Liu Mengying, Jiang Lai, Demkowicz Michael J
Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843-3003, USA.
Physics and Engineering Department, Washington and Lee University, 204 W Washington Street, Lexington, VA 24450, USA.
Sci Adv. 2024 Jul 19;10(29):eado2118. doi: 10.1126/sciadv.ado2118. Epub 2024 Jul 17.
We conduct in situ tensile straining experiments to investigate the role of hydrogen and slip in crack initiation in nickel-based alloy 725. Our experiments reveal no tendency for hydrogen to enhance localized slip and no necessity of slip for crack initiation. We use electrochemical charging to introduce hydrogen into samples, melt extraction to measure hydrogen content, and digital image correlation to analyze localized plastic strains during in situ tensile tests in a scanning electron microscope. Cracks initiate both in regions with and without nearby localized slip. Moreover, the fraction of cracks initiating with no nearby slip is greater at higher hydrogen content. Slip-assisted crack initiation generally occurs at locations where intergranular slip is arrested, especially at intersections of slipping coherent twin boundaries with thin twin lamellae. Cracks that initiate without nearby slip occur at a wider variety of microstructural features, including inclusions, triple junctions, and surface flaws.
我们进行原位拉伸应变实验，以研究氢和滑移在镍基合金725裂纹萌生中的作用。我们的实验表明，氢没有增强局部滑移的趋势，并且裂纹萌生也不需要滑移。我们采用电化学充氢法将氢引入样品中，用熔体萃取法测量氢含量，并利用数字图像相关技术在扫描电子显微镜下原位拉伸试验期间分析局部塑性应变。裂纹在有和没有附近局部滑移的区域均会萌生。此外，在较高氢含量下，在没有附近滑移情况下萌生的裂纹比例更大。滑移辅助裂纹萌生通常发生在晶间滑移受阻的位置，特别是在滑移的相干孪晶界与薄孪晶片层的相交处。在没有附近滑移情况下萌生的裂纹出现在更广泛的微观结构特征处，包括夹杂物、三叉晶界和表面缺陷。
