Microstructure and properties of Al-60wt.%Si composites prepared by powder semi-solid squeeze

Accepted Manuscript Microstructure and properties of Al-60wt.%Si composites prepared by powder semi-solid squeeze

Junwu Liu, Daochuan Jiang, Xingxing Zhou, Yonghong Wang, Xuemin Liu, Hongxing Xin, Yang Jiang, Lei Yang, Yujun Zhang, Zhigang Huang, Dong Feng PII: DOI: Reference:

S0032-5910(18)30915-X https://doi.org/10.1016/j.powtec.2018.11.011 PTEC 13846

To appear in:

Powder Technology

Received date: Revised date: Accepted date:

10 January 2018 17 October 2018 2 November 2018

Please cite this article as: Junwu Liu, Daochuan Jiang, Xingxing Zhou, Yonghong Wang, Xuemin Liu, Hongxing Xin, Yang Jiang, Lei Yang, Yujun Zhang, Zhigang Huang, Dong Feng , Microstructure and properties of Al-60wt.%Si composites prepared by powder semi-solid squeeze. Ptec (2018), https://doi.org/10.1016/j.powtec.2018.11.011

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ACCEPTED MANUSCRIPT Microstructure and properties of Al-60wt.%Si composites prepared by powder semi-solid squeeze Junwu Liua* , Daochuan Jianga, Xingxing Zhoua, Yonghong Wanga, Xuemin Liua, Hongxing Xinb* , Yang Jianga, Lei Yangc, Yujun Zhangc, Zhigang Huangc, Dong Fengc

School of Materials Science and Engineering, Hefei University of Technology, Hefei,

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a

China b

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Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese

c

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Academy of Sciences, Hefei, China

43 Institute, China Electronics Technology Group Corporation, Hefei, China

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Correspondence information:

1. Junwu Liua*, e-mail: [email protected]; 086-13955107752

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2. Hongxing Xinb*, e-mail: [email protected]

ACCEPTED MANUSCRIPT Abstract Al-60wt.%Si composites were successfully prepared by semi- solid squeezing powder mixture of Al and Si at 700 ℃. The appearance of about 50wt.% Al-Si metal liquid results that less than 4-5 MPa pressure can squeeze the Al-Si powder mixture to near full density at vacuum condition. The effects of Si particle size on the microstructure

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and properties of Al-60wt.%Si were investigated. The results show that the composites are consisted of only Si and Al. Si particles distribute evenly in aluminum

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matrix. Al matrix exhibits a certain preferred orientation under the condition of directional solidification. Si particles with 5 μm size tend to be aggregated into locally

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interconnected particles and can be effectively passivated. As Si particle size ranges from 10 to 20μm, the corner passivation effect for Si particles is gradually suppressed.

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The fracture morphology of Al-60wt.%Si is composed of cleavage platforms of Si grains and fine tearing ridges of Al which tightly wraps Si grains. With the increase of

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Si particle size from 5 to 20μm, the flexural strength of Al-60wt.%Si decreases from 270MPa to 223MPa, the thermal conductivity increase from 128 to 136 W·m-1 ·℃-1 ,

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and the average coefficient of thermal expansion from ambient temperature to 400 ℃ ranges from 9.49 to 9.97×10-6 ℃-1 .

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Keywords: powder semi- solid squeeze; particle size; Al-Si composites; passivation;

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flexural strength; thermal conductivity

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1. Introduction Ceramic particles reinforced metal matrix composites are not only isotropic in performance, but also can be produced by relatively simple process. Nowadays, research results show that ceramic particles reinforced aluminum metal matrix

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composites exhibit a combination of superior physical and mechanical performance, which leads them wide application in spacecrafts, automobiles, and electronic

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components as structural or electronic packaging materials [1-4]. High volume

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fraction ceramic particles with high thermal conductivity reinforced aluminum matrix composites not only have higher specific strength and elastic modulus, but also have

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lower coefficient of thermal expansion (CTE) and higher thermal conductivity (TC), which made them particularly suitable for use as heat dissipation materials in light

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weight microelectronics packaging [5-8]. In this respect, High volume fraction SiC, Diamond and Si reinforced aluminum matrix composites (signed as H-SiC/Al, H-Cd/Al, H-Si/Al, respectively) have achieved remarkable success [1, 9, 10].

