Investigation of deformation mechanisms during bending and microstructure characterization of bended contact materials with laser-structured surfaces

The current study presents an investigation of the mechanical response and surface topography in the case of a copper based alloy bent at 60°, 90°, and 120°, and formed at pressures from 6 to 30 bars. Three different types of specimens were prepared: an uncoated substrate, a coated sample in the as-received state, and a coated sample which had undergone aging and conversion of the deposited tin coating to intermetallic phases. In addition, some samples were processed by direct laser surface patterning (DLIP) to investigate its effect on formability and stress distribution. Bending and shaping at various angles of applied pressure were involved in the research methodology. Characterization of the microstructure and coating behavior was done through optical and scanning electron microscopy. The experimental data were analyzed using the concepts of contact mechanics to determine how the surface stress and deformation behavior were influenced by coating phase advancement. Furthermore, the surfaces of some samples were examined for digital image correlation (DIC) pictures after the bending and shaping processes to study the distribution of stress and strain and also assess the effects of the surface laser pattern and coating layer properties. The results indicated that the pure tin coating acted as a ductile and lubricating interlayer, which reduced friction and stress concentration and improved strain uniformity during deformation. Aging caused the transformation of tin to Cu6Sn5 and Cu3Sn intermetallics, significantly increasing the surface hardness and adhesion but substantially degrading the ductility, leading to localized cracking under high strain. Shaping experiments showed that lower shaping loads and more homogeneous deformation were achieved for substrate samples. In contrast, the aged intermetallic coated samples showed higher strength but limited formability owing to their brittle interfacial fracture. Also, DLIP improved the adhesion in ductile coatings by refining the stress distribution and deferring the delamination. However, in the coated sample in aged condition, laser induced topography acted like a stress concentrator, thereby enhancing microcrack initiation along the coating substrate interface. In summary, the study concludes that the coating phase and microstructure strongly influence the mechanical and tribological behavior of the cu-sn systems. In this regard, balanced mechanical and functional properties can be achieved by combining pure tin coatings with controlled thermal aging and laser surface engineering. The findings of this work contribute to the design and development of high performance conductive coatings and surface layers that might be applied in advanced electronic packaging, automotive systems, and precision mechanical components.