In Situ Investigation of Microscale Deformation Mechanisms of Individual Phases in Silicon Stainless Steel with Varied Si Content

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Abstract
This research aims to understand the influence of silicon content (1.79 and 6.06 wt% Si) on the microscale deformation behavior of stainless steels for potential cryogenic applications, by means of in situ tensile testing within a scanning electron microscope. The investigation focuses on how silicon‐induced solid solution strengthening and ferrite phase stabilization affect mechanical response through strain partitioning between γ‐austenite and δ‐ferrite phases. As the silicon content increases, the microstructure transforms from a single‐phase γ to a dual‐phase microstructure comprising both γ and δ. Quantitative analysis of local misorientation, image quality, and deformed volume fraction reveals that the δ‐phase in the high‐silicon alloy exhibits delayed slip line formation and higher resistance to plastic deformation. This is further supported by nanohardness measurements, where the γ and δ phases in the high‐silicon alloy show significantly higher values (6.06% Si, γ ≈ 3.4 GPa; δ ≈ 4.96 GPa) compared to the γ‐phase in the low‐silicon alloy (1.79% Si, γ ≈ 2.7 GPa). Orientation mapping and misorientation profiles indicate that deformation occurs through heterogeneous mechanisms, including both slip and twinning, providing critical insights into the strain partitioning behavior and texture evolution in stainless steels.

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