Table of Contents
Why is it that cross slip in bcc and FCC metals is easier than that in HCP metals How does this influence the ductility of BCC FCC and HCP metals?
How does this influence the ductility of BCC, FCC, and HCP metals? The cross slips in hexagonal close-packed (HCP) metals are not easy because the slip planes do not intersect. The cross slips in case of face-centered cubic (FCC) and body-centered cubic (BCC) metals are comparatively possible because they intersect.
Does FCC or BCC have more slip planes?
Although the number of possible slip systems is much higher in bcc crystals than fcc crystals, the ductility is not necessarily higher due to increased lattice friction stresses.
Why is FCC more malleable than BCC?
This is because their symmetry provides closely packed planes in several directions. A face-centered cubic crystal structure will exhibit more ductility (deform more readily under load before breaking) than a body-centered cubic structure. The bcc lattice, although cubic, is not closely packed and forms strong metals.
Why is BCC ductile to brittle transition?
The ductile/brittle transition effect occurs because the development of the plastic zone in some types of metals is a temperature-dependent process. At high temperatures, there is sufficient thermal energy in the crystal structure to aid the movement of dislocations under an externally applied stress.
Why are BCC metals stronger than FCC?
The BCC structure is slightly less closely packed than FCC or HCP and is often the high temperature form of metals that are close-packed at lower temperatures. When the metal is deformed, the planes of atoms must slip over each other, and this is more difficult in the BCC structure.
Why are FCC metals more ductile as compared to BCC metals?
This is because their symmetry provides closely packed planes in several directions. A face-centered cubic crystal structure will exhibit more ductility (deform more readily under load before breaking) than a body-centered cubic structure.
Is FCC more dense than BCC?
Because FCC atoms are arranged more closely together than BCC atoms, FCC metals will tend to be more dense and more stable. This is a very broad rule, however! Tungsten, one of the densest metals, is BCC. However, you can do one classic experiment to see the density change between BCC and FCC.
Are bcc metals brittle?
At high temperatures, FCC and BCC structured metals both have mobile dislocations, and thus they can sustain large plastic deformations without undergoing fracture. This lack of dislocation movement makes BCC brittle, while FCC stays ductile.
Why is FCC more ductile than bcc?
Yes, You are right that BCC has more no. of slip systems than FCC and still FCC is more ductile than BCC because slip planes in FCC are more closed packed than the slip planes in BCC. Ok so this is a very blunt statement and a good understanding of slip systems have to be developed to actually digest this simple fact.
What is the difference between FCC and BCC slip systems?
It doesn’t lattice to another. FCC has a higher packing efficiency around 74\% and the slip planes are more closely packed and slip systems around 12 lesser than BCC. Infact BCC has more slip systems around 48 more than FCC. But they are not as closely packed as FCC. For plastic deformation, we need at least 5 independent slip systems.
Why does BCC have 48 slip planes?
But you must understand that because there is no definite slip plane as there was in FCC so differnt planes of BCC having nearly equal atomic density are competing for slip to occur. That is the only significance of having 48 slip planes.
How many slip systems are there in bcc crystals?
However, the {100} system also has atoms packed close enough to be considered a valid slip system. There are 12 total slip systems, 5 independent. If there are at least 5 independent slip systems, the metal is ductile! BCC crystals have 48 slip systems but still only 5 are independent.