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Compared with the high strength ceramic reinforced aluminum matrix composites，such as the most widely used H-SiC/Al, H-Si/Al has a distinct difference

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whether in preparation process or performance characteristics [10-14]. Liquid metal infiltration processes, including gas pressure or mechanical pressure infiltration, is the

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mainstream technologies for these high strength ceramic particles reinforced aluminum matrix composites [15, 16]. In these processes, the combination of coarse and fine particles must be adopted to improve the ceramic volume content to beyond 60% [17, 18]. Although the particle size of the coarse one usually reaches 50-70 μm, the obtained composites still have sufficient flexure strength, usually beyond 300 MPa, to meet the requirements for precision machining [17, 19]. However, silicon is a kind of brittle ceramic with lower strength. When similar combination proposal of coarse and fine particles used for H-Si/Al fabricated also by infiltration process, the resulting strength of the composites is only 100-200 MPa [20, 21], which cannot meet the highly reliable requirements of precision machining. Si particles are obtained usually

ACCEPTED MANUSCRIPT by mechanical crushing method, lots of sharp edges and corners exist in coarse Si particles [20, 21]. When conventional pressure infiltration technology is adopted to prepare H-Si/Al composites, the coexistence time of solid silicon particles and liquid aluminum is very short, little solution of Si into liquid Al cannot change the shape of silicon particles. The sharp corners of the Si particles remained tend to cause high

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stress concentration, resulting in insufficient overall strength of the composite [20-23]. For H-Si/Al composites, the main problem is to find a proper fabrication process to

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obtain fine or coarse silicon particles with passivated corners in the final composites. By this way, stress concentration can be effectively depressed, resulting in the

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improvement of strength of the material to meet the application requirements. Metallurgy hot pressing technology, such as hot isostatic pressing (HIP),

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mechanical hot pressing or extruding, applied on Al-Si spray deposition billets or Al-Si mixed powder is an effective way to reach full density for H-Si/Al composites

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[24-26]. Through maintaining pressure on the solid state Al-Si preforms for a long time, not only the densification can be achieved, but also the ideal particle

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morphology of passivated silicon particles can be obtained through the solid state diffusion of Si or Al in the billets [27-29]. But these processes all need costive

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equipments and the macrocracks easily appear under high pressure during the hot press densification operation, especially for H-Si/Al with Si content beyond 60%. This article presents a novel method, called as powder semi-solid squeeze, to fabricate

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H-Si/Al with 60 wt.%Si mass fraction (signed as Al-60Si) from fine powder mixture of Al and Si. At the squeeze temperature beyond the melt point of Al, very low pressure is needed to squeeze the dispersed droplets of Al alloy into the space among nearby Si particles to achieve a compact Al-60Si block. Very low densification pressure not only makes the preparation of H-Si/Al more convenient, but also greatly reduces the manufacturing cost. The coarsening and sharp corner passivating phenomenon for Si particles in semi-solid squeezing process are investigated. The structure and performance of the squeezed Al-60Si composites were also examined.

2. Experimental methods

ACCEPTED MANUSCRIPT Three particles sizes of Si powder (5, 10 and 20 μm respectively, 99.9% purity) and Al powder (10μm, 99.85% purity) were used as starting materials. According to 60% Si mass ratio in Al-Si powder mixture, each particles size of Si powder was mixed evenly with Al powder to get three groups Al-60Si mixtures, correspondingly noted as Al-5μSi, Al-10μSi and Al-20μSi, respectively. After pre-pressing on manual

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hydraulic press, powder semi-solid squeeze of Al-60Si powder mixture was carried out in the vacuum hot press device developed by author. The device for powder

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semi-solid squeezing is shown in Fig. 1. The device was composed of an upper punch, a bottom punch, a mould to hold the powder mixture of Al and Si, a support plate and

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a backing plate. Auxiliary devices include resistance heater, thermal insulator, vacuum pressurized equipment and water-cooling system, etc. The squeezing

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temperature was controlled at 700 ℃, and the pressure was maintained at 4-5 MPa for 30 minutes. According to Al-Si binary phase diagram, Si concentration in Al-Si

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saturated solution at 700 ℃ is about 20%. Thus, the mass fraction of liquid Al-Si alloy in mixture can be calculated out to be about 50%, which results that Al-Si mixed

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powder has been converted into the porous slurry with about 50% Al-Si liquid phase, and these pores can be removed by applying 4-5 MPa pressure at vacuum condition to

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obtain dense Al-Si semi-solid slurry. The pressure needed in this method is only about one tenth of the pressure used in the conventional hot densification methods, such as HIP and hot pressing [10, 24-26]. Accompanying the cooling process of the furnace at

