I am working on the Aluminium based metal matrix composites. For mechanical characterization need to know possible effect of porosity on the properties like Ultimate tensile strength, % elongation, microhardness, impact strength etc.
Dear Dr. Pardeep Saini ,
generally, increasing content of porosity will decrease the mechanical properties of MMC such as tensile strength, Young's modulus, Poisson ratio, and damping capacity. The presence of porosity decreased the mechanical properties of cast MMC as the failure process is initiated from the voids formed. Porosity has detrimental effects on the mechanical properties of castings because it introduces defects into the material composition. These defects are created by either shrinkage or trapped gases which both cause air pockets within the final cooled metal.
For more details, please see the following sources:
-EFFECTS OF POROSITY ON MECHANICAL PROPERTIES OF METAL MATRIX COMPOSITE: AN OVERVIEW
S. N. AQIDA, M. I. GHAZALI & J. HASHIM
Jurnal Teknologi, 40(A), 17–32 (2004)
Available at: http://eprints.utm.my/id/eprint/1529/1/JTJUN40A02.pdf
-THE EFFECT OF POROSITY ON FATIGUE FOR CAST METAL MATRIX COMPOSITES
S.N. Aqida, M. I. Ghazali, J. Hashim
No journal info. (2015)
Available at: https://www.researchgate.net/publication/266054224_THE_EFFECT_OF_POROSITY_ON_FATIGUE_FOR_CAST_METAL_MATRIX_COMPOSITES
-Porosity in aluminium matrix composites: cause, effect and defence
Devinder Priyadarshi, Rajesh Kumar Sharma
MS AIJ,14(4) (2016)
Avaliable at: https://www.tsijournals.com/articles/porosity-in-aluminium-matrix-composites-cause-effect-and-defence.pdf
-A Review on Properties of Aluminium Based Metal Matrix Composites via Stir Casting
V. Rama koteswara Rao, J. Rangaraya Chowdary, A.Balaji, D.Sai Krishna, B.P.R.Bhavabhuthi, G.Sreevatsava, K.Abhiram
International Journal of Scientific & Engineering Research, Volume 7, Issue 2 (2016)
Available at: https://www.ijser.org/researchpaper/A-Review-on-Properties-of-Aluminium-Based-Metal-Matrix-Composites-via-Stir-Casting.pdf
Enjoy reading and my best regards. Pierluigi Traverso.
Dear Dr. Pardeep Saini
Porosity negatively influence all mechanical properties you mentioned, as well as the fatigue performance, fracture toughness, machinability, toughness, ductility, thermal and electrical conductivity.
Porosity in Aluminium matrix composites deteriorates the mechanical properties of the material. Porosity is observed when adding more weight percentage of reinforcement particles in the Alunimium matrix. This is due to the density difference between the matrix and reinforcement, agglomeration of secondary particles, air entrapped during stirring and poor selection of stirring parameters.
However, porous components are widely used for sound absorption, heat insulation, and electrical applications. Powder metallurgy process is intentionally used to develop porous parts such as self lubricating bearings, porous metals for filtering .
(1) Reduces the cross sectional area to support the tensile load and causes premature failure.
(2) Acts as a stress raiser to accelerate failure.
(3) If pores are located at the particle matrix interface, load transfer to the reinforcement particle will not occur.
(4) Diminishes plastic deformation during tensile loading which limits ductility.
(5) Usually random size and randomly distributed pores occur in the fabrication of aluminum matrix composites. The composite would further lose the ability to absorb energy and impact strength would go down.
(6) Sometimes, the tensile specimen may fail outside gauge length portion because of porosity concentration.
porosity is the defect reduces the strength of the material, wettability is the main reason for occurring porosity.
Porosity is a casting defect. These defects are created by either shrinkage or trapped gases which both cause air pockets within the metal. Which is responsible for reducing the mechanical properties of Al based metal matrix composite like tensile strength, young's modulus, fatigue and percentage elongation. Because porosity acts as a nucleation site for crack initiation and crack propagate in the specimen, ultimately failure of material takes place.
For more details, please see:
https://www.sciencedirect.com/science/article/pii/S0921509320308649
1. One can see pore as a new free surface wherein required cohesive forces that exist between the atoms (bonds) are missing.
2. Magnitude of modulus of elasticity E decreases with volume fraction porosity.
3. Pores act as stress raisers - have ability to amplify an applied stress in their locale.
4. Act as nucleation for crack extension (can try to correlate with Griffith Theory)
5. Affects fracture toughness adversely
Porosity in ALMMC deteriorates the mechanical properties of the material.
The surface, sub-surface, and internal porosity have a significant impact on the strength and stiffness properties of the parts produced by the processes of PBF. The surface porosity can be reduced in these parts by using finer powder particles, which leads to higher ratios of material transportation. https://iopscience.iop.org/article/10.1088/2053-1591/abcc5d
To reduce porosity in composites fabrication, proper casting process parameters selection is important.
Porosity in cast metal matrix composite (MMC) has been known as a defect affecting the enhancement of strength, particularly in particle-reinforced MMC. From previous reviews, among the causes of porosity formation are air bubbles entering the melt matrix material, water vapour on the particles surfaces, gas entrapment during mixing process, evolution of hydrogen, and shrinkage during solidification. Kindly find the information from this paper.
https://core.ac.uk/download/pdf/11778134.pdf
Porosity decreases the mechanical properties because they act as a starting point for failure in the material. Shrinkage porosities are more critical as it is usually longer with sharp edges as compared with gas porosities that are more rounded. stress builds up at these notches and causes early failure in the material.
- Badges
- Science topic