不同应变速率和缺口尺寸对316LN高温断裂行为的影响

Effect of Strain Rates and Notch Shape on High-temperature Fracture Behavior of 316LN Stainless Steel

针对核电设备零部件在热成形过程中产生的裂纹缺陷,采用热力学实验方法及微观组织观察,研究了应变速率ε(1、0.1、0.01、0.001s-1)和缺口半径(1、2、4 mm)对316LN不锈钢高温断裂行为的影响。结果表明,在同一温度(T=1200℃)、不同应变速率下,断裂应变ε_f随ε的减小而减小,微裂纹发生几率增加。此外,应变速率影响着断裂行为,较小ε下,以沿晶方式断裂;较大ε下,以沿晶和穿晶的混合方式断裂。同一温度同一应变速率(T=1200℃,ε=0.01 s-1)下,峰值应力σp和稳态应力σs随缺口半径的增大而降低;对比光滑和不同缺口半径试样断口微观组织,微裂纹随缺口半径的增大,发生的几率降低,而缺口半径对断裂模式没有影响。

Aiming at crack defects of the nuclear power equipment accessories occurring during hot forming, the effects of strain rates （1 s-1, 0.1 s-1, 0.01 s-1, 0.001 s-1） and notch radius （1, 2, 4 mm） on high-temperature fracture behaviors of 316LN stainless steel were investigated by using thermodynamic experimental method and observation of microstructure. The results show that the fracture stain 6fdecreases with strain rate decreasing and the risk of the appearance of micro cracks increases when the temperature is 1200℃ and the strain rate is various. Besides, the fracture mode is different with increasing strain rate. When strain rate is lower, the fracture mode is intergranular fracture. When the strain rate is higher, it is mixed fracture mode of intergranular and transgranular fracture. Keeping constant temperature and strain rate （T=1200 ℃, ε =0.01 s-1）, however, the peak stress σp and steady stress σs, decrease with the notch radius increasing. Compared with the fracture microstructure of smooth and different notch shape specimens, the risks of micro cracks decrease with the notch radius increasing, but the notch radius has no influence on the fracture mode.