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a speed of 2-5 ℃/min, water passed continuously through the cool-device to speed the cooling the sample from the bottom. Fig.2 is the section of Al-60Si sample prepared by powder semi-solid squeeze. The microstructure and performance tests for Al-60Si were carried out after annealing at 390 ℃ for 3 hours. The particles size distributions of Al and Si as received were analyzed on Mastersizer 2000 and the morphology and distribution of the Si grains were investigated by MR2000 optical microscopy. The particle morphology of raw materials and fracture morphology of the achieved composites were observed by scanning electron microscopy (FE-SEM, Sigma, Zeiss). XRD analysis was carried out on D/MAX 2500V X-ray diffractometer using CuKα radiation. Three-point flexural

ACCEPTED MANUSCRIPT strength test was carried out on DCS-5000 universal electron testing instrument. CTE was examined on a DIL 402C Dilatometer. Coefficient of thermal diffusion (CTD) was measured by LFA457 laser thermal diffusion instrument at ambient temperature. Thermal conductivity (TC) can be calculated according to the following formula: λ =α·Cp ·ρ

(1)

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Where α, Cp , ρ and λ are thermal diffusion coefficient, specific heat, density and TC for the composites, respectively. The densities of the composites were measured

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by Archimedes’ principle.

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3. Results and discussion 3.1. Materials as received

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The typical morphologies of the two kinds of powders as received are shown in Fig. 3. Si particles (Fig. 3(a), (b) and (c)) are obtained by mechanical crush. The sharp

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edges and corners of the Si particles were formed by the intersection of the cleavage planes in different directions, which may lead stress concentration in the final H-Si/Al composites. Al powder (Fig. 3(d)) is prepared by nitrogen atomization, and its shape

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is nearly spherical or dumbbell-shaped. The particle size distributions of Si and Al powders as-received are shown in Fig.

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4. The peak locations of the particle size distributions for various powders are close to their corresponding nominal particle sizes. The particle size distribution of Al powder

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partially overlaps the particle size distributions of the three groups of Si powders. Little differences in density and particle sizes between Si and Al are beneficial to improve the uniformity of the Al-Si powder mixture. 3.2. XRD analysis

Fig. 5 shows the XRD patterns of the Al-60Si samples, indicating that the composite prepared by powder semi-solid squeeze was only comprised of only two phases of Si and Al. No reaction compound, such as oxide, was found, which indicates that there were no appreciable oxidation of Si or Al happens during the process. High purity of the original materials of Si and Al maintained is beneficial for performance, especially for TC.

ACCEPTED MANUSCRIPT The lattice constants obtained from XRD patterns of Al-60Si composites shows that there is no perceptible change in lattice constants of Al or Si for the different Al-60Si samples, which suggests that Si atoms precipitate completely from aluminum matrix. However, the diffraction intensity of Al(111) is weakened with the decreasing of powder size of Si in the Al-60Si samples. Since the bottom of the sample is cooled by water, it is possible that there are the preferred orientations of Al in the Al-60Si

I relative 

)

 I ( 220

)

 I ( 311 )  I ( 222

I hkl I ( 111 )  I ( 200

)

 I ( 220

)

 I ( 311 )  I ( 222

]

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Al

)

sample

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Fc

(1)

a r d

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[

I hkl I ( 111 )  I ( 200

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[

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samples. The relative intensity of diffraction peak was defined as [30]:

In the formula, the intensity of Al PDF Card is adopted from standard card No.

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00-004-0787, and the relative intensities of calculated XRD at various planes for Al phase in the Al-60Si composites are listed in Table 1. Depended on the relative

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intensity, the preferred orientation of each plane for Al phase can be roughly confirmed [30]. The (111) plane of Al phase for the sample of Al-20μSi exhibited a

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relative intensity of 1.00, whereas the relative intensity of (200), (220), (311), and (222) planes is 0.55, 0.46, 2.44, and 0.86, respectively. It suggests that the grain

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grows along the preferred orientation of (311) plane in the Al phase. In the sample of Al-10μSi, the relative intensity of (111), (200), and (220) planes is lower than 1, whereas (311) plane shows a higher relative intensity of 2.21, and the relative

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intensity of (222) plane is 1.29. Therefore, the grain grows still along the preferred orientation of (311) plane when the Aluminum phase is solidified. However, in the sample of 1 Al-5μSi, (220) plane shows a higher relative intensity of 3.57, and the relative intensity of other planes is lower than 1. It means that the preferred orientation of the Al grain changes to (220) plane. It can be seen that the brightness area of Al surrounded by dark area of Si becomes gradually smaller when the size of Si powder becomes smaller from Fig. 6. Based on the results, it can be concluded that the preferred orientation of Al phase exhibits in the matrix alloy changes from the grain plane (311) to (220) when the grain growth space is limited to a certain size. 3.3. Microstructure

