A novel 22MnMoB hot stamping steel was designed. The continuous cooling transformation （CCT） measurement of the 22MnMoB steel showed that the ferrite-bainite microstructure could be obtained at cooling rates lower t...A novel 22MnMoB hot stamping steel was designed. The continuous cooling transformation （CCT） measurement of the 22MnMoB steel showed that the ferrite-bainite microstructure could be obtained at cooling rates lower than 25 ℃/s, and the complete martensite structure required the cooling rate higher than 30 ℃/s. The experiments with non-uniform die temperatures were carried out to obtain tailored properties. The results showed that strength of 1 411 MPa and elon- gation of 6% could be obtained in the hard zone, and strength of 916 MPa and elongation of 9% could be obtained in the soft zone, which can be realized by controlling the die temperature at 400 ℃. The transition zone was found smooth and could be beneficial to reduce the stress concen tration and therefore improve the performance of components.展开更多
Phase stability,elastic properties,thermo-physical properties,as well as electronic properties of hexa-（Mo,Cr,W）2C carbides were investigated by first-principles calculations.The results indicated that the Mo8C4,Mo7...Phase stability,elastic properties,thermo-physical properties,as well as electronic properties of hexa-（Mo,Cr,W）2C carbides were investigated by first-principles calculations.The results indicated that the Mo8C4,Mo7Cr1C4,Mo7W1C4,Mo6W2C4,and Mo6W1Cr1C4 are stable and the stability follows the sequence：Mo6W1Cr1C4〉Mo7W1C4〉Mo7Cr1C4〉 Mo6W2C4〉 Mo8C4.Mo6W1Cr1C4 shows the highest stability,deformation resistance and hardness.G/B（shear modulus/bulk modulus）and Poisson′s ratio of the stable hexa-（Mo,Cr,W）2C are all larger than 1.75 and 0.26,respectively,which indicates that they are all brittle.The anisotropies are mainly due to the different Vogit shear modulus/Reuss shear modulus;the mechanical anisotropy of Mo7Cr1C4 is the largest,and that of Mo8C4 is the smallest.Moreover,the obtained Debye temperatureΘDand heat capacity Cpindicate that Mo6W2C4 possesses the best thermal conductivity（ΘD=497.72K）,while Mo7Cr1C4 and Mo6W2C4possess the largest heat capacity when the temperature is in the range of 0-10 Kand larger than 10 K,respectively.From the electronic property analysis,the doped Cr and W atoms can not only participate in orbitals hybridization themselves but also enhance the orbitals hybridization between Mo and C atoms,which can reinforce the interatomic interactions.展开更多
基金financially supported by National Natural Science Foundation of China(Grant No.U1560204)Fundamental Research Funds for the Central Universities(Grant No.N150705001)National Key Research and Development Program of China(Grant No.2016YFB0101605)
文摘A novel 22MnMoB hot stamping steel was designed. The continuous cooling transformation （CCT） measurement of the 22MnMoB steel showed that the ferrite-bainite microstructure could be obtained at cooling rates lower than 25 ℃/s, and the complete martensite structure required the cooling rate higher than 30 ℃/s. The experiments with non-uniform die temperatures were carried out to obtain tailored properties. The results showed that strength of 1 411 MPa and elon- gation of 6% could be obtained in the hard zone, and strength of 916 MPa and elongation of 9% could be obtained in the soft zone, which can be realized by controlling the die temperature at 400 ℃. The transition zone was found smooth and could be beneficial to reduce the stress concen tration and therefore improve the performance of components.
文摘Phase stability,elastic properties,thermo-physical properties,as well as electronic properties of hexa-（Mo,Cr,W）2C carbides were investigated by first-principles calculations.The results indicated that the Mo8C4,Mo7Cr1C4,Mo7W1C4,Mo6W2C4,and Mo6W1Cr1C4 are stable and the stability follows the sequence：Mo6W1Cr1C4〉Mo7W1C4〉Mo7Cr1C4〉 Mo6W2C4〉 Mo8C4.Mo6W1Cr1C4 shows the highest stability,deformation resistance and hardness.G/B（shear modulus/bulk modulus）and Poisson′s ratio of the stable hexa-（Mo,Cr,W）2C are all larger than 1.75 and 0.26,respectively,which indicates that they are all brittle.The anisotropies are mainly due to the different Vogit shear modulus/Reuss shear modulus;the mechanical anisotropy of Mo7Cr1C4 is the largest,and that of Mo8C4 is the smallest.Moreover,the obtained Debye temperatureΘDand heat capacity Cpindicate that Mo6W2C4 possesses the best thermal conductivity（ΘD=497.72K）,while Mo7Cr1C4 and Mo6W2C4possess the largest heat capacity when the temperature is in the range of 0-10 Kand larger than 10 K,respectively.From the electronic property analysis,the doped Cr and W atoms can not only participate in orbitals hybridization themselves but also enhance the orbitals hybridization between Mo and C atoms,which can reinforce the interatomic interactions.
