The specimens of 1Cr-0.5Mo low alloy steel, undoped, Sn-doped and Ce＋Sn-doped, were austenitized at 1300 oC and then cooled down to different temperatures in the range of 700–1050 oC, followed by tensile tests with ...The specimens of 1Cr-0.5Mo low alloy steel, undoped, Sn-doped and Ce＋Sn-doped, were austenitized at 1300 oC and then cooled down to different temperatures in the range of 700–1050 oC, followed by tensile tests with the aid of a Gleeble machine. The reduction of area（RA） obtained from the test was employed to evaluate the hot ductility of the steel. The tested specimens were characterized using different techniques. Minor Sn could considerably reduce the RA values of the steel in the whole temperature range, and the hot ductility curve could be widened and deepened. Nevertheless, minor Ce could improve the hot ductility of the Ce＋Sn-doped steel by fully suppressing the Sn-induced hot ductility deterioration. FEGSTEM microanalysis showed that the Sn or Ce and Sn atoms segregated to austenite grain boundaries in the Sn-doped or Ce＋Sn doped specimens. The detrimental effect of Sn on the hot ductility could be attributed mainly to the segregation of Sn as it could decrease the grain boundary cohesion and in turn enhanced the grain boundary sliding and cracking. However, this detrimental effect of Sn could be counteracted by the segregation of Ce which could increase the grain boundary cohesion and in turn restrained the grain boundary sliding and cracking. Accordingly, a minor addition of rare earth Ce could be an effective method of suppressing the detrimental effect of impurity elements on the hot ductility of a Cr-Mo low alloy steel.展开更多
The effect of rare earth（RE） on creep rupture of economical 21Cr-11Ni-N heat-resistant austenitic steel was investigated at 650 °C under different stress levels. It was found that RE could increase the time to ...The effect of rare earth（RE） on creep rupture of economical 21Cr-11Ni-N heat-resistant austenitic steel was investigated at 650 °C under different stress levels. It was found that RE could increase the time to creep rupture, especially at long-term creep duration. The logarithm of the time to creep rupture（lgtr） was a linear function of the applied stress（σ）. RE addition was favorable to generating a high fraction of low-coincidence site lattice（CSL） boundaries which was a possible cause for improving the creep rupture resistance. The fracture surface of RE-added steel exhibited less intergranular cracks suggesting the alteration on the nature of grain boundaries due to the presence of RE. RE addition changed the morphology of the intergranular chromium carbides from continuous network shape to fragmentary distribution which was another cause for longer creep duration. These results strongly suggested that the effect of RE alloying played a crucial role in improving the creep rupture resistance.展开更多
基金Project supported by the National Natural Science Foundation of China(51071060)
文摘The specimens of 1Cr-0.5Mo low alloy steel, undoped, Sn-doped and Ce＋Sn-doped, were austenitized at 1300 oC and then cooled down to different temperatures in the range of 700–1050 oC, followed by tensile tests with the aid of a Gleeble machine. The reduction of area（RA） obtained from the test was employed to evaluate the hot ductility of the steel. The tested specimens were characterized using different techniques. Minor Sn could considerably reduce the RA values of the steel in the whole temperature range, and the hot ductility curve could be widened and deepened. Nevertheless, minor Ce could improve the hot ductility of the Ce＋Sn-doped steel by fully suppressing the Sn-induced hot ductility deterioration. FEGSTEM microanalysis showed that the Sn or Ce and Sn atoms segregated to austenite grain boundaries in the Sn-doped or Ce＋Sn doped specimens. The detrimental effect of Sn on the hot ductility could be attributed mainly to the segregation of Sn as it could decrease the grain boundary cohesion and in turn enhanced the grain boundary sliding and cracking. However, this detrimental effect of Sn could be counteracted by the segregation of Ce which could increase the grain boundary cohesion and in turn restrained the grain boundary sliding and cracking. Accordingly, a minor addition of rare earth Ce could be an effective method of suppressing the detrimental effect of impurity elements on the hot ductility of a Cr-Mo low alloy steel.
基金Project supported by the National Natural Science Foundation of China(51101136)Natural Science Foundation of Hebei Province(E2012203013)+1 种基金College Science and Technology Research Project of Hebei Province,China(QN2014107)College Innovation Team Leader Training Program of Hebei Province,China(LJRC012)
文摘The effect of rare earth（RE） on creep rupture of economical 21Cr-11Ni-N heat-resistant austenitic steel was investigated at 650 °C under different stress levels. It was found that RE could increase the time to creep rupture, especially at long-term creep duration. The logarithm of the time to creep rupture（lgtr） was a linear function of the applied stress（σ）. RE addition was favorable to generating a high fraction of low-coincidence site lattice（CSL） boundaries which was a possible cause for improving the creep rupture resistance. The fracture surface of RE-added steel exhibited less intergranular cracks suggesting the alteration on the nature of grain boundaries due to the presence of RE. RE addition changed the morphology of the intergranular chromium carbides from continuous network shape to fragmentary distribution which was another cause for longer creep duration. These results strongly suggested that the effect of RE alloying played a crucial role in improving the creep rupture resistance.
