Stainless Steel Dissimilar Metal Welds (SS DMW) between low-alloy steel 18MND5 and austenitic 316L stainless steel are critical junctions in the currently operating reactors because of their heterogeneous microstructure and mechanical properties. The presence of a narrow hard layer of carburized martensite and austenite in the ferritic-austenitic interface creates an important hardness gradient which affects the crack behavior of the SS DMW. In order to evaluate the plastic properties of this hard layer, a micro tensile testing method was developed. Tensile specimens of 15 x 80 x 6 μm were extracted from the martensitic and carburized austenitic layers by focused ion beam (FIB) micro-processing and tested using an in-situ tensile testing device. A platinum FIB deposition was used to measure local strain in the specimen during the test through digital image correlation (DIC). Isotropic elasto-plastic constitutive laws for the martensite and carburized austenite were obtained from the true strain-stress curves calculated from the micro-tensile tests. It was found that the corresponding plastic properties were in a good agreement with nanoindentation measurements and with values obtained from macroscopic tensile tests on crossweld specimens machined perpendicularly to the ferritic-austenitic interface and characterized using laser beam local diameter measurements. In-situ tensile testing is a promising technique for plastic behavior characterization of small scale materials and local hard layers in dissimilar metal welds.

中文翻译：

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不锈钢异种金属焊接界面的力学行为表征：渗碳马氏体和奥氏体的原位微拉伸试验

低合金钢 18MND5 和奥氏体 316L 不锈钢之间的不锈钢异种金属焊缝 (SS DMW) 是当前运行的反应堆中的关键连接点，因为它们具有异质的微观结构和机械性能。铁素体-奥氏体界面中渗碳马氏体和奥氏体的窄硬层的存在产生了一个重要的硬度梯度，这会影响 SS DMW 的裂纹行为。为了评估这种硬层的塑性，开发了一种微拉伸测试方法。通过聚焦离子束 (FIB) 微加工从马氏体和渗碳奥氏体层中提取 15 x 80 x 6 μm 的拉伸试样，并使用原位拉伸测试设备进行测试。在测试过程中，通过数字图像相关 (DIC) 使用铂 FIB 沉积来测量试样中的局部应变。马氏体和渗碳奥氏体的各向同性弹塑性本构法则是从微拉伸试验计算的真实应变-应力曲线中获得的。发现相应的塑性性能与纳米压痕测量以及从垂直于铁素体-奥氏体界面加工的交叉焊接试样的宏观拉伸试验中获得的值非常一致，并使用激光束局部直径测量进行表征。原位拉伸试验是一种很有前途的技术，可用于表征异种金属焊缝中小尺寸材料和局部硬层的塑性行为。马氏体和渗碳奥氏体的各向同性弹塑性本构法则是从微拉伸试验计算的真实应变-应力曲线中获得的。发现相应的塑性性能与纳米压痕测量以及从垂直于铁素体-奥氏体界面加工的交叉焊接试样的宏观拉伸试验中获得的值非常一致，并使用激光束局部直径测量进行表征。原位拉伸试验是一种很有前途的技术，可用于表征异种金属焊缝中小尺寸材料和局部硬层的塑性行为。马氏体和渗碳奥氏体的各向同性弹塑性本构法则是从微拉伸试验计算的真实应变-应力曲线中获得的。发现相应的塑性性能与纳米压痕测量以及从垂直于铁素体-奥氏体界面加工的交叉焊接试样的宏观拉伸试验中获得的值非常一致，并使用激光束局部直径测量进行表征。原位拉伸试验是一种很有前途的技术，可用于表征异种金属焊缝中小尺寸材料和局部硬层的塑性行为。发现相应的塑性特性与纳米压痕测量值以及从垂直于铁素体-奥氏体界面加工的交叉焊接试样的宏观拉伸试验中获得的值非常一致，并使用激光束局部直径测量进行表征。原位拉伸试验是一种很有前途的技术，可用于表征异种金属焊缝中小尺寸材料和局部硬层的塑性行为。发现相应的塑性特性与纳米压痕测量值以及从垂直于铁素体-奥氏体界面加工的交叉焊接试样的宏观拉伸试验中获得的值非常一致，并使用激光束局部直径测量进行表征。原位拉伸试验是一种很有前途的技术，可用于表征异种金属焊缝中小尺寸材料和局部硬层的塑性行为。