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金属学报  2024, Vol. 60 Issue (2): 211-219    DOI: 10.11900/0412.1961.2022.00041
  研究论文 本期目录 | 过刊浏览 |
微米级选区激光熔化316L不锈钢的拉伸力学性能
张楠1,2, 张海武2, 王淼辉1,2()
1 中机新材料研究院(郑州)有限公司 郑州 450001
2 中国机械科学研究总院集团有限公司 北京 100044
Tensile Mechanical Properties of Micro-Selective Laser Melted 316L Stainless Steel
ZHANG Nan1,2, ZHANG Haiwu2, WANG Miaohui1,2()
1 China Machinery Institute of Advanced Materials Co. Ltd., Zhengzhou 450001, China
2 China Academy of Mechanical Science and Technology Group Co. Ltd., Beijing 100044, China
引用本文:

张楠, 张海武, 王淼辉. 微米级选区激光熔化316L不锈钢的拉伸力学性能[J]. 金属学报, 2024, 60(2): 211-219.
Nan ZHANG, Haiwu ZHANG, Miaohui WANG. Tensile Mechanical Properties of Micro-Selective Laser Melted 316L Stainless Steel[J]. Acta Metall Sin, 2024, 60(2): 211-219.

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摘要: 

为辅助理解金属材料高精密增材制造成形机理,本工作利用微米级选区激光熔化(micro-selective laser melting,M-SLM)技术制备了316L不锈钢,对其拉伸性能及断裂行为进行了研究,并对断后横向和纵向拉伸试样显微组织和断口形貌进行了表征与分析,对近断面塑性变形区的晶粒取向、晶界特征分布等进行了电子背散射衍射(EBSD)分析。结果表明:M-SLM制备316L不锈钢晶粒内部存在尺寸为100~300 nm的胞状组织结构,拉伸断口呈韧窝状,窝口直径80~500 nm,这使得316L不锈钢的横向平均抗拉强度达692.1 MPa,纵向平均断后延伸率达54.6%,明显优于传统SLM技术制备的316L不锈钢。M-SLM制备316L不锈钢在拉伸过程中奥氏体Σ3孪晶界的出现与晶粒取向有关,其在取向接近<111>的晶粒中较易出现。进一步分析指出,Σ3晶界的出现阻断了特殊晶界网络的连通性。通过基于EBSD的矩形截面法对共格Σ3 (Σ3c)和非共格Σ3 (Σ3ic)晶界进行了统计分析,显示316L横向拉伸试样近断口区的Σ3cΣ3ic晶界数量百分比分别约为43%和57%,而纵向拉伸试样近断口区的Σ3c晶界数量百分比提高至约70%。Σ3c孪晶界的增加使得总晶界能降低,是导致M-SLM制备316L不锈钢纵向拉伸强度普遍低于横向拉伸强度的原因。

关键词 微米级选区激光熔化316L不锈钢拉伸性能Σ3晶界孪晶    
Abstract

Compared with selective laser melting (SLM), the micro-SLM (M-SLM) technology offers the advantages of small spot diameter (< 20 μm), high forming precision (20-50 μm), and surface roughness (Ra) of up 1 μm, which implies that the M-SLM technology provides great potential for promotion and application in communication electronics, biomedical, and other fields in the future. In this work, 316L stainless steel was prepared using M-SLM, and its tensile properties and fracture behavior were studied. The microstructures of transverse and longitudinal tensile specimens were also investigated. In addition, the fracture morphology was characterized and analyzed, and the grain orientation and grain-boundary-characteristic distribution in the near-section plastic-deformation zone were further analyzed using electron backscatter diffraction (EBSD). The results showed that the 316L stainless steel prepared by M-SLM had a cellular structure with a size of 100-300 nm inside the grains. The tensile fracture was dimple-shaped, and the average dimple diameter was 80-500 nm, which allowed the transverse average tensile strength of the 316L stainless steel to reach 692.1 MPa, the longitudinal average elongation after fracture was 54.6%, which were obviously better than that of the 316L stainless steel prepared using traditional SLM. The appearance of austenite Σ3 twin boundaries in the stretching process of the 316L stainless steel prepared by M-SLM was related to the grain orientation, which could more likely appear in grains with an orientation close to <111>. Further analysis indicated that the appearance of Σ3 grain boundaries blocked the connectivity of the special grain-boundary network. Statistical analysis of the coherent Σ3 (Σ3c) and incoherent Σ3 (Σ3ic) grain boundaries using the EBSD-based rectangular-section method revealed that the amount percentages of Σ3c and Σ3ic in the near-fracture region of the 316L transverse tensile specimen were approximately 43% and 57%, respectively. Meanwhile, the amount percentage of Σ3c in the same region of the 316L longitudinal tensile specimen increased to approximately 70%. The increase in the coherent Σ3c twin boundary reduced the total grain-boundary energy, which explained why the longitudinal tensile strength of the 316L stainless steel prepared by M-SLM was generally lower than the transverse tensile strength.

