There may be classified not only for the size differences but also the way they are formed during the manufacturing. Pores are those regions which are trapped gaseous during the formations. They may be connected or not depending on the dispersed second phase particles, which may act as a nucleation sites because of the wetting potential difference.

Voids are formed by the accumulation of vacancies through the bulk diffusion, which may be driven by residual stress gradients if any or simply to reduce the surface free energy while keeping the total volume of the substance invariant.

There may be classified not only for the size differences but also the way they are formed during the manufacturing. Pores are those regions which are trapped gaseous during the formations. They may be connected or not depending on the dispersed second phase particles, which may act as a nucleation sites because of the wetting potential difference.

Voids are formed by the accumulation of vacancies through the bulk diffusion, which may be driven by residual stress gradients if any or simply to reduce the surface free energy while keeping the total volume of the substance invariant.

the voir and pore are similiar in the steelmaking

My guess is that a pore is open to the surface and is filled with air, whereas a void is internal and may contain air or other gasses, or none at all.

I think that such metal defects produced during casting should be called "porositiy". They usually contain any kind of gaseous remains and initiate failure.

In contrast to this "voids" are formed in intact material due to mechanical loading. This may be an accumulation of diffusing vacancies or damaged internal interfaces such as grain or phase boundaries e.g. due to creep crack growth.

Dear Sir,

Pores and voids are the defects in metal casting during solidification process. Both the defect is same, but the difference is size of the defects. if the defect size is smaller is called pores (Micro level), voids means, the defect size is bigger (Macro level).

Best of luck

Colleagues, I am sorry indeed. Void means empty. Could emptiness exist in the material world? It means that the void is a wrong term. Only pore may be used. Any other terms are emotions only.

Voids and pores geometrically often appear similar but not always, for example shrinkage pores. Scientifically the mechanisms of their formation is very much different. Here lies the engineering of their control. In short they are realised from the basic understanding of solubility of gas and the presence of gas in excess with supersaturation. Presence of gas too much in excess of supersaturation creates bouble in liquid metal and gives rise an ideal situation of void formation. Whereas pores basically form during solidification through release of gas by the primary solids. This mechanism gives various types of porosity with different size, shape, amount and distribution.

Thanks to all my respected seniors and colleagues for your time and expert opinion.

Porosity defects may be divided in

- gas porosity and

- shrinkage porosity.

Gas porosity in metal is related to the fact that solubility of gas is much higher in liquid than in solid state. Because of that during solidification gas has tendency to stay in liquid metal. It means that concetration of gas in remaining liquide part of metal will increase to the end of solidification process. Because of that after solidification on the place of gas concentration the gasseous pore will appear.

Shrinkage porosity is related to difficulties in feeding with liquid metal of certain areas in the casting during solidification. They can be divided into macro and micro pores. Macro pores are much larger than micro pores and they are more localized.

Micro pores mostly contain interconnected voids. These micro pores occur as a result of problems in feeding with liquid metal of interdendritic areas during solidification process due to the presence of dendritic arms.

Dear Musharaf

The difference between pores and voids is not only in the size scale, but also in the ways they form. The pores can be in a size scale ranging from nanometer to micrometer to meso-meter. In contrast, voids can be in a size scale ranging from meso-meter to millimeter.

In addition, on one hand, pores normally form during solidification of metals due to an evolution of gases to the surface of the solidifying metals. This manifestation of the evolution of gases usually occurs because the vapor pressure of the molten metals during solidification is higher than the atmospheric vapor pressure. On the other hand, voids normally develop as a consequence of a mechanical deformation, i.e., static or dynamic motion, of metals at high temperature, i.e., 0.45 Tm, where Tm is the melting temperature of the metals, as in the creep phenomenon of metals. At such situation, dislocations in the bulk of the metals normally either glide or clime up to grain boundary intersections, i.e., a triple point intersection or a second phase particle, and so on to pile up and form voids.

My dear,

Void is a generic term used to describe an empty pocket which happens

during solidification o a liquid metal. The void can be a porosity/ blow hole/

shrinkage. How ever the delineating factor is the size and shape of the defect. Porosity is mostly due to the evolution of Hydrogen during solidification which gets entrapped if sufficient time is not allowed for it to escape. The size will be that of a pinhead diameter or less and the inside surface smooth. Defect is intrinsic. Blow hole is due to multiple o gas evolution either from mold/core materials, air aspiration during pouring or due to turbulent flow of metal in the system. Shrinkage is due to the shrinking nature of the metal during solidification characterized by its very

rough surface and the size can be any thing. Shrinkage is divided into (1) Gross shrinkage and (2) Micro shrinkage which will resemble porosity but the inner surface will be rough. Only an experienced eye can diferentiate this. Hope this meets your requirements

A.V.Sethuraman

I am also interested in this question. Even after reading the answers kindly provided here, this question remains open for me. Best of all, I agree with Prof. Oğurtanı.

It would be great if one of you, fellow colleagues, could provide some references we could address to.

The difference between pores formation versus the voids formation in solid metals/alloys are the followings:

-Pores are formed in solid metals/alloys as a results of gases evolution during manufacturing and materials process, refer to the link:

1-Pore Formation in Solid during Manufacturing and Materials Processing.

http://www.tms.org/Communities/FTAttachments/Wei%20Pore%20Formation.pdf

-In contrast, voids are formed in solid metals/alloys as a result of diverse motions of dislocations during static & dynamic deformation of the metals/alloys, refer to the link;

2-Fracture characteristics of three metals subjected to various strains, strain rates, temperatures and pressures

file:///C:/Users/Habib/AppData/Local/Packages/Microsoft.MicrosoftEdge_8wekyb3d8bbwe/TempState/

Downloads/Fracturecharacteristicsofthreemetalssubjectedtovariousstrainsstrainratestemperaturesandpressures.pdf

Colleagues!

There is general influence, and there is particular one...

It is necessary to distinguish their influence, e.g., like it was done as in the attached, in - Vasylyev O.D., Firstov S.A. Toughening by pores. In: Advanced Multilayered and Fibre-Reinforced Composites. Ed. Y.M. Haddad, Dodrecht/Boston/ London, Kluwer Academic Publ, 1998. NATO ASI Series. 3. High Technology. vol.43, P.371-384.

Sorry for the non-convinient copy.

Cordially

O. Vasylyev

Dear all,

the correct English etymology of the word can be always found in the dictionary. Definition for the pore is an opening in the surface. Whereas void gives us an understanding of something "completely" empty like a piece of vacuum. So in my personal opinion you can call the opening near the surface - a pore. But if it is inside of the material and has no connection to surface it can be a void. There was no words about a size of a defect. The thing is the void can become a pore if we remove some surface (during polishing for example). When we talk about liquids it should be not the pores or voids, but gaseous bubbles. By the way in our native languages we can give the word pore our own meaning and it can vary from the English meaning, but if we want to speak high class English please refer to the oxford dictionary as a standard or ask a native speaker friend. I am also not an Englishman and can make mistakes.

Good luck,

Anton

in ferrous castings the porosity occurs due to lack of liquid metal available during end stage of solidification and also the evolving of gases during solidification.this can be differentiated from the size and location of pores. voids are due to liquid contraction which is not compensated with expansion

I can recommend Anton Pshenichnikov answer.

Voids are those created by evolving gasses that are traapped during solidification. Pores are those dissolved gasses like hydrogen, Nitrogen getting trapped during solidification. The mechnisms of formation of both are different