Effects of layer thickness on deformation-induced martensite transformation and tensile behaviors in a multilayer laminate

Multilayer laminates with a 304 stainless steel as surface layers and with a low C steel and a medium-Mn steel as alternating central layers have been developed in the present study. The number of interfaces and the layer thickness have been varied, while maintaining the similar microstructures for each layer. The uniform elongation is observed to increase from 10.1% to 37.8%, and the product of strength and elongation is found to increase from 13.6 GPa·% to 36.8 GPa·% monotonically with decreasing layer thickness in multilayer laminates, while the yield stress remains almost constant. Firstly, deformation-induced martensite transformation is significantly promoted with decreasing layer thickness. Secondly, the more interfaces can induce the accumulation of higher density of geometrically necessary dislocations, resulting in better mechanical properties. Lastly, the main cracks nucleate and propagate at the interfaces of low C steel layers and medium Mn steel layers, thus the samples with smaller layer thickness have more interfaces and require more energy consumption during the micro-fracture process, resulting in better tensile performance.