eutectic undercooling temperature (θ) and the eutectic undercooling time (tE). These phenomena suggest that SiC particles give favorable conditions for the growth of eutectic silicon. On the other hand, the modification with strontium of the composite material, although showing basically the same effect on the eutectic parameters as the one described for the A356 aluminum alloy, brings about certain differences due to the presence of the SiC particles. Microstructural analysis shows that the eutectic structures in the composite are coarser than those of the matrix alloy and they do not have the classic fibrous eutectic shape obtained in the matrix alloy. For the matrix alloy, when the Sr concentration increases beyond the quantity required to obtain a well-modified structure, the eutectic structure suffers a gradual coarsening or a reversion from fine fibrous silicon to coarser silicon; subsequently, when the Sr concentration is higher than 0.068%, Al2Si2Sr particles are produced. In the composite material there is also a gradual coarsening of the eutectic structure, although the appearance of Al2Si2Sr particles is just seen when the Sr concentration reaches 0.106%.

Modification of Al-Si Microstructure - The Al-Si-Sr Phase Diagram from 0–20 WT. % Si and 0–5.0 WT. % Sr

1982 ◽  
Vol 19 ◽  
Author(s):  
M. D. Hanna ◽  
A. Hellawell
Keyword(s):  
Thermal Analysis ◽  
Phase Diagram ◽  
Liquid Metal ◽  
Alkali Metal ◽  
Alkaline Earth ◽  
Liquidus Surface ◽  
Eutectic Silicon ◽  
Alkaline Earth Metals ◽  
Current Interest

ABSTRACTIt is well known that the morphology of primary and eutectic silicon resulting from solidification is sensitive to minor impurity additions: “modification” by alkali and alkaline earth metals is common foundry practice and the use of strontium is of recent and current interest because its effect is retained in liquid metal for relatively long times. The mechanism for modification remains obscure and is not necessarily the same from one elemental addition to the next, but it is essential to separate the equilibrium and kinetic influences if the phenomenon is to be better understood. Accordingly, the liquidus surface and eutectic reactions have been located in the relevant part of the Al-Si-Sr system by careful thermal analysis and the results correlated with the microstructure. Comparison is made with the parallel behavior of alkali metal additions.

Effect of Titanium on Microstructure and Solidification Behavior of Gray Irons

2020 ◽  
Vol 987 ◽  
pp. 177-181
Author(s):  
Sarum Boonmee ◽  
Kittirat Worakhut ◽  
Preecha Maneelum
Keyword(s):  
Thermal Analysis ◽  
Fine Particles ◽  
Eutectic Mixture ◽  
Solidification Behavior ◽  
Titanium Addition ◽  
Thermal Analysis Technique ◽  
Graphite Particles ◽  
Analysis Technique ◽  
Eutectic Undercooling ◽  
Ti Addition

This study investigates the microstructure and the solidification behavior of titanium-alloyed gray irons. Thermal analysis technique was used to identify the Temperature of Liquidus Arrest (TLA), the Temperature of Eutectic Undercooling (TEU) and the Temperature of the Eutectic Recalescence (TER). It was found that the titanium addition promoted the formation of the primary austenite causing the larger difference in TLA and TEU. In addition, titanium encouraged the refining of eutectic mixture. The SEM showed the graphite particles were refined with increasing titanium. Fine particles of titanium-containing compound were readily observed throughout the microstructure. The hardness as high as 176 HB was achieved at 0.495%Ti addition.

