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.

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.

Effect of Electromagnetic Stirring on the Reciprocating Wear Characteristics of A390 Alloy

2015 ◽  
Vol 830-831 ◽  
pp. 391-394
Author(s):  
G.L. Aswinikumar ◽  
V.R. Rajeev ◽  
K. Jayaraj ◽  
A. Ashok Kumar ◽  
Bibin Emmanuvel ◽  
...  
Keyword(s):  
Eutectic Silicon ◽  
Primary Silicon ◽  
Electromagnetic Stirring ◽  
Dry Sliding Wear ◽  
Wear Loss ◽  
Wear Characteristics ◽  
Contact Loads ◽  
Reciprocating Wear ◽  
A390 Alloy ◽  
Sliding Distance

Present study reports the effect of electromagnetic stirring (EMS) on reciprocating wear characteristics of A390 alloy. The microstructure features showed the refinement of eutectic silicon and reduction in size of primary silicon particles due to the effect of EMS. Hardness of the A390 alloy (100.28 BHN) prepared by EMS was higher than conventional A390 alloy (66.86 BHN). Reciprocating wear tests were carried out at different contact loads (15N to 90N) and speeds (0.2m/s to 1m/s) using pin-on-reciprocating plate tribometer for a constant sliding distance of 500m. As the reciprocating velocity increases from 0.2m/s to 1m/s, the wear loss of both EMS stirred and without stirred A390 alloys were found to decrease gradually up to the critical velocity 0.6m/s. It was noticed that above critical reciprocating velocity 0.6m/s, the wear loss was found to increase abruptly. Also, as the load increases from 15N to 90N, the wear loss of both the alloys were found to increase gradually up to 45N and thereafter abrupt increase in wear loss was noticed up to 90N. This clearly indicates a transition in the mode of wear from mild oxidative to severe metallic wear regime. Wear rate of without stirred A390 alloy in the region 45N to 90N showed predominant increase compared to EMS stirred A390 alloy. This trend suggests that EMS stirred A390 alloy is more coherent and stable under dry sliding wear conditions than without stirred A390 alloy.

Effect of Heat Treatment on Microstructure and Mechanical Properties of A390 Alloy

2013 ◽  
Vol 652-654 ◽  
pp. 1049-1053 ◽  
Author(s):  
Bao Li ◽  
Zhi Feng Zhang ◽  
Zhi Gang Wang ◽  
Jun Xu ◽  
Qiang Zhu
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Eutectic Silicon ◽  
Solution Treatment ◽  
Primary Silicon ◽  
Lamellar Morphology ◽  
Microstructure And Mechanical Properties ◽  
Heat Treated ◽  
Sharp Edges ◽  
A390 Alloy

In the present work, the effects of heat treatment on microstructure and mechanical properties of A390 alloy were investigated. The results show that the as-cast microstructure of A390 alloy mainly consists of primary silicon, α-Al, eutectic silicon and Al2Cu phase. The morphology of primary silicon is irregular polygonal block with sharp edges. Eutectic silicon exhibits a coarse plate-like and acicular morphology and the fishbone like Al2Cu phases are gathered at the grain boundary. During solution treatment, eutectic silicon undergoes fragmentation and spheroidization and T6 heat treatment has a profound effect on the dissolution of Cu and Mg. However, the morphology and size of primary silicon changes little. After the aging process, Al2Cu phases are precipited as lamellar morphology. As a result, the mechanical properties the heat treated A390 alloy increases significantly after T6 treatment.

Effect of Ca Level on the Formation of Silicon Phases during Solidification of Hypereutectic Al-Si Alloys

2013 ◽  
Vol 765 ◽  
pp. 117-122 ◽  
Author(s):  
Kawther Al-Helal ◽  
Yun Wang ◽  
Ian Stone ◽  
Zhong Yun Fan
Keyword(s):  
Nucleation And Growth ◽  
Impurity Level ◽  
Commercial Purity ◽  
Oxide Inclusions ◽  
Primary Si ◽  
Oxide Bifilms ◽  
Eutectic Si ◽  
High Level

In this paper the effect of Ca on the formation of Si phases during solidification of commercial purity Al-15Si alloy was studied. The Ca impurity level of the commercial purity alloy was 200 ppm which was sufficient to lead to a modified Al-Si eutectic. After the addition of K2SiF6 flux the Ca impurity level was 20 ppm which was insufficient to modify the eutectic Si, but primary Si was refined from 48 µm to 20 µm. The refinement of primary Si in Al-15Si alloy fluxed with K2SiF6, suggests that when Ca level is reduced to less than 20 ppm the impurity level of P (≈20 ppm) in commercial purity hypereutectic Al-Si alloys is sufficient to refine the primary Si without any deliberate addition of P. In the case of adding 0.5 wt.% Ca to the Al-15Si alloy, the eutectic Si was highly modified and the primary Si was coarse and irregular in morphology (unrefined). The addition of such a high level of Ca led to enhanced quantities of entrained oxide inclusions/bifilms. The first phase to solidify was Al2CaSi­2 which nucleated on the oxide bifilms. Primary Si then formed by nucleation and growth on the Al2­CaSi2 particles.

