Mahdieh Safyari 교수

An attractive approach to mitigate hydrogen embrittlement (HE) is to use nano-sized particles to immobilize hydrogen. However, atomic scale relationship between different particle-matrix characteristics in aluminum alloys and the susceptibility to HE is unknown. In this study, effects of interactions between various interfaces and hydrogen in aluminum alloys are investigated using a comprehensive multiscale experimental and simulation-based approach that includes atomic scale observations, simul

The effect of ultrasonic shot peening on the environmental hydrogen embrittlement behavior of the 7075-T6 aluminum alloy is investigated. The 7075-T6 tensile specimens were treated by ultrasonic shot peening for 50 s. Surface residual stress and the depth of residual stress under the surface were evaluated using an X-ray diffractometer. Then, the specimens were tensile tested in humid air and dry nitrogen gas by the slow strain rate technique. The results showed that the ultrasonic shot-peened s

In this work, atom probe tomography technique is used to investigate how wire arc additive manufacturing (WAAM) changes the nanochemistry of nanoprecipitates and grain boundaries after peak aging of a high strength Al-Zn-Mg-Cu alloy. The effect of change in nanochemistry of nanoprecipitates on the hydrogen embrittlement of the additively manufactured aluminum alloy is investigated using a three-point bending test in humid air. The results show that the unique in-process heat treatment during WAA

The initial growth of a porous alumina layer and the hydrogen absorption during galvanostatic anodization were studied using high-resolution electron microscopy, thermal desorption spectroscopy, and hydrogen microprint technique. The nanostructure of the alumina layer depends strongly on the anodization time. The embryo of pores grows as the thickness of the oxide layer increases, and a porous alumina layer is formed until the voltage reached its maximum value. Eventually, the connected pores to

Low-carbon martensitic steels are candidate materials for different hydrogen applications. Hydrogen embrittlement (HE) of the steels can be mitigated by designing trap site characteristics. In this study, the different capacities of hydrogen trapping, and reversibility of the trap sites are studied to reveal the extent of HE susceptibility of the steels and H-induced crack initiation and propagation mechanisms. The trap sites in Ti-contained and Mo-contained martensitic steels were identified an

Wire arc additive manufacturing (WAAM) leads to a unique nano/microstructure. The combination of multiscale experimental and numerical analyses firstly shows that the intrinsic heat treatment during WAAM leads to an unusual depletion of Mg near the grain boundaries. During the WAAM process, a high dislocation density leads to formation of sub-grains and high-angle grain boundaries (HAGBs). It is revealed that the uniformly distributed micropores formed during the WAAM are strong hydrogen traps.