let’s think that there are two fcc metals.
Both metals are deformed by only dislocation slip, but strength/hardness is different each other such as Al or Cu.
Is there common parameter explanining a reason?
I firstly think Shear modulus, because theoretical strength is expressed with it.
But I’ve found that the modulus doesn’t show any relation with strength in many metals.
Is this only nature of metal?
dear Seok Su Sohn,
I have the Impression that their is a Kind of mixup of technical Terms and theoretical considerations. Fact is, that the tensile as well as shear strength of e.g. Al and Cu is different as well as the Youngs moduli and the shear moduli are different. So what are you exactly looking for at which conditions (any sketch)?
Best regards, R.R.
There is some relation between shear modulus and strength because the shear modulus enters in the strength contribution of dislocation obstacles like the Orowan mechanism.
But of course the strength is influenced by a lot of other things as well:
purity, initial dislocation density, precipitations, grain size etc.
Dear Seok Su Sohn,
Metal properties can be divided into extrinsic and intrinsic properties. Strength is an extrinsic property, depending on composition, deformation applied, grain size, etc as is noted above. Intrinsic properties depend on the behaviour of atoms and electrons. The thermal expansion coefficient and the elastic constants depending on the binding forces within metals are intrinsic properties. This means that the elastic constants differ from metal to metal, but are surprisingly independent on the alloy composition. Alloying often aims at the improvement of strength. Intrinsic properties are interrelated via the Grüneisen constant. An introduction to this approach valid for isotropic metals is given in Section 2.2.4 of the Reference.
Reference
Materials Science in Design and Engineering, Delft NL, 2012.
http://www.delftacademicpress.nl/m017.php
You need to specify the process parameters used during the manufacturing or production of the part under study. You can design you experiment in order to investigate the effect of these process parameters on the metal strength. This is the scientific approach to answer your question. Good Luck
Al & Cu both may be FCC but their number of active slip planes which causes deformation at a particular temperature varies. The critical resolved shear stress also may vary because of the different densities of planes. Both of them are important parameters when it comes to the strength of a metal.
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