Effect of Si content on the microstructure and properties of Al–Si alloys fabricated using hot extrusion

Ma, Peijun; Jia, Yandong; Prashanth, K.G.; Yu, Zhishui; Li, Chonggui; Zhao, Jianwei; Yang, Shanglei; Huang, Lixin

doi:10.1557/jmr.2017.97

Cited by 40 publications

(28 citation statements)

References 37 publications

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“…The eutectic silicon crystallizes under conventional solidification conditions into a course, plate-like morphology. However, under conventional solidification conditions, the Si phase in cast Al–Si alloys often exhibits a coarse microstructure that leads to poor mechanical properties 3 , 5 . When Si content is more than 12%, primary Si particles begin to crystallize as a massive phase with angular morphology which leads to a further reduction in ductility and toughness.…”

Section: Introductionmentioning

confidence: 99%

Developing of nano sized fibrous eutectic silicon in hypereutectic Al–Si alloy by laser remelting

Abboud

Mazumder

2020

Sci Rep

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Laser surface melting followed by rapid solidification is an effective means to produce very fine microstructures with desirable surface properties because of the high rates of cooling associated with it. In the present study, the effect of rapid cooling on the silicon particle size, distribution, and morphology of hypereutectic Al-17wt.%Si and Al-20wt.%Si alloys have been investigated. A continuous-wave CO2 laser of wavelength 10.6 μm and a Trumpf Yb-YAG disk laser of wavelength 1.030 μm were used with a beam diameter of 1 mm and scanning speeds ranging from 5 to 100 mm/s. Rapid solidification increased the solubility of silicon in aluminum to approximately 5wt% and induced non-equilibrium hypoeutectic microstructures comprising large volume fractions of primary α-Al dendrites and ultrafine Al-Si eutectic of lamellar morphology. Both α-Al dendrites and the silicon particle sizes were significantly reduced from micron to nanoscale level. The morphology of silicon particles is modified from massive polygonal and plate-like to a mixture of fine flakes with round corners, feathery and fibrous, or a coral-like and thread-like structure. The eutectic silicon size and the interlamellar spacing were reduced to 30 and 10 nm, respectively. Furthermore, most of the silicon crystals in the eutectic region and the aluminum dendrites contained a significant number of twins which were considered as an essential contributor to the mechanism of growth and branching. Microhardness values increased two to threefold due to the refinement of the microstructural constituent. Al-Si casting alloys have received considerable interest as candidate materials in the automotive and aerospace applications due to the high specific strength, relatively low coefficient of thermal expansion, good wear resistance, and excellent fluidity 1,2. Al-Si alloys used for engine block can be divided into three categories based on their silicon percentage: hypoeutectic (< 12. wt%), eutectic (12 wt% to 12.6 wt%), and hypereutectic (> 12.6 wt%) 1. The microstructure of the hypoeutectic Al-Si cast alloy usually consists of a primary phase (α-Al) and eutectic mixture of Al-Si. The eutectic silicon crystallizes under conventional solidification conditions into a course, plate-like morphology. However, under conventional solidification conditions, the Si phase in cast Al-Si alloys often exhibits a coarse microstructure that leads to poor mechanical properties 3,5. When Si content is more than 12%, primary Si particles begin to crystallize as a massive phase with angular morphology which leads to a further reduction in ductility and toughness. Therefore, to use eutectic and hypereutectic Al-Si alloys in engineering applications, the morphology, shape, and size distribution of the silicon need to be modified and refined. Modification of the Al-Si eutectic has been achieved in different ways such as by the addition of certain elements 6-12 , rapid cooling 13-16,32-34 , heat treatment 17 and by controlling solidification conditions 18. Several modifiers are known (e...

