scholarly journals Research on Microstructure and Growth Mechanism of Different Primary Silicon in Hypereutectic Aluminum Alloy

2022 ◽  
Vol 2152 (1) ◽  
pp. 012022
Author(s):  
Gaozhan Zhao ◽  
Zhihui Xing ◽  
Ming Li ◽  
Shiqing Gao ◽  
Jianquan Tao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Growth Mechanism ◽  
Eutectic Silicon ◽  
Primary Silicon ◽  
Phase Growth ◽  
Silicon Phase ◽  
Tetrahedral Crystal ◽  
Impurity Elements ◽  
Growth Methods ◽  
Cast Microstructure

Abstract The as-cast microstructure of a typical hypereutectic Al-25Si alloy was studied, and the growth mechanism of different primary silicon phases was analyzed. The results show that the as-cast microstructure phase composition of the alloy is mainly primary silicon and eutectic silicon. Primary silicon is mainly petal-like, massive and other complex polyhedrons, and there are a lot of cavities, cracks and other defects in the interior and boundary; Eutectic silicon is coarse and long needle-like, and the distribution is relatively messy, which seriously deteriorates the mechanical properties and cutting performance, and hinders the further application of the alloy in the field of lightweight pistons. Petal-shaped primary silicon is grown by combining five tetrahedral crystal nuclei in the melt into a decahedron, while bulk primary silicon is mainly caused by the unbalanced aggregation of impurity elements. And these two types of silicon phase growth methods are related to the twin groove growth mechanism, which is the result of a combination of multiple mechanisms.

scholarly journals Effect of Rare Earth Upon As-Cast Microstructure and High Temperature Performance of ZA40 Alloy

2014 ◽  
Vol 8 (1) ◽  
pp. 251-256
Author(s):  
Jiaming Ji ◽  
Guocui Meng ◽  
Yuanyong Lu ◽  
Honghong Shao ◽  
Dongqing Gu
Keyword(s):  
Wear Resistance ◽  
Rare Earth ◽  
High Temperature ◽  
Eutectic Silicon ◽  
Primary Silicon ◽  
Silicon Phase ◽  
Different Temperatures ◽  
Properties Of Materials ◽  
Re Elements ◽  
Cast Microstructure

In testing comparison, this study is made on the modification effect of 0.05 wt.% La-rich rare earth (RE) upon as-cast microstructure, mechanical properties of materials at high temperatures (100, 150, 200°C) and wear resistance under different temperatures (100and 200°C) of ZA40 alloy containing Si. The addition of RE shows that it can not only effectively refine Al-rich and Cu-rich phase, but also reduce the amount of needle-like eutectic silicon, and then make the size of massive primary silicon phase smaller. Thus, there are the improvement of strength, ductility and wear resistance of materials at high temperature. The analyses are also conducted on the mechanism of underlying RE elements.

Modification of Hypereutectic Al-20%Si Alloy by Neodymium

2015 ◽  
Vol 1095 ◽  
pp. 180-183
Author(s):  
Wei Xi Shi ◽  
Cheng Wu Du ◽  
Guang Zhe Lv ◽  
Chang Wan Liu
Keyword(s):  
Mechanical Properties ◽  
Trace Element ◽  
Base Metal ◽  
Eutectic Silicon ◽  
Trace Element Analysis ◽  
Primary Silicon ◽  
Sem Analysis ◽  
Silicon Phase ◽  
Element Analysis ◽  
Average Grain Size

The modification mechanism was studied by OM, SEM, XRD and Trace Element Analysis. The results of OM and SEM analysis show that pure Nd can effectively refine primary and eutectic silicon in hypereutectic Al-20%Si alloy. Morphology of primary silicon is transformed from pentalpha to block and the average grain size of primary silicon is reduced from 80~120μm to 20~50μm after modification. Trace Element Analysis results show that Nd can purity base metal and reduce impurity contents. XRD patterns show that no new phase formed after Nd modification. The results of mechanical properties test show that whole properties of modified sample are significantly improved. Tensile strength increases about 35.8% from 117 MPa to 148 MPa after modification, Elongation change increases about 193% from 0.56% to 1.64%. The improvement of mechanical properties should be attributed to fine primary Si phase and eutectic silicon phase and purification of base metal after modification.

