Al-Si Alloy Surface Research Articles

Improvement in Mechanical Properties of AMed Al-Si Alloy Surface by Large-area EB Irradiation

Improvement in Mechanical Properties of AMed Al-Si Alloy Surface by Large-area EB Irradiation

Effect of electron-plasma alloying on structure and mechanical properties of Al-Si alloy

The paper reports on research into element and phase composition, micro-hardness and wear resistance of Al-Si alloy surface layer processed using the method of electron-plasma alloying. When electron-plasma alloying the surface layer of Al conductor is alloyed with Y2O3 powder portion by electric explosion and irradiated by electron beam with different densities of energy. The study has identified important structural transformations in the surface layer of the material irrespectively of electron-plasma alloying mode. The formed layer has a multi-element, multi-phase composition with sub-micro and nanocrystalline structure. Comparison of the modified layer with its primary structure has confirmed dissolution of Si inclusions and micron and submicron intermetallic compounds. The study has revealed a structure of high-speed cellular crystallization in the layer formed in the process of electron-plasma alloying and facetted inclusions, the relative concentration of which drops as far as from the modified surface. A significant drop of micro-hardness in layers has been identified. The findings also point at a sharp decrease in wear parameter in surface layers in comparison with the original state. Assessing transformations of frictional properties, micro-hardness and structure, it is concluded that they are results of nanocrystallization and Y enrichment of surface layers when electron-plasma alloying.

Microstructure Study of the Stainless Steel Layer on AlSi Cast Alloy Prepared by Laser Deposition

The main aim of this study is structural changes on the layer of Al-Si cast alloy by laser austenitic stainless steel 17 246 deposition. In order to remelt the Al-Si alloy surface the laser of 1, 9 kW has been used for facing area, and 1.6 kW for the edge. The linear laser scan rate of the beam was set 450 mm.min-1 for facing area, and for the edge 550 mm.min-1. We observed that the thin surface made of austenitic stainless steel had a lot of splits. The purpose of this study is also to enhance inherent properties of the surface materials to create new product or improve on existing one.

Silicon Addition Influence on Properties of Anodised Al-Si Alloy Surface

Silicon Addition Influence on Properties of Anodised Al-Si Alloy Surface

Improved the elevated temperature mechanical properties of Al-Si alloy deposited with Al-Si coating by magnetron sputtering

Compact and uniform aluminum silicon (Al-Si) coatings with different Si contents were deposited on Al-Si alloy by magnetron sputtering. The structure and mechanical properties of the Al-Si alloy covered with Al-Si coating were characterized. The results indicate that the introduction of Al-Si coating on Al-Si alloy surface can increase the mechanical properties of Al-Si material. Hardness and elastic modulus of the Al-Si coating with 25.2 at % Si reach about 23.6 GPa and 178.0 GPa, respectively, which are obviously higher than those of Al-Si bulk. The Al-Si coating with 25.2 at % Si exhibits the lowest friction coefficient of 0.231 and lowest wear rate of 0.9-1.4 × 10−6 mm3/Nm. The low friction coefficient of Al-Si coating is attributed to the Al and Si debris which react with thermal moisture to form aluminum and silicon oxide, serving as a lubricant between two contact counterparts.

Effect of KrF Pulsed Excimer Laser Treatment on Surface Microstructure of Al-Si Alloy

In the present research, the Al-Si alloy surface is treated by KrF excimer pulse laser for different number of laser pulses in ambient condition at energy 4.75 J/cm2. The surface microstructural characterization was done by the optical microscope, in situ video recording during laser pulsing, SEM and TEM. The fretting wear test was undertaken to assess the tribological behavior. In situ video recording showed changes in the surface reflectivity with the number of pulses which is related to progressive changes in the surface compositional homogeneity. After ten pulses, signs of rippled structure were observed. The 15 pulse samples showed star-like morphological feature at the central region. The TEM observations showed high density of stacking faults/twins in Si after first pulse treatment. After 15 pulses, nano-crystalline Si precipitates in the size range <5 nm are seen to be homogeneously distributed. A cellular structure with the cell size <100 nm formed in the matrix. These cell boundaries were decorated with the Si nanocrystals. A positive effect in wear resistance property is observed after the 15 pulses treatment.

