稀土钇对奥氏体耐热钢高温拉伸性能影响及作用机制

Effect of Yttrium on Hot Tensile Properties of Austenitic Heat-Resistant Steel and Corresponding Mechanism

研究了钇对奥氏体耐热钢21Cr-11Ni-1.5Si-N的高温拉伸性能的影响及相关机制。在750-1 200℃,应变速率为0.005 s-1条件下进行了含与不含钇试样的热拉伸模拟试验及组织分析。结果表明：钇通过细化晶粒、强化晶界提高了试验钢在750-850℃的热塑性和抗拉强度;由于钇抑制了动态再结晶和再结晶晶粒长大,使得在850-1 050℃二者热塑性相当,而在1 050-1 200℃,含钇试验钢热塑性显著增加。另外,含钇试验钢经热加工后存有纤维组织;纤维状组织稳定性高,通过加热和动态再结晶也难以消除,而且其周围晶粒组织明显细小。

Effect of yttrium on hot tensile properties of a 21Cr-11Ni-1.5Si-N austenitic heat-resistant steel was investigated,the corresponding mechanism was discussed.The hot tensile simulation and microstructure of samples with and without yttrium were examined within the temperature range of 750-1 200 ℃ and the stain rate of 0.005 s-1.The results show that hot ductility and tensile strength of test steel are increased as the addition of yttrium can refine grain sizes and strengthen grain boundary over 750 ℃ to 850 ℃.Hot ductility of test steel with yttrium is close to that of test steel without yttrium at the temperature range of 850-1 050 ℃ and is improved significantly at temperature between 1 050 ℃ and 1 200 ℃,because yttrium can suppress dynamic recrystallization and recrystallized grain growth.Additionally,highly stable fibrous structures which are difficult to eliminate according to heat treatment and dynamic recrystallization are distributed in matrix of test steel with yttrium after hot working.A number of fine grains around fibrous structures have been observed.