Effect of the Difference in Strength of Hard and Soft Components on the Synergetic Strengthening of Layered Materials

Abstract

Heterogeneous structured materials achieve a combination of high strength and extreme ductility due to synergetic strengthening driven by conditions in the interfacial region. Although the origin of synergetic strengthening has been revealed to be strain incompatibility in the interfacial region, the effect of the strength difference between hard and soft phases on strengthening has not been investigated well. In the work reported in the present paper, the effect of the difference in strength of the hard and soft phases on synergetic strengthening was investigated by conducting in situ neutron diffraction tensile tests. As a result, it was determined that the dislocation density in a layered sheet of high Mn (HMn) steel/interstitial free (IF) steel is higher than that in a layered sheet of HMn/low carbon steel. The big difference in mechanical properties between HMn steel and IF steel induces a high stress gradient and results in additional dislocations. Because of the high dislocation density and large differences in mechanical property and anisotropy in the HMn/IF layered steel sheet, upper-bound rule-of-mixtures behavior occurs. Therefore, a great difference in the mechanical properties of hard and soft components increases the synergetic strengthening of heterogeneously structured materials. Graphic Abstract