scholarly journals Refinement of Primary Silicon Crystals by Novel P-Doped γ-Al2O3 Particles in Solidification of Hypereutectic Al-Si Alloys

2016 ◽  
Vol 877 ◽  
pp. 550-557 ◽  
Author(s):  
Kawther Al-Helal ◽  
Ian Stone ◽  
Zhong Yun Fan
Keyword(s):  
Particle Size ◽  
Size Range ◽  
Average Particle Size ◽  
Primary Silicon ◽  
Average Particle ◽  
Commercial Purity ◽  
Particle Size Range ◽  
Silicon Crystals ◽  
Primary Si ◽  
Eutectic Si

P-doped γ-Al2O3 was found to be a potent substrate to nucleate primary silicon whilst good modification of the eutectic matrix is retained during solidification of hypereutectic Al-Si alloys. On using P-doped γ-Al2O3 could be a perfect and clean source of P without additional impurities. The optical micrographs show that the morphologies of primary silicon crystals in solidification of Al-18Si alloy are changed from irregular coarse morphologies to fine regular particles. The average particle size of primary Si decreased from 52 μm to 25 μm and 22 μm in adding P-doped α-Al2O3 and P-doped γ-Al2O3 respectively. It was clear that P-doped γ-Al2O3 led to good refinement of primary Si and the modification effect on eutectic Si was retained in solidification of commercial purity Al-18Si alloy. Adding P-doped γ-Al2O3 give a good primary Si refinement to Al-18Si alloy if compared with the addition of P and using finer P doped γ-Al2O3 powder give narrower particle size range similar to that of adding P.

scholarly journals INVESTIGATION OF THE INFLUENCE OF DIFFERENT MODIFIERS ON THE EUTECTIC SI IN THE COMPOSITION OF ALSI18 ALLOY

2021 ◽  
Vol 3 ◽  
pp. 261-265
Author(s):  
Ivan Panov ◽  
Boyan Dochev ◽  
Valentin Manolov ◽  
Angel Velikov ◽  
Vanya Dyakova
Keyword(s):  
Eutectic Silicon ◽  
Microstructural Analysis ◽  
Primary Silicon ◽  
Silicon Alloys ◽  
Aluminum Silicon Alloys ◽  
Size And Shape ◽  
Silicon Crystals ◽  
Different Types ◽  
Eutectic Si ◽  
Shape And Size

The structure of hypereutectic aluminum-silicon alloys consists of primary silicon crystals arranged in a eutectic matrix. In the present work the influence of different types of modifiers on the size and shape of the silicon crystals in the composition of the eutectic of the AlSi18 alloy has been studied. The classic for this type of alloys modifier (phosphorus), as well as the nanomodifiers SiC and nanodiamonds (ND) have been used. The results of the microstructural analysis show that the three modifiers used affect differently the shape and size of the eutectic silicon of the investigated alloy.

The Effect of Bubbling and AlCuP for Refining Primary Silicon at Al-18%Si Alloy

2007 ◽  
Vol 124-126 ◽  
pp. 1489-1492
Author(s):  
Jung Pyung Choi ◽  
Won Jung Kim ◽  
Tae Woon Nam ◽  
Eui Pak Yoon
Keyword(s):  
Primary Silicon ◽  
Nucleation Site ◽  
Optimum Treatment ◽  
Primary Si ◽  
Nucleation Sites ◽  
Stirring Time ◽  
Holding Temperature ◽  
Treatment Order

This paper investigates the effect of Bubbling and AlCuP on primary Si size in Al-18%Si alloy. Bubbling process and AlCuP treatment are effective for refining primary Si in hypereutectic Al-Si alloy. Both the bubble and AlCuP can be used as nucleation sites of primary Si. Many nucleation sites can make the size of primary Si decreased. So, this experiment suggests that the mix using of bubbling process and AlCuP treatment are more effective for nucleation site of primary Si. For deciding the optimum treatment order, the experiments are processed 3 kinds of order with varying stirring time and holding temperature; 1)AlCuP treatment and then bubbling process, 2)simultaneously using of bubbling process and AlCuP treatment, 3)bubbling process and then AlCuP treatment.

