32 research outputs found
A Comparative Study on Microstructure and Tensile Properties of Spray Formed and Ascast Al-28Si-5Cu-4Fe and Al-28Si-5Cu-4Mg Alloys
In the present study, Al-28Si, Al-28Si-5Cu-4Fe and
Al-28Si-5Cu-4Mg alloys were produced by spray forming and
subsequently hot pressed for densiļ¬cation. The effect of alloy composition on the microstructure and mechanical behavior of spray-formed alloys were investigated. The microstructures consist of an equiaxed, nearly spheroidized grain morphology of Ī±-Al matrix. The spray formed alloys exhibited sharply decreased segregation and increased metastable solid solubility and greater volume fraction of Si particles and intermetallic phases. Spray formed Al-28Si-5Cu-4Fe alloy contains Al 2 Cu,
Al 5 FeSi along with Si. On the other hand, Al-28Si-5Cu-4Mg
alloy showed Al 2 Cu, Al 48 Si 29 Mg 18 and Si. Hot pressing lead to
a signiļ¬cant reduction of porosity and partial recrystallization
of spray formed alloys. The room temperature tensile tests of
spray formed hot pressed alloys showed signiļ¬cant increase
in ultimate tensile strength compared to as cast alloys. Spray
formed hot pressed Al-28Si-5Cu-4Fe alloy exhibited superior
ultimate tensile strength and signiļ¬cant increase in elongation to
fracture. This may be attributed to the presence of homogeneous
distribution of ļ¬ne Si particles, high content of short needle-like
Ī²-Al 5 FeSi intermetallic and precipitation strengthening phases
Effect of Cu and Mg on the wear properties of spray formed Al -22Si alloy
In the present study, the effect of Cu and Mg on the wear behavior of spray formed
Al-22Si alloy has been investigated and the same has been compared with that of its counterpart
as-cast alloy. Al-22Si and Alā22Siā4Cuā1.7Mg alloys prepared by spray deposition process
were hot pressed to reduce the porosity. The microstructures were examined by optical and
scanning electron microscopes. The microstructure of spray formed Al-22Si alloy is fine and
homogeneous and primary silicon phase distributed in the aluminum matrix evenly are fine and
faceted having a mean size of 12 Āµm. The microstructure of spray formed Alā22Siā4Cuā1.7Mg
alloy exhibited equiaxed grain morphology with fine and uniform distribution of both primary
and eutectic Si with fine Q-Al-Si-Mg-Cu phase and Īø-Al 2 Cu precipitates dispersed evenly in Ī±-
Al matrix. In contrast the microstructure of as-cast Alā22Si alloy consisted of coarse plates of
primary Si of size 350 Āµm and eutectic Si needles. The as-cast Alā22Siā4Cuā1.7Mg alloy
consisted of coarse primary Si with Chinese script like Īø-Al 2 Cu precipitates and needles of Q-Al-
Si-Mg-Cu phase in Ī±-Al matrix. The wear study of both as-cast and spray formed and hot
pressed alloys under an applied load of 10 to 50 N and sliding velocity of 0.4 to1.5 ms -1 indicated
two distinct regimes of mild and severe wear. In both the regimes, the spray-formed and hot
pressed alloys consistently indicated a low wear rate compared to that of as-cast alloys. The high
wear resistance of spray formed and hot pressed Alā22Si and Alā22Siā4Cuā1.7Mg alloys were
explained in the light of their microstructural modifications induced during spray forming and
subsequent hot pressing
Effect of Atomization Parameters on Size and Morphology of Al-17Si Alloy Powder Produced by Free Fall Atomizer
Abstract: In the present work the effect of process parameters on the characteristics of Al-17Si alloy powder produced by gas atomization using a free fall nozzle of different apex angles. The axial gas velocity away from the nozzle exit is measured for different operating pressures. The alloy was melted to a superheat temperature of 100, 150 and 200Ā°C and atomized by varying the gas flow rate and melt flow rate. The powder produced during gas atomization process generally exhibits a wide size distribution. ASTM standard sieve with vibratory shaker is used for powder analysis. The characterization of powder particles was accomplished by the parameters such as mass median, average size of powder particles; standard deviation and morphology of powder were studied by scanning electron microscopy. It is observed that decrease of apex angle results in axial velocity decreases in entire applied gas pressures range. Increase in apex angle results in decrease of gas jet length to metal stream collision, the median particle diameter of the powder increases resulting in decrease in particle irregularity. The median particle diameter of the powder has been shown to decrease almost linearly with increase in gas to melt flow (G/M) ratio. The sauter mean diameter variation, however, decreases slowly with increase in G/M ratio. Median particle diameter is significantly reduced with increase in the melt superheat
Microstructures and Mechanical properties of Spray deposited and Heat-treated Al-25Mg2 Si-2Cu alloy