The Influence of the Al-Ti-B/Al-Sr Modification on the Microstructure and Properties of the Hypereutectic Al-Si Alloy in Automotive Piston

2013 ◽  
Vol 744 ◽  
pp. 339-344 ◽  
Author(s):  
Meng Xiang Liu ◽  
Jian Mei Chen
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Friction And Wear ◽  
Eutectic Silicon ◽  
Primary Silicon ◽  
Optical Microscope ◽  
Sr Modification ◽  
Alloy Microstructure ◽  
Compound Modification ◽  
Better Than

By using some types of means such as Optical Microscope (OM), Scanning Electron Microscopy(SEM), the testing of tensile mechanical properties and the testing of friction and wear, the impacts of the Al-5Ti-1B and Al-20Sr modification on the Al-16Si-4Cu-0.5Mg-0.2Mn alloy microstructure, mechanical properties and friction properties are researched. The results turn out that the modification can significantly refine the primary silicon and the eutectic silicon in the alloy, the Al-5Ti-1B mainly refined the primary silicon in the alloy, the Al-20Sr refined the eutectic silicon; the alloy’s effect of refinement after compound modification is better than that in separate metamorphism. Modification can improve the tensile strength and elongation of the alloy: the tensile strength of the alloy has been increased by 65MPa after its compound modification; also the elongation by 0.4%. Modification can improve wear-resisting property of the alloy and also its effect of compound modification is better than that of separate metamorphism. The modification mechanism of Al-5Ti-1B is that Al3Ti and TiB2 belongs to heterogeneous nucleation; while the modification mechanism of Al-20Sr is that the strontium changes the growth pattern of Si phase.

Effect of Sr + RE Combination Modifier on Microstructure and Mechanical Properties of Al-40 Wt％ Si Alloy

2011 ◽  
Vol 194-196 ◽  
pp. 1296-1300
Author(s):  
Xiao Song Li ◽  
Wei Hu ◽  
An Hui Cai ◽  
Hua Chen ◽  
Yong Zhou
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Uniform Distribution ◽  
Eutectic Silicon ◽  
Primary Silicon ◽  
Large Plate ◽  
Small Block ◽  
Microstructure And Mechanical Properties

The effect of the Sr + RE complex modifications on microstructure and mechanical properties of Al-40 wt% Si alloy were investigated. The results show that Sr + RE complex modification not only on primary silicon and eutectic silicon with modification, but also on dendrite α significantly refine. When the addition of RE remain unchanged, with increasing of the addition of Sr, the primary silicon firstly changes from polygonal block or large plate to small block, then to large polygonal block, edge and corner passivations. The eutectic silicon firstly changes into a fine start with a long needle-like fibrous or branched further to a short stubby dendrite or worm-like, The eutectic silicon changes from needle to a fibrous sheet plus short rod, then to short rod end for the dense, or even granular. The dendrite α changes from highly developed dendritic to equiaxed and uniform distribution. In addition, with increasing of the addition of Sr, the mechanical properties has been significantly improved, tensile strength increased by 37%, elongation is more than double, the hardness increased by 21%. When the Sr addition is between 0.05 wt% and 0.077 wt%, the microstructure and mechanical properties are the best.

Nodular Silicon Al–(12–30)% Si Alloys: Microstructure, Mechanical Properties and Fracture Behaviors

2019 ◽  
Author(s):  
Ruyao Wang ◽  
Wei Hua Lu
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Elevated Temperatures ◽  
Primary Silicon ◽  
Silicon Phase ◽  
Applied Loading ◽  
Initiation And Propagation ◽  
Si Content ◽  
Silicon Particles

The microstructure, mechanical properties, and fracture of nodular silicon hypereutectic Al–Si alloys containing 12–30 wt% Si are discussed. The eutectic and primary silicon particles are nodulized, offering an average aspect ratio of 1.60–1.70 with a designed modification practice followed by a solution heat treatment of 8–10 h at 510°C–520°C. Such a soaking temperature does not result in coarsening or clustering of the silicon particles. Nodulization of silicon phase leads to an increase in the tensile strength and ductility of alloys at room and elevated temperatures compared with commercial Al–Si alloys. Increasing the Si content leads the tensile strength and elongation of alloys at room temperature to fall down due to the formation of coarsen primary Si grains, but the ultimate tensile strength at 300°C remains unchanged. The ultimate tensile strength σb-alloy of hypereutectic Al–Si alloys is inversely proportional to square root of maximum silicon size dmax. The initiation and propagation of the crack with continuous increase in applied loading were observed under scanning electron microscope. The fracture surfaces in nodular silicon Al–Si alloys are composed of equiaxed ductile dimples. The finite-element method has been used to study the stress distribution within the different morphologies of Si grain and how Si and Al phases interact during loading.

Study of the Boron Distribution and Microstructure of Solidified Al-Si Alloy During the Process of Silicon Purification

2018 ◽  
Vol 37 (1) ◽  
pp. 69-73 ◽  
Author(s):  
Yanlei Li ◽  
Jian Chen ◽  
Songyuan Dai
Keyword(s):  
Cooling Rate ◽  
Transition Layer ◽  
Boron Content ◽  
Eutectic Silicon ◽  
Primary Silicon ◽  
Silicon Phase ◽  
Cooling Rates ◽  
Average Width ◽  
Boron Distribution ◽  
Silicon Purification

AbstractThe Al-Si melts that contain different silicon contents were solidified with a series of cooling rates, and the boron contents in primary silicon phases and eutectic silicon phases were measured and discussed. The results indicate that the boron content in the eutectic silicon phases is higher than that in the primary silicon phases when the cooling rate is constant. When the cooling rate decreases, the boron content in the primary silicon phases decreases, but the boron content in the eutectic silicon phases increases. The microstructure observations of solidified ingots show that there is an interface transition layer beside the primary silicon phase, and the average width of the interface transition layer increases with decreasing cooling rate.