ACCEPTED MANUSCRIPT Fig. 6 shows the metallographic structures of directional solidified Al-Si slurry with different particle size of Si powder used as raw materials. The dark region is for Si phase and the bright area is for Al phase. In which no pore or micro-crack was found，indicating the three groups of Al-60Si composites are all nearly full dense. Si particles distribute evenly in aluminum matrix. Although the dissolution of Si in the

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liquid aluminum reaches hypereutectic, there is no Al-Si lamellar eutectic in solidified Al-Si billet can be observed, showing that Si dissolved in the Al liquid can precipitate

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easily on the surface of undissolved solid Si particles during the sample cooling down, replacing spontaneously nucleating and growing in the aluminum liquid [7, 22, 31].

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As Si particle size increases from 5 μm to 20μm, the particle sizes of Si grains in the final Al-60Si composites, just as shown in Fig. 6, increase gradually. When Si

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particle size is 5 μm, Si particles in the composites tend to be aggregated into locally interconnected particles with twisted contours, just as shown in Fig. 6(a). Fig. 6(d) is

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the enlarged view of area signed by dotted line in the upper right corner of Fig. 6(a). In Fig. 6(d), no sharp edges and corners in the mutual-connected Si particles can be

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observed, and the morphology of Si grains in Al-5μSi is basically the same as that of spray formed H-Si/Al [32, 33]. When Si particle size increases from 10μm to 20μm,

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Si particles in the composites tend to exist in discrete states with slight mutual bonding, showing as Fig. 6(b) and (c). The sizes of polymerized Si particles signed by arrows in Fig. 6(b) and (c) occasionally reach near 50μm. The contours of the Si

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particles in the composite prepared from 20μm Si are much sharper than that prepared from 10μm Si, and the morphology of Si grains in Al-20μSi tends to be consistent with that of H-Si/Al prepared by infiltration technology or SPS [20-22]. The above- mentioned morphological evolution of Si particles indicates that the more coarse Si particles can lead to the more difficult in passivation during the powder semi-solid squeeze process. 3.4. Flexural strength The flexural strength of Al-60Si composites with different Si particles sizes are listed Table 2. W ith the increase of Si particle size from 5 to 20 μm, the flexural strength of Al-60Si composites decreases from 270MPa to 223 MPa gradually,

ACCEPTED MANUSCRIPT showing that, when Si content is the same, the strength of H-Si/Al is significantly affected by the size and shape of the Si particles [10, 34, 35]. Si particles with larger sizes and sharper edges or corners may lead greater stress concentration in H-Si/Al. Therefore, it is important to control the particle size and shape of Si in the process of preparing H-Si/Al. For comparison, the flexural strength of Al-60Si composites

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prepared by other methods is listed in Table 2, and the raw materials used in corresponding technology are also signed in the Table. It can be found that although

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the particle size of the coarse Si particles derived by aggregation in Al-60Si fabricated by powder semi-solid squeeze is slightly larger than that of the coarse Si particles in

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the Al-60Si prepared by vacuum pressure infiltration [20] and SPS [21], the flexural strengths of the H-Si/Al prepared by powder semi-solid squeeze are still much higher

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than that of H-Si/Al fabricated by SPS and vacuum pressure infiltration. This may be due to the full contact and wetting between liquid Al and solid Si particles during the

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powder semi-solid squeezing, which makes the Al-60Si composites have higher Al-Si interface bonding strength.

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3.5. SEM

The macro- fracture surfaces of Al-60Si are all straight, indicating that brittle

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fracture of Si powder plays a dominant role in the composites. The micro- fracture morphologies of the three groups of Al-60Si are presented in Fig. 7. Lots of fine cleavage platforms deriving from the fracture of Si grains can be observed. The size

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of cleavage platform of Si grain increases with the particle size of Si powder as received, just as shown in Fig. 7(a), (b) and (c). Fine tearing ridges of Al which tightly wraps Si grains can be observed, meaning that matrix Al experiences plastic deformation before the fracture. The crack does not preferentially extend along the Si-Al interface, but passes indiscriminately through the coarse or fine Si grains, indicating that the Si- Al interface of H-Si/Al prepared by powder semi- solid squeeze is well bonded, which is beneficial to the improvement of the strength and thermal conductivity of the composites. 3.6. Thermal properties Fig. 8 shows the CTE of powder semi-solid squeezed Al-60Si. The average CTEs

ACCEPTED MANUSCRIPT of the prepared Al-50Si from ambient temperature to 400 ℃ are 9.49-9.97×10-6 ℃-1 . It can be seen that the CTEs of the three groups of Al-60Si all increase with the increase of the temperature till 300 ℃, and then decrease gradually. For a single Al or Si, the CTE is monotonically increasing with temperature [36]; so theoretically, the CTE of the Al-Si compounds should also be monotonically increasing with temperature.