The microstructural characteristics and Ā mechanical properties of Alā25Mg2Si-2Cu alloy were investigated. The alloy produced by spray atomization and deposition techniques followed by hot compression(HC) and age hardening(AGH) at 180ĀŗC for 2h and 2hĀ intervals after the solution heat treatment. The microstructure features of as cast, spray deposited (SD),hot compressed and heat-treated alloys were studied. the results show the microstructure of spray-deposited alloy mainly comprised of a uniform distribution ofĀ Ā intermettalicsĀ Ā ?-Mg2Si phase, ?- Al2Cu and Q phase in Al-matrix. Eliminating the porosity of deposit and fragmentation of the ? And Q phases is the main features during hot compression. After solution treating and age hardening, the microstructure found to be comprised of mainly Mg2Si phase in a fine spherical form. Large quantity of ?- Al2Cu phase and Q Phase less than 50 nm in size uniformly distributed in the Al- matrix during aging. These fine ? particles combined with the ? can significantly increase the tensile strength and hardness of the alloy. In the peak-aged condition is because of high concentration of Mg2Si and Al2Cu metastable phases. The microstructural features of alloys been investigated through Optical (OM) and Scanning electron microscopy (SEM) and analyses of phases were carried out using Energy dispersive X-ray( EDS).The improvement in the tensile and hardness properties of studied alloys was investigated by tensile test andĀ micro- hardness.Keywords: Al-Mg2Si alloy, Spray deposition, Age hardening, Microstructure, Mechanical properties,Ā Micro hardness
Wear behavior of secondary processed spray formed Al-28Si-5Cu-4Mg alloy
In the present study Al-28Si-5Cu-4Mg alloy has been spray formed and hot pressed
for densification. Hot pressing refined the microstructure and reduced the porosity in the
spray formed alloy from 10 to 1%. The microstructure of spray formed and hot pressed alloy
exhibited equiaxed grain morphology with fine and uniform distribution of both primary and
eutectic Si with fine needles of Q-Al 12 Si 7 Mg 4 Fe intermetallics and Chinese script like Īø-
Al 2 Cu precipitates in Ī±-Al matrix. The size of Si particles ranged from 3ā10 Āµm. In contrast
the microstructure of as-cast alloy consisted of coarse primary and eutectic Si, long needles
of Q-Al-Si-Mg-Cu-Fe phase and bright grey Īø-Al 2 Cu phase in the Ī±-Al matrix. The size of
primary Si varied from 30ā250 Āµm. The spray formed and hot pressed alloy exhibited a
higher hardness compared to the as-cast alloy. The wear behavior of both the alloys, under
dry sliding conditions, showed an increase in the wear rate with an increase in the load.
However, the spray formed and hot pressed alloy exhibited maximum wear resistance and
minimum coefficient of friction, while as-cast alloy exhibited minimum wear resistance and
maximum coefficient of friction over the entire range of applied load. The high wear
resistance and high hardness of spray formed and hot pressed alloy are explained in the light
of its microstructural modifications induced during spray forming and subsequent hot
pressing and also the topographical features of worn surfaces and morphology of debris
particles
Microstructural and Hardness of Spray Deposited Al-30Mg 2 Si-2Cu Alloy in Solutionized and Aged Conditions
An Alā30Mg 2 Si- 2Cu alloy was produced by spray
casting and the secondary processing such as hot compression and heat treatment were carried out. The coarsening behavior, distribution and size of the Mg 2 Si precipitates, the influence of
subsequent heat treatment on the microstructure were investigated Uniform distribution of Mg 2 Si was achieved by spray casting. The hardness tests were conducted on spray deposited, secondary processed and heat treated alloys. The results indicate that spray casting has strong influence on microstructure and hardness of the
material. The microstructural refinement of the alloy was enhanced during hot compression. The alloying with copper lead to further increase in strength by age hardening due to precipitation Al 2 Cu phase. A significant improvement in hardness was observed after hot compression and heat treatment
Tribological Analysis of Copper-Coated Graphite Particle-Reinforced A359 Al/5 wt.% SiC Composites
[[abstract]]Copper-coated graphite particles can be mass-produced by the cementation process using simple equipment.
Graphite particulates that were coated with electroless copper and 5 wt.% SiC particulates were
introduced into an aluminum alloy by compocasting to make A359 Al/5 wt.% SiC(p) composite that
contained 2, 4, 6, and 8 wt.% graphite particulate composite. The effects of SiC particles, quantity of
graphite particles, normal loading, sliding speed and wear debris on the coefficient of friction, and the wear
rate were investigated. The results thus obtained indicate that the wear properties were improved by adding
small amounts of SiC and graphite particles into the A359 Al alloy. The coefficient of friction of the A359
Al/5 wt.% SiC(p) composite that contained 6.0 wt.% graphite particulates was reduced to 0.246 and the
amount of graphite film that was released on the worn surface increased with the graphite particulate
content. The coefficient of friction and the wear rate were insensitive to the variation in the sliding speed
and normal loading.[[notice]]č£ę£å®ē¢[[incitationindex]]SCI[[booktype]]ē“ę¬[[booktype]]é»å
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