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| Experimental Study of Instability Mechanism on 1 200 MPa AdvancedHigh Strength Steel Sheets in the Process of Stamping |
| HE Chang-Wei, GUO Bi-Meng, WANG Wu-Rong, WEI Xi-Cheng |
| （School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China）
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Abstract The limit drawing formability of two advanced high strength steel sheets (AHSS) of tensile strength 1 200 MPa with the cup drawing test was studied. Their instability and failure mechanisms were also discussed from the standpoint of the microstructure. The results show that the limiting drawing ratio (LDR) of the DP1200 and the M1200 are 2.03 and 1.99, respectively. Their uniaxial tensile properties are difficult to accurately reflect the forming performance of material under the complex stress state. A large number of dimples on the fracture surfaces can be seen, which testifies the ductile fracture mode, but the crack propagation mechanism is not the same. For DP1200 steel, the failure mode is the crack propagation along the ferrite/martensite interfaces as well as through the martensitic grains. In M1200 steel, the crack propagates along the martensite interfaces.
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Received: 12 December 2011
Published: 28 September 2012
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