Advanced Materials - 230509

Question 1

TRIP effect

Answer 1

• Transformation induced plasticity
• Lattice transformation during forming.
  Austenite –> Martensite + ferrite + some other kinds of grains (good strength behavior). (Phase transformation)
• Manganese.

Question 2

TWIP effect

Answer 2

• Twinning induced plasticity
• Deformation to the microstructure according to the twin planes.
• Increase of formability, additional forming mechanism.
• twin boundary: hindrance of dislocation movement.
• Manganese.

Question 3

Press hardening steel (PHS)

Answer 3

22MnB5 - 0.22 percent carbon steel is mostly used, 1.25 Manganese (there’s a factor of 4: 5/4 = 1.25%)

Regular steel - quenching - martensite

• Direct process: Austenite (furnace, 1000 C), forming tool with cooling pipes (hot forming and quenching) martensite, blanking, surface conditioning. UTS up to 1800 MPa
• Indirect: first blanking and cold forming, austenite, form hardening and surface treatment.
• ## Ductility and strength vary.
• growing trend

Question 4

Boron effect

Answer 4

Adding the B will move the ferrite and the perlite areas to the right (more time will be needed to get to this transformation phases).
The cooling can be slower and still we get some only martensite.

Question 5

Advantages

Answer 5

• High UTS
• weight reduction
• no springback
• press forces are reduced up to 1/3 or 1/4 compared to cold forming.

Question 6

Disadvantages

Answer 6

• Big furnace
• New process, not so much expertise.
• Trimming requires high forces and leads to wear. Laser can be used instead.

Question 7

Zinc coating

Answer 7

The zinc coating will transform to zinc iron.
Aluminum coating is also possible.

Question 8

Partial press hardening

Answer 8

B Pillar:
* lower area: high energy absorption capacity (ferrite + cementite)
* upper area: very strong material (martensite)
* Furnace: one area is heated, the other is not, both are quenched.
* Tailored tempering: controlled cooling.

Answer 9

kaltumgeformt
warmumgeformt