For AMMCs the relative density increases or decreases...if it is decreasing then it is possible or not.
Dear Vikas,
As a thumb rule, sintering is a process used for densification of a structure from it's (green) form. Hence, the relative density is bound to increase provided no chemical reaction is encountered during the process.
I hope it helps.
Attached is a paper that addresses porosity development during sintering of CMMC but the principle should be applicable to AMMC as well. Direct contact amongst filler particles seems to give rise to higher porosity as compared to the case where the fillers are coated to prevent direct contact. My interpretation is that the type of filler material plays a major role in determining whether the porosity will increase or decrease after sintering. AMMC's have different kinds of filler materials and if the filler-filler diffusion bonding is not good compared to filler-coating-filler diffusion bonding, porosity in the former may reduce the density after sintering whereas in the coated filler MMC the logical trend (density increasing after sintering) may be observed of reduced porosity as explained in the attached paper.
Hi Vikas....
Sintering is a process done to increase the density of green body, but it's not the thumb rule that it will always increase with sintering. It depends on the temperature conditions you are providing to the sample. Sometimes the temperature you are providing for sintering is low, the density will not improve but in case you provide appropriate temperature and you are able to improve the density of green body then repeating the same step to make it more dense at same temperature or little bit increased temperature may decrease or increase the density of the green body, both the cases are possible.
Dear Vikas,
Have a look to the following articles:
Siddhartha Tiwari, Priyanka Rajput, and Sanjay Srivastava
Densification Behaviour in the Fabrication of Al-Fe Metal Matrix Composite Using Powder Metallurgy Route
http://www.hindawi.com/journals/isrn/2012/195654/
C. Padmavathi, Anish Upadhyaya
Densification, Microstructure and Properties of Supersolidus
Liquid Phase Sintered 6711Al-SiC Metal Matrix Composites
http://www.iiss.sanu.ac.rs/download/vol42_3/vol42_3_11.pdf
If there is a blowing component in the green body, most probably density will decrease at high temperature applications.
Dear Vikas Shrivastava
1-The relative density of the Aluminum metal matrix composites increased with increasing Al2O3 particle size in (pure aluminum matrix of composite) up to 12 µm.
2- The raising the particle size of Al2O3 to 48 µm led to abrupt reduction in relative density. The relativedensity of unreinforced Al was higher than that of the Al–Al2O3 composite.
Please you can be seen that above conclusions in these attaches below.
Best regards
przyrbwn.icm.edu.pl/APP/PDF/121/a121z1p32.pdf
During sintering you can have either swelling or shrinkage. What type of behaviour you find depends on various factors and important empirical observations can be interpreted in terms of the phase diagram as shown by German in his books on sintering. Eg Cu gives swelling and C shrinkage when sintering iron powder.
when sintering the titanium grade 5 alloy with different composition of other material, the density is decreasing with increasing the percentage of other material. May i know the reason?
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