PSI - Issue 23

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Barbara Nasiłowska et al. / Procedia Structural Integrity 23 (2019) 583 –588 Nasiłowska B. / Structural Integrity Procedia 00 (2019) 000 – 000

586

Heat affected zone

WELD

27,16

3 μ m

500 μ m

Fig. 2. (a) heat affected zone in the joint made by the TIG method; (b) high-angle grain boundary

In result of double-sided shot peening of the tested elements the surface roughness increased: before shot-peening it was Ra = 8.812 µm, while after it Ra = 24.514 µm (Fig. 3).

a )

Base material

4. Analysis of the elemental composition of the surface layer

In-depth research of chemical composition of the upper layer was made using LIBS method. Acquisition of the stratigraphic LIBS spectra consisted in the execution of a certain number of laser cleaning pulses after which a proper pulse generated the plasma and its radiation spectrum was registered. On the basis of this LIBS spectrum a chemical composition at a certain layer depth was determined (Fig.4). In the

rid

face

1 mm

Fig. 3. Sample surface after upper layer shot peening

process of stainless (consisting of Cr~18%, Ni~10%, Si~1.8%, Mn~1.2%, Fe~69%) shot peening a transfer of microparticles coming from the stainless shot into the 5754 aluminium alloy surface down to the depth of 70 – 100 µm was observed. Below the selected fragments of LIBS spectrum taken in the upper layer from the depth of 1 µm with clear Ni, Fe, and Cr spectral line peaks coming from the shot (Fig.4a) and from the upper layer at the depth of about 70 – 100 µm. It should be noted that the intensity of Al spectral lines was the same for depths of 1 µm and 70 – 100 µm (Fig.4b).

 LIBS spectrum for 1 µm depth of the upper layer  LIBS spectrum for 70 - 100 µm depth of the upper layer

Fig. 4. (a) fragments of LIBS spectrum of the aluminium alloy upper layer for the wavelengths of 350 – 365 nm and (b) for 307 – 310 nm

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