A new approach to understand the contribution of the microstructure in the fracture behavior of sintered steels

Understanding the effect of the microstructure on the fracture behavior in sintered steels has traditionally been done through analysis of the fracture surface (after fatigue-mode fracture) and some incipient trials of the analysis of the crack evolution through the microstructure after a tensile or impact test. There is no published work where the problem of understanding which of the phases present in a powder metallurgy steel contribute to the plastic deformation of the whole system, or which phase can avoid crack propagation during a continuous mechanical stress on the material. In this paper, a new approach to the problem is presented, combining three different techniques: 1) an in situ tensile test (inside the scanning electron microscope), where the initiation of the crack and its propagation have been monitored (the crack path can be seen during the test); 2) the digital image correlation technique, that allows identification of which individual micro-constituent contributes to the plastic deformation process during loading of the material, and to measuring this value, and 3) analysis of the fracture surface of the tested samples. The study has been performed on steels using materials with different microstructures (homogeneous and heterogeneous) obtained by various alloying techniques (mixing, prealloying, and a master-alloy approach).

A new approach to understand the contribution of the microstructure in the fracture behavior of sintered steels Articles