135 / 2021-04-10 18:21:40

微区原位锻造复合增材制造Al-Mg4.5Mn合金缺陷致疲劳失效研究

增材制造；微区原位锻造；Al-Mg4.5Mn；疲劳性能评价；同步辐射

微区原位锻造复合增材制造Al-Mg4.5Mn合金缺陷致疲劳失效研究

虞雨洭，吴圣川^*，谢成

(西南交通大学 牵引动力国家重点实验室 四川 成都 610031)



摘 要：微区原位锻造复合增材制造技术（Hybrid in situ rolled wire + arc additive manufacturing，HRAM）实现了增-等-减材与调质集成制造，可一体化超短流程直接打印出大型高性能锻件。针对HRAM及丝弧增材制造（Wire and arc additive manufacturing，WAAM）Al-Mg4.5Mn合金，开展缺陷限度和疲劳寿命预测研究。基于同步辐射X射线显微计算机断层扫描技术，采用极值统计方法定量表征了试样缺陷几何特征（密度、形态、分布、尺寸等），结合三维成像大数据仿真分析缺陷的局部应力集中现象；基于自主研制的高分辨三维成像原位试验机观测了疲劳试验过程中HRAM成形Al-Mg4.5Mn合金内的缺陷演化行为；借助高周疲劳试验及断口分析，探索HRAM铝合金的疲劳性能及相关失效模式。绘制了材料的概率疲劳寿命（P-S-N）曲线，引入Murakami提出的缺陷尺寸√area，借助修正的NASA/FLACGRO（NASGRO）模型，结合微观组织表征及疲劳裂纹扩展速率试验，对含缺陷材料进行高周疲劳寿命预测。结果表明，HRAM技术能够有效降低制备铝合金样品内的缺陷数量和尺寸，同时实现晶粒细化并提高材料塑性；未熔合缺陷应力集中系数比气孔高约40%；材料的疲劳失效均源于表面或近表面缺陷，缺陷的不均匀分布是造成高周疲劳寿命分散性较大的主要原因；成像结果进一步表明疲劳裂纹在扩展过程中存在局部加速及止裂现象；寿命预测结果均位于P-S-N曲线范围内且偏于保守。

关键词：增材制造；微区原位锻造；Al-Mg4.5Mn；疲劳性能评价；同步辐射

中图分类号：        文献标志码：           文章编号：

Defect-correlated fatigue resistance of hybrid in situ rolled wire + arc additively manufactured AL-MG4.5MN alloy

YU Yukuang  WU Shengchuan^*  XIE Cheng

(State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031)



Abstract：Hybrid in situ rolled wire + arc additive manufacturing (HRAM) is a potential 3D printing method that combines traditional wire and arc additive manufacturing (WAAM) with in situ micro-rolling. Here, the manufacturing defects and mechanical and fatigue strength were explored for an HRAM- and WAAM-processed Al-Mg4.5 Mn alloy. The results show that advanced HRAM can result in significant grain refinement and enhance the material failure resistance compared with standard WAAM. High-resolution X-ray tomography was adopted to identify the defect density, morphology, distribution, and size, which showed that the defect population and size produced by HRAM were considerably lower than those produced by WAAM. Based on high-cycle fatigue tests, fatigue failure was observed entirely from metallurgical defects. Finite element simulations of the defect images based on computed tomography scans showed that lack-of-fusion defects are more dangerous than gas porosity in terms of increasing the local stress. Finally, the defect-controlled fatigue lifetime was predicted by combining the peaks-over-threshold method with a modified NASGRO model.

Key words：Additive manufacturing; In situ micro-rolling; Al-Mg4.5Mn alloy; Fatigue performance evaluation; Synchrotron tomography.