Q2. What have the authors contributed in "Stir casting process for manufacture of al–sic composites" ?
In this study, micron-sized SiC particles were used as reinforcement to fabricate Al-3 wt % SiC composites at two casting temperatures ( 680 and 850 C ) and stirring periods ( 2 and 6 min ). Factors of reaction at matrix/ceramic interface, porosity, ceramic incorporation, and agglomeration of the particles were evaluated by scanning electron microscope ( SEM ) and high-resolution transition electron microscope ( HRTEM ) studies.
Q3. What was the origin of the porosity in cast MMCs?
It was reported that the porosity in cast MMCs was originated from gas entrapment during stirring, water vapor (H2O) on the surface of ceramic particles, hydrogen evolution, air bubbles entering the slurry as an air envelope to the reinforcement particles, and shrinkage during solidification process [9].
Q4. What was used to study the reaction at the interface of the aluminum matrix and SiC particles?
A high-resolution transmission electron microscope (HRTEM, Philips CM200) at an accelerating voltage of 200 kV was also used to study the reaction at the interface of the aluminum matrix and SiC particles.
Q5. What was the effect of the stirring time on the ceramic particles?
Gas pores, solidification shrinkage, and air gap between the agglomerated ceramic particles were observed in the samples after stir casting, while by changing the stirring time and temperature, the type and the amount of porosities could be altered.
Q6. What is the main aim of this study?
The main aim of this study is to lessen the number of defect locations within AMMCs produced from the stir casting method and hence to improve the quality of the fabricated composites.
Q7. What are the main considerations for achieving AMMC via stir casting?
the following considerations for achieving AMMC via stir casting must be considered: no adverse chemical reaction between the reinforcement material and matrix alloy, no or very low porosity content in the cast AMMCs, wettability between the two main phases, and a uniform distribution of the reinforcement material.
Q8. What was used to evaluate the characterization of a ceramic particle in Sample 3?
Line energy dispersive X-ray spectroscopy (EDX) microanalysis (Fig. 6) was used to evaluate thechemical characterization around a ceramic particle in Sample 3.
Q9. What is the characterization of the Al4C3 phase?
After characterization, needlelike Al4C3 phase is detected with a different orientation growth from the crystalline plane orientations of silicon carbide.
Q10. What is the effect of a higher stirring temperature on the ceramic particles?
A higher stirring temperature would lead to a further incorporation of ceramic particles into the molten pure aluminum with an improved distribution.
Q11. What is the occurrence of the on-set of aluminum melting?
As can be seen, the on-set of aluminum melting is evident from about 650 C (endothermic peak) and just after this, an exothermic trend could be observed, which corresponds to the occurrence of a reaction between Al and SiC, leading to a large release of heat.
Q12. How long is the stirring time required for the ceramic particles to be in contact with the melt?
No suitable bonding was obtained at the metal/ceramic interface for the stirring time of 2 min, indicating that a minimum stirring time is necessary for ceramic particles to be in contact with the melt to form a strong bond with the matrix.
Q13. What is the effect of shrinkage porosity on the composite?
The considerable formation of shrinkage porosity at the interface significantly reduces the strength of the composite, even though it has a larger amount of ceramic particle incorporations.
Q14. How long does it take to form a bond between Al and SiC?
Stirring for 2 min at 680 C is not along-enough period or high-enough temperature combination process for the migration of carbon atoms and the formation of suitable bond between Al and SiC particles.
Q15. How many ceramic particles were incorporated into the molten aluminum?
The amount of ceramic particles incorporated into the molten aluminum was determined by leaching the composite using 2 mol L -1 hydrochloric acid, resulting in the removal of aluminum phase.
Q16. What are the important factors in determining the AMMC ductility?
it could be concluded that the presence of ceramic particles and the formation of shrinkage porosities around the particles are the two most important factors in determining the AMMC ductility as well as the mechanical properties in general.
Q17. What is the effect of the stirring time on the ceramic particles?
Agglomeration of the micron-sized SiC particles could be observed in all the samples, indicating that the stirring time, temperature, and viscosity of the melt could not affect this phenomenon.
Q18. What was the onset reaction temperature between pure aluminum and SiC powders?
In order to determine the onset reaction temperature between pure aluminum and SiC powders, differential scanning calorimetry (DSC, Netzsch STA 409, Germany) was performed.