How many close-packed planes bcc?
BCC slip occurs on close-packed planes in close-packed directions. There are 4 close-packed directions: [111], ~ 11], (111], and [111] for the (11.0) plane. Close-packed planes in BCC are {lID}, {112}, and {123}.
What is the family of close-packed directions in bcc iron?
The equivalent family of directions in the FCC structure are the < 110 > directions. < 110 > represents the directions [110], [110], [101], [101], [011], [011 ] and their negative [ 1 10], etc. The close-packed directions in bcc are the directions < 111 > (body diagonal of the unit cell).
What is the coordination number of bcc?
8
Coordination number – the number of nearest neighbor atoms or ions surrounding an atom or ion. For FCC and HCP systems, the coordination number is 12. For BCC it’s 8.
Which plane is the most densely packed in bcc crystal structure?
| Structure | Close packed planes |
|---|---|
| Simple cubic (SC) | None |
| Body-centered cubic (BCC) | Six {110} |
| Face-centered cubic (FCC) | {111} |
| Hexagonal close-packed (HCP) | Basal planes: (0001), (0002); Prismatic planes: one of the three {10-10} planes; Pyramidal planes: one of the six {10-11} |
Is HCP stronger than BCC?
BCC metals are less ductile but stronger, eg iron, while HCP metals are usually brittle.
What is coordination NO in CCP and BCC?
-bcc stands for body centered cell and the coordination number is 8. -fcc stands for face centered cell and the coordination number is 12. -ccp stands for cubic close packed and the coordination number is 12.
Is hcp stronger than BCC?
Why is BCC more brittle than fcc?
Why are FCC metals ductile, HCP metals brittle and BCC metals tough? FCC has 12 slip planes with 4 closest packed planes {111} and 3 closest packed directions per plane <110>. HCP has only 3 slip systems. BCC does not have truly closest packed planes so slip must be thermally activated in BCC metals.
Is BCC more brittle than FCC?
How do you think the ductility of BCT (body centered tetragonal) crystals would compare with BCC and FCC crystals? We expect the BCT structure to have fewer active slip systems and lower ductility (higher brittleness) compared to BCC and FCC crystals.
How many closed packed directions are in a BCC cell?
There are 6 planes of this type, and each contains two close packed directions. Consideration of fig. 1b and 2b shows the closed packed direction joins diagonally opposite corners of the BCC unit cell. It is therefore a (111) direction. As there are two (111) for each {110} plane there is a total of 12 possible combinations of {110} and (111).
What are the stacking faults in HCP and BCC?
The FCC, HCP and BCC Crystal Structures 3. Stacking faults in Close-Packed Structures (a) An intrinsic stacking fault in FCC can be considered as a missing close-packed plane, and an extrinsic fault as an additional close-packed plane. Write down the stacking sequences for these two faults.
How are stacking faults considered in close packed structures?
Stacking faults in Close-Packed Structures (a) An intrinsic stacking fault in FCC can be considered as a missing close-packed plane, and an extrinsic fault as an additional close-packed plane. Write down the stacking sequences for these two faults. (b) How would one convert FCC to HCP by a Shockley partial dislocation mechanism?
What kind of stacking is hexagonal close packing?
The {ABAB… } type stacking of close packed layers is called Hexagonal Close Packing (hcp) because the smallest lattice repeat is a Primitive Hexagonal unit cell. In the primitive hexagonal cell we have 1 atom at each of the corners of the cell (each is “worth” 1/8) and 1 atom within the cell giving us 2 atoms/unit cell.
