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Evaluate the Effects of Various Surface Roughness on the Tribological Characteristics under Dry and Lubricated Conditions for Al-Si Alloy

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Journal of Surface Engineered Materials and Advanced Technology 2012年第3期2卷 167-173页

作者： Riyadh A. Al-Samarai Haftirman Khairel Rafezi Ahmad Y. Al-Douri Institute of Nano Electronic Engineering University Malaysia Perlis Kangar Malaysia. School of Materials Engineering University Malaysia Perlis Arau Malaysia School of Mechatronic Engineering University Malaysia Perlis Ulu Pau Malaysia

The effect of surface roughness average of hypereutectic aluminum silicon alloys (with 16 wt% Si) on the friction and wear was investigated. Various surface roughness average (Ra) of different degrees was verified as well as three different loads 10, 20 and 30 N, speeds 200, 300 and 400 rpm and relative humidity 77%. Different surface preparation techniques are resulted in different Ra values from (6, 8 and 12) ± 0.05 μm. The contacts were dried sliding and lubricated regime at 2.5 centimeters per second. Surfaces were analyzed with scanning electron microscopy and X-ray dispersive analyses. It was noted that the weighted and volumetric wear rate decreases as degree of roughness decreases, as well as coefficient of friction is considered as a function of the stability state. Wear rate is decreased and the transition stress from high to low wear is increased with increasing surface roughness average. There was a correlation between friction coefficient and hardness.

关键词： aluminum-silicon Alloy Boundary Lubrication Casting Surface Roughness Adhesive Wear

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Hot Forging and Hot Pressing of AlSi Powder Compared to Conventional Powder Metallurgy Route

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Materials Sciences and Applications 2011年第8期2卷 1127-1133页

作者： Sayed Moustafa Walid Daoush Ahmed Ibrahim Erich Neubaur 不详

aluminum silicon alloy of composition (Al-25%Si-3%Ni-1%Fe-2%Cu) was atomized using water atomization. The powders were cold compacted in a die to produce green cylinder compacts. Four consolidation processes were applied, namely;conventional sintering at 500℃, sintering followed by hot forging to obtain pistons, one step hot forging into pistons, and hot pressing. The microstructure of the sintered specimens showed inter-granular pores and oxide layers on particle interfaces of 84% relative density. When the sintered specimens were hot forged, both the inter-granular pores and oxide layers on particle interfaces almost disappeared and the relative densities increased up to about 95%. The same microstructure is also obtained for the one step forged specimens, but the relative densities increased to about 97%. However, the hot pressing specimens showed the presence of oxide layers on particle surfaces as well as few isolated pores. The relative density of the hot pressed specimens was about 90%. Hardness and ultimate compression strength were measured. It is noted that the strongest bulk materials are those made by hot forging, followed by those made by hot pressing and the weakest bulk materials are those made by conventional sintering.

关键词： aluminum-silicon Alloy Powder Metallurgy Hot Forging Hot Pressing Hardness Compression Test

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Structural Modification of Sand Cast Eutectic Al-Si Alloys with Sulfur/Sodium and Its Effect on Mechanical Properties

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World Journal of Engineering and Technology 2013年第2期1卷 9-16页

作者： Chikezie W. Onyia Boniface A. Okorie Simeon I. Neife Camillus S. Obayi Department of Metallurgical & Materials Engineering Enugu State University of Science and Technology Enugu Nigeria Department of Metallurgical & Materials Engineering University of Nigeria Nsukka Nigeri Department of Metallurgical & Materials Engineering University of Nigeria Nsukka Nigeria Department of Metallurgical & Materials Engineering University of Nigeria Nsukka Nigeria.

In the present study, the structural modification of sand cast Al-12wt%Si alloy with sulfur/sodium and its effect on mechanical properties were investigated. Different addition levels of sulfur and sodium were used to modify and produce castings of the same shape and size from the alloy. The results indicated that the addition of sodium or sulfur to eutectic Al-Si alloy can modify the Al-Si eutectic morphology from needle-like eutectic silicon structure to fine-scale eutectic silicon structure with significant improvement in mechanical properties of the alloy. The optimum levels of modification by sodium flux (60% NaF and 40% NaCl) and sulfur were found to be 0.6% - 1.0% and 0.02% - 0.05% of the weight of the alloy respectively. The alloy modified with 0.6% Na flux had the best mechanical properties closely followed by the one modified with 0.02% sulfur. Over modification of the alloy with sodium produced over modification band which consisted of aluminum dendrites and coarse silicon particles in the microstructure of the alloy. Increase in concentration of sulfur decreased the degree of fineness of the eutectic silicon structure with significant decrease in mechanical properties of the alloy and this is suggested to be as a result of the presence of a brittle sulfur compound at the grain interfaces of the alloy.

关键词： aluminum-silicon Alloy Sand Casting Modification Morphology Mechanical Properties

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