论文标题
CRMNFECONI高熵合金的循环塑性和疲劳损伤由激光粉末融合制造
Cyclic plasticity and fatigue damage of CrMnFeCoNi high entropy alloy fabricated by laser powder-bed fusion
论文作者
论文摘要
CRMNFECONI高渗透合金具有高度可打印,并且具有巨大的结构应用潜力。但是,在先前的研究中,没有关于环状可塑性和疲劳损害的重大讨论。这项研究提供了对印刷过程,固化微观结构,环状可塑性和疲劳损伤演变之间联系的重要见解。基于热力学的预测(通过扫描透射电子显微镜(STEM)能量色散X射线光谱(EDX)验证,表明CR,CO和FE分区分配给凝固细胞的核心,而MN和Ni在所有考虑的打印参数中均与细胞边界。发现脱位滑动和变形孪生均应导致单调载荷下的塑性变形。然而,发现前者是循环可塑性的单个主要机制。表面饰面有助于实质上延迟裂纹的启动,并导致缺乏融合孔隙度成为裂纹启动的主要来源。最重要的是,扫描策略显着影响谷物排列和谷物尺寸,从而对疲劳裂纹的传播产生明显影响。特别是,由于柱状晶粒最多,并且沿裂纹传播路径的晶粒边界最小的晶粒间距最大,在曲折扫描策略中看到了最高的电阻裂纹传播。
The CrMnFeCoNi high-entropy alloy is highly printable and holds great potential for structural applications. However, no significant discussions on cyclic plasticity and fatigue damage in previous studies. This study provides significant insights into the link between print processes, solidification microstructure, cyclic plasticity and fatigue damage evolution in the alloy fabricated by laser powder bed fusion. Thermodynamics-based predictions (validated by scanning transmission electron microscopy (STEM) energy dispersive X-ray spectroscopy (EDX)) showed that Cr, Co and Fe partition to the core of the solidification cells, whilst Mn and Ni to the cell boundaries in all considered print parameters. Both dislocation slip and deformation twinning were found to be responsible for plastic deformation under monotonic loading. However, the former was found to be the single dominant mechanism for cyclic plasticity. The surface finish helped to substantially delay the crack initiation and cause lack-of-fusion porosity to be the main source of crack initiation. Most significantly, the scan strategies significantly affect grain arrangements and grain dimensions, leading to noticeable effects on fatigue crack propagation; in particular, the highest resistance crack propagation was seen in the meander scan strategy with 0° rotation thanks to the most columnar grains and the smallest spacing of grain boundaries along the crack propagation path.