Novel Methods for Recording Stress-Strain Curves in Proton Irradiated Material

Area of Science:

• Materials Science
• Nuclear Engineering
• Mechanical Engineering

Background:

• Proton irradiation is a common substitute for neutron irradiation in materials testing.
• The shallow depth of proton-irradiated layers (<50 μm) complicates mechanical property assessment.
• Accurate mechanical data as a function of irradiation level is critical for material performance evaluation.

Purpose of the Study:

• To develop and validate novel methodologies for characterizing the mechanical behavior of thin proton-irradiated surface layers.
• To overcome the challenge of shallow irradiation depths in obtaining reliable stress-strain data.
• To accurately measure the irradiation-induced shift in yield strength, strain hardening, and tensile strength.

Main Methods:

• In-situ loading experiments combining X-ray diffraction and digital image correlation on near-surface regions.
• Manufacturing of small-scale tensile specimens using high-speed focused ion beam (FIB) milling with Xe+ Plasma-FIB (PFIB) to isolate the irradiated volume.
• Recording stress-strain curves to analyze uniaxial flow behavior.

Main Results:

• Both developed methodologies successfully recorded the early stages of uniaxial flow behavior in proton-irradiated SA-508-4N ferritic steel.
• The techniques provide accurate measurements of stress and strain, isolating the effects of the irradiated layer.
• Quantification of irradiation-induced shifts in yield strength, strain hardening, and tensile strength was achieved.

Conclusions:

• The developed in-situ and small-scale specimen techniques are effective for characterizing the mechanical properties of thin proton-irradiated layers.
• These methods enable accurate assessment of material behavior under irradiation, crucial for nuclear and other applications.
• The findings contribute to a better understanding of irradiation effects on the mechanical integrity of materials like SA-508-4N steel.