The Corrosion Performance of Al-Si and Al-Cu Casting Alloys in H 2 SO 4 and Na 2 CO 3 Media

This paper focuses on corrosion performance of aluminium-silicon (Al-Si 7 %) and aluminium-copper (Al-Cu 15 %) alloys, produced locally by a casting process, under different conditions of media and temperatures. The selected media are acidic (10 % H2SO4solution) and alkaline (10 % Na2CO3 solution). The corrosion experiments used weight loss and corrosion penetration rate within interval immersion periods of 5 hours. The surface morphology was studied using optical and scanning electron microscopes (SEM). It was observed that, Al-Si 7 % alloy shows less of weight loss and higher corrosion resistance in 10 % H2SO4 and 10 % Na2CO3solutions rather than Al-Cu 15 % alloy at room temperature. The corrosion clearly increased and the attack was more significant at 50 °C. Moreover, corrosion rate values of Al-Si and Al-Cu alloys are higher in H2SO4medium, due to the hydrogen enhancement for the cathodic reaction, than in alkaline medium. This result relates to the formation of Al-Si and Al-Cu oxide surfaces. On the other hand, the surface morphology of the Al-Cu alloy shows that there are clear colored SO42− and CO32− precipitates formed after 5 hours immersion, whereas this behavior does not appear on the Al-Si alloy surface. SEM images show that the corrosion performance increased mainly in the acid medium rather than the alkaline one in which the pores produced on the Al-Si surface may contribute to a decline of sites in the oxide surface.

The dispersive orientated-precipitation of AlP on alumina film and its effect on the primary Si gathering behavior in the Al–Si alloy surface layer

In this paper, the dispersive orientated-precipitation of AlP on γ-Al2O3 film and its effect on the primary Si gathering behavior in the near-eutectic Al–Si alloy surface layer was investigated. Experimental results show that (111) orientated AlP can nucleate on the γ-Al2O3 film, which is attributed to the high tendency for P to be adsorbed on γ-Al2O3 and the good lattice matching relationship between AlP and γ-Al2O3. It was also found that the pre-precipitated AlP particles on the γ-Al2O3 film could induce Si atoms to precipitate into numerous primary Si particles, leading to an extraordinary high volume fraction of primary Si in the near-eutectic Al–Si alloy surface layer. What is more, the X-ray diffraction experiment shows that the intensity of the Si (111) peak increases significantly and other Si peaks decrease to a very low level, which means that the primary Si particles inherited the (111) orientation characteristic from the orientated AlP grains.

Effect of Heat Treatment on Ni-P-C&lt;sub&gt;g&lt;/sub&gt;(Graphite)-SiC Composite Coated Cast AlSi Alloy

The study presents the effect of heat treatment on electroless N-P-Cg-SiC composite coated cast AlSi (ADC12) alloy. No significant changes are noted on the average surface roughness and surface morphology of the coating film with different heat treatment processes. The growth of the hard Ni3P phase in the electroless Ni-P-Cg-SiC composite coating after heat treatment at 400°C for one hour strongly enhance the micro hardness of the AlSi-alloy (ADC12) surface from originally 101HV to 689HV. However, the micro hardness of the cast AlSi-alloy substrate decreases form 100HV to 60HV.

Analysis of Al-Si Alloy Surface Weightlessness after Electron Beam Remelting and Solidification

Al-Si alloy surface is remelting and solidification by electron beam to study the influence of electron beam scan technology on alloy properties.During the electron beam scanning the Al-Si alloy,the phenomenon of surface weightlessness which could affect the surface morphology of the parts and the distribution of the element would exist in the process.The effects of electron beam parameters such as scanning time,scanning frequency and power on the weightlessness of samples after remelting are discussed,theory on gasification differences is also analyzed,the formation conditions of splash is studied,the mechanism of weightlessness formation is disclosed.The experiment results show that weightlessness increases as time and power increase.High frequency block the process of weightlessness,the evaporation capacity of Si whose saturated vapor pressure is lower is more than Al.Under the condition of given parameters,the effective depth of sampling surface comes to 18.5 μm,the highest energy is appeared at 6 μm.The main reason of Al-Si alloy surface weightlessness are the splash of molten pool when the electron beam remelt Al-Si alloy surface and the evaporation of Al phase and Si phase.

D01 Al-Si合金の大面積電子ビーム照射におけるクレータ発生メカニズムの考察(OS8 電気加工(1))

Al-Si alloy has been widely used for engine pistons and cylinders because of its light weight and high wear resistance. It was clarified that the wear resistance could be increased by large-area EB irradiation. However, many craters were generated on the EB irradiated surface. If the crater generation could be reduced, further improvement in wear resistance might be possible. In this study, heat conduction analysis of the Al-Si alloy surface was carried out in order to discuss the temperature distribution and the crater generation mechanism. Then a two-staged large-area EB irradiation method, in which the craters generated by first high energy condition were smoothed by second low energy condition was tried on the basis of the analysis results.