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Inflection points appear in the Fig. 7 may be due to the solid solution of Si into the adjacent Al matrix at high temperature [37, 38]. The CTE slightly increases with the

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coarseness of the raw material Si. This is may be due to the finer size of the Si particles, the more dispersed distribution of Si in the Al matrix, and leading the

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stronger the restraining ability of Si to the Al matrix.

The coefficient of thermal diffusivity (CTD) and TC of powder semi-solid

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squeezed Al-60Si at room temperature are shown in Fig. 9. As the particle size of Si increases from 5 to 20 μm, the CTD and TC of Al-60Si composites increase from

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0.66 cm2 · Sec-1 and 128 W·m-1 ·℃-1 to 0.69 cm2 · Sec-1 and 136 W·m-1 ·℃-1 gradually. The TC of Al-60wt.%Si composites provided by Sandvik Osprey, which is signed as

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CE9F, is about 121 W·m-1 ·℃-1 at 25 ℃[39, 40]. Experimental data indicate the thermal conduction properties of the three groups of Al-60Si prepared by powder

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semi-solid squeeze are all higher than that of CE9F. The thermal conductivities of single crystal Si and Al were 148 W·m-1 ·℃-1 and 237 W·m-1 ·℃-1 [41], respectively. The TC of composite materials depends not only on the respective TC of the matrix

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and the reinforcement, but also on the thermal interface resistance between the two constituents [42, 43]. In the case that components and their contents are the same, although the thermal interface resistance per unit area is also the same, the finer Si particles means that the more dispersed Si particles in the Al matrix, the larger the interfacial area in the composite and the corresponding higher total interfacial thermal resistance, which leads the overall TC of the Al-Si composite decreases.

4. Conclusions Al-60wt.%Si composites were successfully prepared by semi-solid squeezing powder mixture of Al and Si at 700 ℃. The mass fraction of liquid Al-Si alloy in

ACCEPTED MANUSCRIPT mixture may reach about 50%, which results that less than 4-5 MPa pressure can squeeze the Al-Si slurry to near full density at vacuum condition. XRD analysis shows that the composites are consisted of only Si and Al. Si particles distribute evenly in the aluminum matrix. The X-ray diffraction pattern of composites testified that when the particle size of Si powder decrease to a certain size, the Al matrix exhibits a certain preferred orientation during the directional solidification. Si

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particles with 5 μm size tend to be aggregated into locally interconnected particles,

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and sharp corners of the Si powder can be effectively passivated. As the Si particle size increases further from 10 to 20, the corner passivation effect for Si powder is

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gradually suppressed. The microscopic fracture morphology of Al-60wt.%Si is comprised of cleavage platforms deriving from Si grains and Fine tearing ridges of Al

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which tightly wraps Si grains. Al-60wt.%Si prepared by powder semi-solid squeeze have excellent mechanical and thermo-physical properties. With the increase of Si

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particle size from 5 to 20μm, the flexural strength of Al-60wt.%Si decreases from 270MPa to 223MPa, the thermal conductivity increase from 128 to 136 W·m-1 ·℃-1 ,

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and the average CTE from ambient temperature to 400 ℃ ranges from 9.49 to

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9.97×10-6 ℃-1 .

Acknowledgements

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This work was supported the Key Research and Development Project of Anhui Province of China (Grant No. 1704a0902023).

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high volume- fraction SiCp-Al-based composites. Metall. Mater. Trans. A Phys.

[35] C. W. Nan, D. R. Clarke, The influence of particle size and particle fracture on

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the elastic/plastic deformation of metal matrix composites. Acta Mater. 44 (1996) 3801-3811.

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[36] Y. Okada, Y. Tokumaru, Precise determination of lattice parameter and thermal expansion coefficient of silicon between 300 and 500K, J. Appl. Phys. 56 (1984)

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314-320.

