The Impact Of The Hr2 Of Several Iron-based Alloy Phase Transition And Fracture Phenomena

HR2, as a new product of Fe-based materials, is widely used in many important engineering structures, but only shock Hugoniot data under higher pressure were measured in the study of it's dynamic characters. Whether phase transition in HR2 will occur under explosive loading like most Fe-based materials haven't been studied. In this paper dynamic behavior of HR2, whether the change in microstructure will dominate it's fracture behavior under moderate and low stress range is studied experimentally. DT2 was selected as a standard sample of Fe and Fe-based materials and one kind of stainless steel FeMnNi was selected as a comparing material.Shock-induced phase transition and fracture characters of HR2, DT2 and FeMnNi were studied by using one-stage gas gun and double-sensitivity VISAR. Typical triple-wave free surface velocity profiles with phase transition in DT2 and FeMnNi were recorded by VISAR. Spallation occurred in DT2 under homo-thickness symmetric impact when the pressure is higher than phase transition pressure, and no spallation occur when the pressure is lower than phase transition pressure. Shallow spallation occurred in FeMnNi under non-symmetric impact. For the two materials phase transition wave dominate the spalltion obviously. Only elastic-plastic double waves were observed in HR2 under moderate and low pressure, the phase transition wave hadn't been observed. The metallographic characters of recovered fragments had changed after impact in different way for the studied materials. Shock-induced phase transition arouse phenomenon appearance, and the corresponding physics are still not deeply studied.The dynamic behavior of HR2 and DT2 under explosive load were also studied in this paper, and the damage phenomena like spallation were analyzed. Apparent spallation fracture was found in wedgy DT2 sample under one-dimensional plane explosive loading, it's so different from E.A.Kozlov's result in damage appearance, which found spallation only on the local inclined plane of the sample under sliding detonation loading.The experiment results were partly numerical simulated. By adopting elastic-plastic constitutive equation excluding phase transition and a damage-level function model added in two-dimensional finite program DEFEL, the calculating results of HR2 are agree well with the experiment results. The numerical simulation of DT2 using one-dimensional POP program and three-section EOS including phase transition has been conducted. The results are also satisfactory, but more complete constitutive and fracture model is need in calculation dealing with unloading and spallation.The presented results are useful for understanding properties of HR2, DT2 and FeMnNi more deeply. From the experimental results it is seen that HR2 is different from other Fe-based materials and stainless steel, it hasn't shock-induced phase transition behavior displayed as typical triple-wave, and it's unloading fracture behavior will not be been influenced by this mechanism. It means shock-induced phase transitionisn't the dominant factor in HR2 under moderate and low stress range.