Tribological Properties of Lubricating Films on the Al-Si Alloy Surface via Laser Surface Texturing

Dimpled textures were prepared by using a pulse solid laser on the surface of Al-Si alloy. The combination of laser surface texturing (LST) and MoS2 solid lubricant as well as their tribological properties were investigated in this article. The obtained friction and wear data were critically analyzed to investigate how the parameters of texture influence the tribological performance of Al-Si alloy. Furthermore, morphological investigations of the transfer layers on the worn surfaces were performed and the wear mechanisms are discussed. The results show that the combination of LST and solid lubricant improves the tribological characteristics of Al-Si alloy. The friction coefficient of Al-Si alloy: steel friction pairs can be reduced to 0.15 under dry friction. The lubrication mechanism is attributed to a synergetic effect of providing solid lubricant and traps wear debris in the dimples. It was found that the optimum density of structure was 37% for excellent tribological properties.

The microstructure and tribological characteristics of laser-clad Ni–Cr–Al coatings on aluminium alloy

Using a 5-kW CO 2 laser, a Ni–Cr–Al plasma coating on Al–Si alloy surface was remelted. The microstructure of the clad zone was analysed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that some amorphous structures and crystallites exist in the laser-clad Ni–Cr–Al coating. The annealing treatment was used at 520°C in different time intervals in order to determine the content of amorphous structure in the coating. Wear tests of laser-clad samples paired with grey cast iron were carried out on a block-on-ring wear tester under oil lubricated conditions. The effect of amorphous structure on tribological characteristics of the pairs was investigated. The result showed that the wear amount of laser-clad samples was quite small. The higher the amorphous content, the smaller the wear amount of laser-clad samples and grey cast iron. The amorphous structure can prevent hard granules spalling from the matrix during the wear test and can improve wear resistance.

Segregation phenomena of laser alloyed Ni-Cr-Al coating on Al-Si alloy

A plasma sprayed coating (Ni-Cr-Al) on a Al-Si alloy surface was alloyed by a 5 kW CO2 laser. The chemical composition and the microhardness in the laser alloyed zone were examined. It is shown that compositional segregation appears in the laser alloyed zone. A higher Al content is in the surface of the laser melted zone and higher Ni and Cr content are in the inner of the laser alloyed zone. The segregation appears still in the dendrites and interdendritic areas, Ni is rich in the dendrites and both Si and Cr are rich in the interdendritic areas. Some amorphous structures with high microhardness were found in the bottom of the laser alloyed zone, which caused this region to have higher hardness.

Microstructure and character of laser remelting of plasma sprayed coating (Ni-Cr-B-Si) on Al-Si alloy

In this paper, a plasma sprayed coating (Ni-Cr-B-Si) on an Al-Si alloy surface was remelted by a 5 kW CO 2 laser. Structure and chemical composition of different parts of the laser melted zone were investigated. Hardness distribution in the laser melted zone was measured. Experimental results showed that chemical composition of the sample is not a well-distributed gradient because there is compositional segregation in the laser melted zone. In the surface of the laser-melted zone, a concentration of aluminium exists; and there is a concentration of Fe, Cr and Ni in the sub-surface of this zone. Corresponding to chemical compositional segregation, a aluminium-rich phase Al 3Ni emerges in the surface and the nickel-rich phases AlNi and AlNi 3 are found in the sub-surface. There are some amorphous regions with super-hardness in the sub-surface of the laser-melted zone. Owing to the tempering effect of laser scanning heat transfer, many nano-crystallites of AlNi 3 separate out from the amorphous structure. The hardness distribution in the laser-melted zone corresponds with the structure and solidification conditions. The highest hardness is in the amorphous and nano-crystallite regions. The higher hardness is in the Al + Al 3Ni eutectic structure region that is in the rapidly solidified surface and is in the fine needle-like Al 3Ni 2 structure region that is adjacent to the amorphous region. The thick needle-like Al 3Ni 2 structure has lower hardness.

Formation and crystallization of amorphous structure in the laser-cladding plasma-sprayed coating of Al-Si alloy

An Al-Si alloy surface was plasma sprayed with a Ni-Cr-B-Si coating. This coating was remelted by a 5kW CO2 laser, and the resulting microstructure was characterized by both scanning and transmission electron microscopy. Both crystalline and amorphous structures were observed to coexist in the remelted layer. Heat resulting from laser scanning precipitated some Ni3Al in the amorphous region. A distribution in Ni3Al precipitate size, from nanometer to submicrometer, was observed. Microhardness in the amorphous region measured to HV 1235, which is four times as hard as the untreated plasma-sprayed zone.