ductility and fracture toughness

[hotfusion]

How can I quantify (in terms of %ductility) the fracture toughness of a (sintered) metal?

 

[metengr]

Without actual tensile and fracture toughness test data to compare and establish your own correlation for the sintered metal, you cannot quantify ductility in terms of fracture toughness for sintered metals. There are too many variables (binder used for sintering and porosity level) that will effect results.

Ductility is a measure of the ability of a material to deform plastically without fracturing, as measured by % elongation or % reduction of area. For wrought materials one could make the correlation that ductile material will exhibit increased fracture toughness, because fracture toughness is the ability of a material to resist crack propagation.

 

[hotfusion]

I have ductility data for two types of a sintered metal, they are rather different 5-10% in one case and over 15% in the other case. Also the price is very different. I need to justify the choice of one or the other, I thought ductility was a good parameter, as for us limited (ideally zero) crack growth is important.
How can I link (a bit better than qualitatively) ductility with reduced crack propagation?

 

[metengr]

Depending on your application you may need to factor the strength of the sintered product, as well. If strength is not important and all you are looking for is to have a ductile sintered product, go with the product that provides 15% ductility. Most likely, this would have greater resistance to crack initiation and propagation because of the metal powder and binder that was used. Intuitively, the sintered product with the higher strength would have reduced ductility and probably lower tolerance to crack initiation and propagation.

Other than this, there are no equations or formulas that will provide an answer. I would contact the manufacturers of the sintered products and ask them if they have any specific test data related to your application.

 

[meng10]

What are the expected values from charpy V notch testing of A36 steel at 0, -20, -40, -50 deg C? I do not have access to ASTM A673, so I cannot tell if this info is in that std.

 

[Carburize]

Meng10 - what thickness of material are you interested in?

 

[metengr]

ASTM A673 is a standard that describes the procedure for longitudinal Charpy V-notch impact testing of structural steel and testing frequency. There are no impact test requirements for A 36 in this specification.