低温下LF6合金及其焊接接头的拉伸性能和断口微观形貌

采用精密多功能低温静载材料实验机和扫描电子显微镜，系统研究了低温条件下LF6合金及其焊接接头的拉伸性能和断口微观形貌，分析讨论了低温对LF6合金及其焊接接头拉伸性能的影响规律。研究结果表明：低温对LF6合金及其焊接接头的拉伸性能具有显著影响。低温下，LF6合金焊接接头的强度和母材比较接近，但接头的延伸率只为母材的50％-70％。拉伸试样断口形貌分析结果显示，LF6合金及焊接接头的拉伸试样断口均为韧窝和撕裂棱混合型韧性断口，韧窝随温度的降低而变得细小、均匀。

TENSILE PROPERTIES AND FRACTURE MICRO-APPEARANCE OF LF6 ALLOY AND WELDED JOINT AT LOW TEMPERATURE SERVICE

The tensile properties and fracture micro-appearance of LF6 alloy and its welded joint at low temperature service have been studied by means of precise multifunction material testing system and scanning electron microscope (SEM), and the influences of low temperature on the tensile behavior of LF6 alloy and its welded joint are investigated. The results show that the tensile properties of LF6 alloy and its welded joint are greatly affected by low temperature. At low temperature, the strength of the welded joint nearly approaches that of the base metal, while its elongation is only 50% to 70% of the base alloy. The SEM observations show that the fracture surface of LF6 alloy and welded joint exhibits hybrid tough fracture of dimple and tear ridge, and dimple becomes tiny and uniform with the decrease of temperature.