He Hanbing, Forouzan Farnoosh, Volpp Joerg, Robertson Stephanie M, Vuorinen Esa
Division of Material Science, Luleå University of Technology, 971 87 Luleå, Sweden.
Division of Product and Production Development, Luleå University of Technology, 971 87 Luleå, Sweden.
Materials (Basel). 2021 Jan 19;14(2):456. doi: 10.3390/ma14020456.
The aim of this work was to investigate the microstructure and the mechanical properties of laser-welded joints combined of Dual Phase DP800 and DP1000 high strength thin steel sheets. Microstructural and hardness measurements as well as tensile and fatigue tests have been carried out. The welded joints (WJ) comprised of similar/dissimilar steels with similar/dissimilar thickness were consisted of different zones and exhibited similar microstructural characteristics. The trend of microhardness for all WJs was consistent, characterized by the highest value at hardening zone (HZ) and lowest at softening zone (SZ). The degree of softening was 20 and 8% for the DP1000 and DP800 WJ, respectively, and the size of SZ was wider in the WJ combinations of DP1000 than DP800. The tensile test fractures were located at the base material (BM) for all DP800 weldments, while the fractures occurred at the fusion zone (FZ) for the weldments with DP1000 and those with dissimilar sheet thicknesses. The DP800-DP1000 weldment presented similar yield strength (YS, 747 MPa) and ultimate tensile strength (UTS, 858 MPa) values but lower elongation (EI, 5.1%) in comparison with the DP800-DP800 weldment (YS 701 MPa, UTS 868 MPa, EI 7.9%), which showed similar strength properties as the BM of DP800. However, the EI of DP1000-DP1000 weldment was 1.9%, much lower in comparison with the BM of DP1000. The DP800-DP1000 weldment with dissimilar thicknesses showed the highest YS (955 MPa) and UTS (1075 MPa) values compared with the other weldments, but with the lowest EI (1.2%). The fatigue fractures occurred at the WJ for all types of weldments. The DP800-DP800 weldment had the highest fatigue limit (348 MPa) and DP800-DP1000 with dissimilar thicknesses had the lowest fatigue limit (<200 MPa). The fatigue crack initiated from the weld surface.
这项工作的目的是研究双相DP800和DP1000高强度薄钢板组合的激光焊接接头的微观结构和力学性能。进行了微观结构和硬度测量以及拉伸和疲劳试验。由厚度相似/不同的相似/不同钢材组成的焊接接头（WJ）由不同区域组成，并表现出相似的微观结构特征。所有焊接接头的显微硬度趋势是一致的，其特征是在硬化区（HZ）硬度值最高，在软化区（SZ）硬度值最低。DP1000和DP800焊接接头的软化程度分别为20%和8%，DP1000焊接接头组合中SZ的尺寸比DP800的更宽。所有DP800焊件的拉伸试验断裂都位于母材（BM）处，而DP1000焊件以及不同板材厚度的焊件的断裂发生在熔合区（FZ）。与DP800-DP800焊件（屈服强度701MPa、抗拉强度868MPa、伸长率7.9%）相比，DP800-DP1000焊件的屈服强度（YS，747MPa）和抗拉强度（UTS，858MPa）值相似，但伸长率（EI，5.1%）较低，DP800-DP800焊件的强度性能与DP800的母材相似。然而，DP1000-DP1000焊件的伸长率为1.9%，与DP1000的母材相比要低得多。与其他焊件相比，不同厚度的DP800-DP1000焊件的屈服强度（955MPa）和抗拉强度（1075MPa）值最高，但伸长率最低（1.2%）。所有类型焊件的疲劳断裂都发生在焊接接头上。DP800-DP800焊件的疲劳极限最高（348MPa），不同厚度的DP800-DP1000焊件的疲劳极限最低（<200MPa）。疲劳裂纹从焊缝表面开始。