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Section: Introductionmentioning

confidence: 99%

Developing of nano sized fibrous eutectic silicon in hypereutectic Al–Si alloy by laser remelting

Abboud

Mazumder

2020

Sci Rep

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“…The above results indicate that the increase of the Si/C mass ratio is helpful to synthesis of SiC particles. However, when the remaining Si in Al matrix is much more than the eutectic composition (12.6%) after in situ synthesized SiC, the additional Si leads to the rapid reduction of the compactness, strength, and ductility of the sample [ 33 ]. As a result, Si content is about 12% in research on most Al-Si alloy [ 34 – 36 ].…”

Section: Resultsmentioning

confidence: 99%

Fabrication and Characterization of In Situ Synthesized SiC/Al Composites by Combustion Synthesis and Hot Press Consolidation Method

Yang

Dong

Zhang³

et al. 2017

Scanning

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The in situ SiC/Al composites were fabricated in Al-Si-C systems with different Si/C mass ratios and holding time by the method of combustion synthesis and hot press consolidation. The influences of Si/C mass ratio and holding time on the phase constitution, microstructure, and hardness of the composites were investigated. The results indicate that the increase of Si/C mass ratio leads to more uniform size distribution of the SiC particles in the Al matrix. Moreover, by improving the Si/C mass ratio from 4 : 1 to 5 : 1, the maximum size of SiC particle was reduced from 4.1 μm to 2.0 μm. Meanwhile, the percentage of submicroparticles was increased from 22% to 63%, and the average hardness value of the composites was increased by 13%. In addition, when the holding time is set to be fifteen minutes, the Al4C3 phase did not exist in the composites because of its total reactions with Si atoms to form SiC particles, and the average hardness value was 73.8 HB.

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“…This could however reflect the importance of the percentage silicon present in the alloys. Another study by Ma et al [ 10 ] indicated an increase in mechanical strength and a decrease in elongation with Si content from 12 to 35 wt%, [ 10 ]. Their results were characterized by shorter chips due to increased brittle nature of the alloy.…”

Section: Introductionmentioning

confidence: 99%

Investigation on Surface Quality of a Rapidly Solidified Al–50%Si Alloy Component for Deep-Space Applications

et al. 2020

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To meet the requirements for high-performance products, the aerospace industry increasingly needs to assess the behavior of new and advanced materials during manufacturing processes and to ensure they possess adequate machinability, as well as high performance and an extensive lifecycles. Over the years, industrial research works have focused on developing new alloys with an increased thermal conductivity as well as increased strength. High silicon content aluminum (Al–Si) alloys, due to their increased thermal conductivity, low coefficient of thermal expansion, and low density, have been identified as suitable materials for space applications. Some of these applications require the use of intricate parts with tight tolerances and surface integrity. These challenges are often tied to the machining conditions and strategies, as well as to workpiece materials. In this study, experimental milling tests were performed on a rapidly solidified (RS) Al–Si alloy with a prominent silicon content (over 50%) to address challenges linked to material expansion in deep space applications. The tests were performed using a polycrystalline cubic boron nitride (PCBN) tool coated with amorphous diamond to reduce tool wear, material adhesion, surface oxidation, and particle diffusion. The effects of cutting parameters on part surface roughness and microstructure were analyzed. A comparative analysis of the surface with a conventionally utilized Al6061-T6 alloy showed an improvement in surface roughness measurements when using the RS Al–Si alloy. The results indicated that lower cutting speed and feed rate on both conventional and RS Al–Si alloys produced a better surface finish. Reduced vibrations were also identified in the RS Al–Si alloy, which possessed a stable cutting time at low cutting speeds but only displayed notable vibrations at cutting speeds above 120 m/min.

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Effect of Si content on the microstructure and properties of Al–Si alloys fabricated using hot extrusion

Abstract: Abstract

Cited by 40 publications

References 37 publications

Developing of nano sized fibrous eutectic silicon in hypereutectic Al–Si alloy by laser remelting

Developing of nano sized fibrous eutectic silicon in hypereutectic Al–Si alloy by laser remelting

Fabrication and Characterization of In Situ Synthesized SiC/Al Composites by Combustion Synthesis and Hot Press Consolidation Method

Investigation on Surface Quality of a Rapidly Solidified Al–50%Si Alloy Component for Deep-Space Applications

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