[37] T. A. Hahn, R. W. Armstrong. Internal stress and solid solubility effects on the

179-193.

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thermal expansivity of Al-Si eutectic alloys Int. J. Thermophys. 9 (1988)

[38] Q. Zhang, G. Wu, L. Jiang, G. Chen. Thermal expansion and dimensional

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stability of Al-Si matrix composite reinforced with high content SiC. Mater. Chem. Phys. 82 (2003) 780-785. [39] Sandvik Osprey Ltd, http://www.cealloys.com/TechPapers.html. (2017). [40] Sandvik Osprey Ltd, http://www.cealloys.co.uk/. (2017). [41] C. Vincent, J.F. Silvain, J.M. Heintz, N. Chandra, Effect of porosity on the thermal conductivity of copper processed by powder metallurgy, J. Phys. Chem. Solids, 73 (2012) 499-504. [42] D. P. Hasselman, L. F. Johnson, Effective thermal conductivity of composites with interfacial thermal barrier resistance. J. Compos. Mater. 21 (1987) 1011-1013.

ACCEPTED MANUSCRIPT [43] W. L. Zhang, D. Y. Ding, P. Gao, High volume fraction Si particle-reinforced aluminium matrix composites fabricated by a filtration squeeze casting route.

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Mater. Design 90 (2016) 834-838.

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Figures and captions:

Fig. 1. Schematic diagram of semi solid squeezing for powder mixture of Al and Si

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1-upper punch; 2-cavity die; 3- powder mixture of Al and Si; 4-thermocouple;

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5-bottom punch; 6-support plate; 7-backing plate; 8-water cooling plate; 9-sealed shell; 10-heating jacket; 11-sulating cover; 12- vacuum gauge port; 13-squeezing rod;

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14-vacuum pump port

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Fig. 2. Section of Al-60Si prepared by powder semi-solid squeeze

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(a)

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(d)

20 µm

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Fig. 3. Typical morphologies of the powders as received (a) 5μm Si, (b) 10μm Si, (c) 20μm Si, (d) 10μm Al

20 µm

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Si-5μm Si-10μm Si-20μm Al-10μm

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Volume (%)

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0 0.1

1

10

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1000

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Particle size (μm)

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Fig. 4. Particle size distributions of Si and Al as received

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Fig. 5. XRD patterns of Al-60Si

Si (422)

Si (331) Al (311） Al (222）

Si (400)

Al (220）

Si (311)

Al (200) Si (220)

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20 Al (111）

Si (111)

Intensity /a.u.

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c- Al-20Si b- Al-10Si a- Al-5Si

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Fig. 6. Optical micrographs of powder semi-solid squeezed Al-60Si composites

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(a) Al-5μSi, (b) Al-10μSi, (c) Al-20μSi

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Fig. 7. Fracture surfaces of semi-solid squeezed Al-60Si

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(a) Al-5μSi, (b) Al-10μSi, (c) Al-20μSi

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Al-20Si

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Al-5Si

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CTE /10-6℃-1

Al-10Si

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Fig. 8. CTE of powder semi-solid squeezed Al-60Si

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α/cm2.Sec-1

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λ/W.m-1.℃-1

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Fig. 9. CTD and TC of powder semi-solid squeezed Al-60Si

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Table 1 The relative XRD diffraction intensity of different plane for Al phase in Al-60Si (111)

(200)

(220)

(311)

(222)

Al-20μSi

1.00

0.55

0.46

2.44

0.86

Al-10μSi

0.89

0.69

0.77

2.21

1.29

Al-5μSi

0.75

0.51

3.57

0.80

0.41

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Sample

ACCEPTED MANUSCRIPT Table 2 Flexural strength of the H-Si/Al composites fabricated by various methods Flexural strength/MPa

starting materials

Manufacturing Technology

60wt.%

270 259

10 μm Al +5 μm Si 10 μm Al + 10 μm Si

powder semi-solid squeeze

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10 μm Al + 20 μm Si

60 wt.%

130～170

10, 28 and 50 μm Si + Al cast

vacuum pressure infiltration [20]

60 wt.%

～200

10 μm Al and 44 μm Si

SPS [21]

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Si content

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ACCEPTED MANUSCRIPT Highlights 

A low cost methods to prepare Al-60wt.%Si near full density was proven feasible.

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Effect of Si particle size on the morphology of Si grains was investigated.

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The effect of Si grain size and the morphology on the properties was obtained.

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Al-60wt.%Si prepared by powder semi-solid squeeze have excellent

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properties.