Key wordsmicro-selective laser melting    316L stainless steel    tensile property    Σ3 boundary    twinning
收稿日期: 2022-02-14     
ZTFLH:  TG142  
基金资助:国家自然科学基金项目(51975240);北京市自然科学基金项目(2222093);中国机械科学研究总院集团技术发展基金项目(812201Q9)
通讯作者: 王淼辉,wangmh0103@163.com,主要从事金属增材制造技术研究
Corresponding author: WANG Miaohui, professor, Tel: (010)60603546, E-mail: wangmh0103@163.com
作者简介: 张 楠,男,1983年生,高级工程师,博士
图1  微米级选区激光熔化(M-SLM)制备拉伸试样尺寸示意图
图2  316L不锈钢粉末的SEM像
图3  M-SLM成形316L不锈钢的XRD谱
图4  M-SLM成形316L不锈钢横向和纵向显微组织的SEM像
图5  M-SLM成形316L不锈钢工程应力-应变曲线
DirectionRm / MPaδ / %UT / (J·cm-3)
Transverse692.132.0210.6
Longitudinal642.354.6331.9
表1  M-SLM成形316L不锈钢不同增材方向的拉伸性能
图6  M-SLM和传统SLM成形316L不锈钢拉伸力学性能比较
图7  M-SLM成形不同方向316L不锈钢拉伸断口形貌的SEM像
图8  M-SLM成形316L不锈钢横向和纵向试样拉伸断裂区微观组织EBSD分析(a, d) inverse pole figures (IPFs)(b, e) special grain boundary distribution maps(c, f) deformed metal distribution maps
图9  M-SLM成形316L不锈钢纵向试样拉伸断裂区孪晶晶粒标准取向三角图
图10  微矩形截面法判定图8b中圈圈区域Σ3晶界的示意图(a) Σ3 grain boundary(b) pole figure of {111} crystal form
No.φ / (o)TypeNo.φ / (o)Type
8b-1+4IC8e-1+8IC
8b-2-2C8e-2-1C
8b-3+6IC8e-3-2C
8b-4+2C8e-40C
8b-50C8e-5-2C
8b-6-6IC8e-6+4IC
8b-7+4IC8e-7-3C
8b-8-1C8e-8+3C
8b-9+7IC8e-9-9IC
8b-10-3C8e-10-2C
8b-11-5IC8e-11-7IC
8b-12+3C8e-12-2C
8b-13-7IC8e-13+1C
8b-14+2C8e-14-4IC
8b-15-6IC8e-15+7IC
8b-16-3C8e-16+1C
8b-17+9IC8e-17-2C
8b-18-6IC8e-18+5IC
8b-19+3C8e-19+1C
8b-20+4IC8e-20-2C
8b-21+1C8e-21-3C
8b-22-5IC8e-22+5IC
8b-23+6IC8e-23+1C
8b-24-4IC8e-240C
8b-25-1C8e-25-1C
8b-260C8e-26+2C
8b-27+7IC8e-27-2C
8b-28-5IC8e-28+3C
8b-29-6IC8e-29+1C
8b-30-2C8e-30+4IC
表2  图8b和e中Σ3晶界分析结果
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