Abstract
The void closure mechanism during the roll-bonding process was investigated using a multiscale approach, which includes contact deformation at the macro-scale and atomic bonding at the micro-scale. The closure process of the voids was observed using roll-bonding tests of 304 stainless steel/Q235 carbon steel. A finite element model was built to simulate the macroscopic deformation process of 304/Q235 material, and a molecular dynamics model established to simulate the deformation process of the microscopic rough peaks. The closure law and mechanism of interface voids at the macro- and micro-scales were studied. The results show that the closure rate of interface voids decreases with the decrease in the average contact stress during the contact deformation process. In the atomic bonding process, the void closure rate is slow in the elastic deformation process. The ordered atoms near the interface become disordered as plastic deformation occurs, which increases the void closure rate and hinders dislocation propagation through the interface, resulting in significant strengthening effects via plastic deformation. Ultimately, a perfect lattice is reconstructed with void healing. In addition, the interface morphology after roll-bonding at the macro scale was determined by the morphology of the 304 steel with larger yield strength ratio, while the interface morphology at the micro-scale was mainly determined by the morphology of the Q235 steel with a higher yield strength.
Highlights
Austenitic stainless steel, exhibiting good corrosion resistance at high temperatures, is widely used in the petrochemical industry, aviation, shipping, as well as other industries
To study the interfacial deformation process of corresponding rough peaks and the interfacial mechanism of void closure, The bonding rate is an important index for evaluating the bonding quality the of increases, thefinite plastic deformation of the metal in the interface region causes the voids to shrink were into macro‐scale model the micro‐scale molecular dynamics composites
As the temperature rises from normal temperature to approximately 700 °C, the Q235 carbon steel with a body‐centered cubic structure (BCC) will be austenitized and transformed into the face-centered cubic structure (FCC) structure
Summary
Austenitic stainless steel, exhibiting good corrosion resistance at high temperatures, is widely used in the petrochemical industry, aviation, shipping, as well as other industries. When the two materials are stacked, only the asperities on the surface contact each other, forming a row of irregular voids, which gradually shrink until completely closed during the roll-bonding process. The whole roll-bonding process can be regarded as the closure process of interface voids on various scales. Chen and Ke [13] studied the diffusion bonding process of Cu/Al with rough surfaces at different temperatures, and divided the bonding process into three stages. The voids on the Al side are closed due to the elemental diffusion in the friction process, while the voids on the Ni side are closed in the forging process due to the deformation of the interface These studies mainly focus on the void closure and diffusion process of bimetallic surfaces with rough surfaces, but lack research on the interfacial void closure behavior of bimetallic surfaces during roll-bonding. The void closure behavior on different scales was studied by the finite element method and molecular dynamics method
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