Monte Carlo Simulation of Precipitate Nucleation and Growth: Time Dependent Results

1988 ◽  
Vol 141 ◽  
Author(s):  
James P. Lavine ◽  
Gilbert A. Hawkins
Keyword(s):  
Monte Carlo ◽  
Crystalline Silicon ◽  
Three Dimensional ◽  
Nucleation Site ◽  
Nucleation And Growth ◽  
Lattice Points ◽  
Growth Time ◽  
Decay Kinetics ◽  
Time Step ◽  
Oxygen Atoms

AbstractA three-dimensional Monte Carlo computer program has been developed to study the heterogeneous nucleation and growth of oxide precipitates during the thermal treatment of crystalline silicon. In the simulations, oxygen atoms move on a lattice with randomly selected lattice points serving as nucleation sites. The change in free energy that the oxygen cluster would experience in gaining or losing one oxygen atom is used to govern growth or dissolution of the cluster. All the oxygen atoms undergo a jump or a growth decision during each time step of the anneal. The growth and decay kinetics of each nucleation site display interesting fluctuation phenomena. The time dependence of the cluster size generally differs from the expected 3/2 power law due to the fluctuations in oxygen arrival at and incorporation in a precipitate. Competition between growing sites and coarsening are observed.

scholarly journals Enhancement of the Mechanical Properties in Al–Si–Cu–Fe–Mg Alloys with Various Processing Parameters

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2150 ◽  
Author(s):  
Su-Seong Ahn ◽  
Sharief Pathan ◽  
Jar-Myung Koo ◽  
Chang-Hyun Baeg ◽  
Chan-Uk Jeong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Silicon Content ◽  
Compositional Analysis ◽  
Processing Parameters ◽  
Silicon Phase ◽  
X Ray ◽  
Primary Si ◽  
Transmission Electron ◽  
Eutectic Si

In this research, various processing conditions were implemented to enhance the mechanical properties of Al-Si alloys. The silicon content was varied from hypoeutectic (Si-10 wt.%) to eutectic (Si-12.6 wt.%) and hypereutectic (Si-14 wt.%) for the preparation of Al-XSi-3Cu-0.5Fe-0.6 Mg (X = 10–14%) alloys using die casting. Subsequently, these alloys were hot-extruded with an optimum extrusion ratio (17:1) at 400 °C to match the output extruded bar to the compressor size. An analysis of the microstructural features along with a chemical compositional analysis were carried out using scanning electron microscope along with energy dispersive X-ray spectroscopy and transmission electron microscope. The SEM micrographs of the extruded samples displayed cracks in primary Si, and the intermetallic (β-Al5FeSi) phase was fragmented accordingly. In addition, the silicon phase was homogenously distributed, and the size remained constant. The mechanical properties of the extruded samples were enhanced by the increase of silicon content, and consequently the ductility decreased. By implementing proper T6 heat treatment parameters, coherent Al2Cu phases were formed in the Al matrix, and the Si phase was gradually increased along with the silicon content. Therefore, high tensile strength was achieved, reaching values for the Al-XSi-3Cu-0.5Fe-0.6Mg (X = 10–14%) alloys of 366 MPa, 388 MPa, and 420 MPa, respectively.

scholarly journals Investigation on Microstructures and Mechanical Properties of the Hypoeutectic Al-10Si-0.8Fe-XEr Alloy

Scanning ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Peng Tang ◽  
Yiyuan Liu ◽  
Yanjun Zhao ◽  
Zhiliu Hu ◽  
Huachun Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Secondary Phase ◽  
Metallographic Analysis ◽  
Analysis Techniques ◽  
Microstructure Modification ◽  
Primary Si ◽  
Eutectic Si ◽  
Second Phases ◽  
The Mean

In this paper, the effect of Er addition (0.2, 0.5, 0.65, 0.8, 1.0, and 1.5 wt. %) on the microstructure evolution and tensile properties of as-cast hypereutectic Al-10Si-0.8Fe alloy was investigated. The phases and their morphologies in these alloys were identified by XRD and SEM equipped with EDX with the help of metallographic analysis techniques; the length of the secondary phase (LSP) and secondary dendrite arm spacing (SDAS) of α-Al grain were quantified. The results indicated that the second phases (primary Si, eutectic Si, and iron-rich phases) and α-Al grain were significantly refined when the addition of Er increased from 0 to 0.8 wt. %. The mean LSP and SADS values were decreased to a minimum value when the Er addition reached 0.8 wt. %. However, the second phases and α-Al grain became coarser when the level of Er increased more than 0.8 wt. %. The analysis of XRD shows that Er mainly exists in the form of Er2Si compound. The microstructure modification also has a significant effect on the mechanical properties of the alloy. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) increase from 52.86 MPa, 163.84 MPa, and 3.45% to 71.01 MPa, 163.84 MPa, and 5.65%, respectively. From the fracture surface, the promotions of mechanical properties are due to the dispersion and pinning reinforcement caused by the Er2Si phase.

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