Mechanical Properties and Fracture Behavior of Indirect Squeeze-Cast A354 Alloy Using Local Pressurization

2016 ◽  
Vol 850 ◽  
pp. 502-510
Author(s):  
Hai Jun Liu ◽  
Lie Jun Li ◽  
Jian Wei Niu ◽  
Ji Xiang Gao ◽  
Xue Wen Chen
Keyword(s):  
Mechanical Properties ◽  
Tensile Properties ◽  
Fracture Behavior ◽  
Eutectic Silicon ◽  
Solidification Rate ◽  
Fracture Morphology ◽  
Shrinkage Cavity ◽  
Squeeze Cast ◽  
Ductile Mode ◽  
Eutectic Si

The effect of local pressurization on mechanical properties and fracture behavior of indirect squeeze-cast A354 alloy has been investigated. As compared to conventional process, the porosity and shrinkage cavity for heavy sectioned squeeze castings were improved by the indirect squeeze casting, while its tensile properties were inferior to other parts of the casting. That is mainly due to that inhomogeneous eutectic Si particles within strip, angular and fragment shapes distribute in bulky α-Al cells, which is caused by slower solidification rate. After T6 treatment, the fragmentation and spheroidization of the eutectic silicon happened. Under this situation, the effect of fragmentation on α-Al matrix reduced. Tensile properties of the casting (both local pressurization part and non-local pressurization part) were enhanced greatly, by 36.8% and 25.4%, respectively. Fracture analysis results show that the type of fracture morphology is changed from mixed mode of brittle cleavage and ductile to ductile mode after T6-treatment.

scholarly journals Effect of Sr-P Interaction on the Microstructure and Tensile Properties of A413.0 Type Alloys

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
A. M. Samuel ◽  
H. W. Doty ◽  
S. Valtierra ◽  
F. H. Samuel
Keyword(s):  
Heat Treatment ◽  
Tensile Properties ◽  
Solution Heat Treatment ◽  
Eutectic Silicon ◽  
Low Magnesium ◽  
The Third ◽  
Wide Range ◽  
Eutectic Si ◽  
Second Peak ◽  
Silicon Particles

The present study was performed on low magnesium A413.0 type alloys. The results show that strontium (Sr) is mainly concentrated in the silicon particles. Overmodification occurs when Sr precipitates in the form of Al2SrSi2, which takes place over a wide range of temperatures. The first peak occurs following the precipitation ofα-Al, the second peak is merged with the precipitation of eutectic silicon (Si), and the third peak is a posteutectic reaction. Introduction of phosphorus (P) to Sr-modified alloys leads to the formation of (Al,P,Sr)2O5compound, which reduces the modification effectiveness of Sr. Therefore, in the presence of P, the amount of added Sr should exceed 200 ppm. For the same levels of P, the tensile parameters of well modified alloys (233 ppm Sr) are relatively higher than those partially modified with Sr (about 60 ppm Sr) containing the same amount of P. During solution heat treatment, coarsening of the eutectic Si particles occurs by the growth of some particles at the expense of the dissolution of the smaller ones, as well as by the collision of nearby particles.

Modification Effects of Sb on Al7SiMg Alloy Measured with Cooling Curve Analysis

2016 ◽  
Vol 879 ◽  
pp. 2113-2118 ◽  
Author(s):  
Shu Sen Wu ◽  
Meng Jie Lü ◽  
Jian Xun Chen ◽  
You Wu Mao ◽  
Shu Lin Lü
Keyword(s):  
Thermal Analysis ◽  
Growth Temperature ◽  
Curve Analysis ◽  
Cooling Curve ◽  
Eutectic Solidification ◽  
Microstructure Observation ◽  
Modification Effect ◽  
Cooling Curve Analysis ◽  
Computer Aided ◽  
Eutectic Si

The modification mechanism of Sb on eutectic Si phase of Al-Si alloys was not understood very well. In this paper the modification effects of Sb on Al7SiMg alloy were investigated by computer aided cooling curve thermal analysis coupled with microstructure observation. The results show that the addition of Sb with 0.1%~0.25% amount has refining effect on eutectic Si phase, and this modification effect can be recorded by the cooling curve. The addition of Sb decreases the growth temperature of the eutectic solidification (TEG) by 5.0 °C to 7.8 °C, and this indicates that there is an undercooling effect with Sb modification. Moreover, faster cooling rate can obtain more superior morphology of eutectic Si, which can be changed from short rod to nearly granular particles. The morphology of eutectic Si is nearly unchanged with holding time extending from 0.5h to 2.5h, which means Sb has long modification effect for Al-Si alloys.

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