1. It is found that the fracture of TWIP steel is typical ductile fracture pattern and its deformation and fracture mechanisms are the formation, growth and coalescence of micro-voids.

2. The microstructure of different annealing treatment for TWIP steel before and after tensile deformation was investigated by static and TEM.

3. It was found that the fracture of TWIP steel was typical ductile fracture pattern and its deformation and fracture processes were the formation, growth and coalescence of microvoids.

4. The microstructure of Twinning Induced Plasticity (TWIP) steel during tensile deformation was investigated with SEM and TEM.

5. The results show that there are 60% annealing twins in TWIP steel before deformation and 32% deformed twins after deformation.

6. A large amount of strain marks were observed in the tension specimens of the TWIP steel. The strain marks consist of slip lines and small mechanical twins.

7. On the deformation process the annealing twins transform into deformation twins , which is TWIP effect,[sentencedict .com] and so th.

8. Mechanism of the twinning induced transformation, impact of stacking fault energy on TWIP effect and impact of microstructure on mechanical properties of the steel were introduced.

9. The mechanism of twinning induced plasticity, the impact of stacking fault energy on TWIP effect and the excellent mechanical properties of TWIP steel are emphatically introduced.

10. In order to meet the needs for new generation automobile industry in the future, a lot of new steel are developing in the word, they are AHSS, HSS, DP steel, TRIP steel, TWIP steel etc.