Some metallographic observations on the spalling of AISI 1060 steel by the formation of adiabatic shear bands

Abstract

The spalling of metals and alloys occurs by the localization of plastic deformation. The temperatures generated within the shear bands may induce recrystallization, solid state phase transformations and even melting. The objective of this research was to determine the effect of the hardness of an AISI 1060 steel on its resistance to spalling by ballistic impact and to record metallographically the evolution of the adiabatic shear bands as a result of repeated impact. The experimental results demonstrated that the resistance of AISI 1060 steel to spalling decreases as its hardness increases, and the layers of untempered martensite which form within the shear bands evolve discontinuously, i.e. the layer of martensite does not form during a single impact. The hardness of the martensite is consistent with the carbon content of the steel. Fractographic analysis of the smeared fracture surface of the spall fragments produced evidence of localized melting.