Effect of Compound Modification and Cooling Rate on Microstructure and Mechanical Properties of Al-25%Si Alloy

2016 ◽  
Vol 877 ◽  
pp. 27-32
Author(s):  
Hai Tao Zhang ◽  
Dong Tao Wang ◽  
Ke Qin ◽  
Xing Han ◽  
Bo Shao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Mechanical Testing ◽  
Rate Increase ◽  
Eutectic Silicon ◽  
Primary Silicon ◽  
Microstructure And Mechanical Properties ◽  
Phosphorus Modification ◽  
Compound Modification

The effect of phosphorus on primary silicon, phosphorus and mischmetal (Ce-50La) modification on primary and eutectic silicon and cooling rate on microstructure of Al-25%Si are investigated. The results show that, with the addition of phosphorus, the size of primary silicon decreases from 93.6μm to 24.75μm. The morphology of primary silicon changes from irregular to polygonal. When Al-25%Si is modified by phosphorus and mischmetal, primary and eutectic silicon all change effectively. Addition of mischmetal on the basis of phosphorus modification have no influence to primary silicon, but it can make morphology of eutectic silicon change from lamellar to short rod-like when the content of mischmetal reaches 0.5%. The cooling rate curves show the change of temperature in different height of wedge-shaped mould. When cooling rate increases, microstructure of Al-25%Si refines, the size of primary silicon decrease to 22.7μm. The results obtained from mechanical testing demonstrate that the addition of mischmetal and increasing of cooling rate increase hardness value of Al-25%Si alloy.

Effect of Liquid-Die-Forging Pressure on Microstructure and Mechanical Properties of A390 Sloping Swash-Plate

2012 ◽  
Vol 538-541 ◽  
pp. 1356-1359
Author(s):  
Guang An Zhang ◽  
Feng Jiang ◽  
Qi Zhou ◽  
Fu Fa Wu
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Eutectic Silicon ◽  
Applied Pressure ◽  
Primary Silicon ◽  
Specific Pressure ◽  
Die Forging ◽  
Microstructure And Mechanical Properties ◽  
Swash Plate ◽  
Preheating Temperature

The effect of liquid-die-forging pressure on the microstructure and mechanical properties of A390 sloping swash-plate forming was investigated. It was found that the microstructure and comprehensive mechanical properties of the alloy were effectively improved by the liquid-die-forging pressure applied on the A390 aluminum melt. With continuous increasing of the specific pressure, the grain size of primary silicon gradually decreased, the fraction of eutectic silicon obviously decreased, and its morphology was granular mainly. When the applied pressure was 181 MPa, the size of primary silicon was reduced to about 20 μm. When the casting temperature of the alloy was 820 °C, the mould preheating temperature was 240 °C and the forging casting specific pressure reached 181 MPa, the sloping swash plate without macro-defects, and with the internal compact-gain structure and excellent mechanical properties can be obtained.

Microstructure evolution, thermal conductivity and mechanical properties of hot-rolling Al–Si–Fe–Mg alloy under different reductions

2021 ◽  
Author(s):  
Yu Guo ◽  
Ye Wang ◽  
Bo Jiang ◽  
Hongtao Chen ◽  
Hongyu Xu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Hot Rolling ◽  
Eutectic Silicon ◽  
Mg Alloy ◽  
Free Electrons ◽  
Silicon Phase ◽  
Transport Channel ◽  
Overall Performance ◽  
Average Size

To further improve the properties of the Al–11.5Si–0.4Fe–0.35Mg, the effects of different reductions of hot-rolling (HR) Al–Si–Fe–Mg alloy on microstructure, thermal conductivity (TC), and mechanical properties were investigated in this paper. The results show that the eutectic silicon phases are broken and moved during the HR process. The average size of eutectic silicon phase decreases. Meanwhile, the aspect ratio of eutectic silicon phase closer to 1 and the distribution of that are more uniform with the increase of HR reduction. In addition, the ternary Al–Fe–Si phases are also broken after HR. It indicates that the action of shear force induced by the HR process is beneficial to promote refinement and spheroidization of the eutectic silicon phase, hence further improves the properties of the alloy. Apparently, the fine and dispersed distribution of spherical silicon particles can minimize the splitting of the [Formula: see text]-Al matrix, decrease the scattering effect on free electrons, and increase the number of free-electron transport channel. Therefore, the overall performance of HR Al–Si–Fe–Mg alloy with a reduction of 71.25% is the best with the TC of 170.24 W/m[Formula: see text]K, the tensile strength of 241.98 MPa and elongation of 8.73%, respectively.

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.

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