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Top1. Introduction
Islands-Matrix-Dual-phase steel (I-M-DP steel) is a high-strength steel that has ferrite as a soft-matrix and hard martensite-islands combined microstructure. The microstructure of dual phase steel consists of ferrite and martensite phases, where ferrite is a matrix and martensite is an island. The processing of Islands-Matrix-Dual-phase steel is done by quenching followed by intercritical annealing (Krajewski and Nowacki, 2014; Darabi et al., 2017; Belgasam and Zbib, 2018). Application in crash-relevant components of vehicle bodies I-M-DP steels are given the high energy absorption capacity (Paul and Kumar, 2012; Belgasam and Zbib, 2018), demanding a combination of strength-ductility, tensile properties (Paul and Kumar, 2012; Paul, 2013) and fatigue properties (Paul et al., 2015a,b; Rana et al.,2019a) of binary phases dual phase steels are particularly well suited for automotive structural and safety parts such as longitudinal beams, cross members and reinforcements. The use of this type of steel is not only increasing in the automobile industry but is also aiming towards a better group of high ductility and strength which is further needed with the decrease in vehicle weight, so that fuel consumption also can be reduced. In view of that, car and steelmakers are concerned in detailed forecasting the effect of various microscopic factors as well as optimizing microstructural properties for the application in crash-relevant components of vehicle body’s material as I-M-DP steel (Sirinakorn et al., 2014; Belgasam and Zbib, 2017). During the processing route of I-M-dual phase steels, non-metallic inclusions may exist in steel microstructure (Uthaisangsuk et al., 2011). Rana et al., 2019b investigated the outfall of stress field mechanisms using a numerical model due to isotropic elastic inhomogeneity in structural metal under uniaxial tensile stress for soft and hard-inclusions in a matrix. The flow behavior of the I-M-DP steel is utterly dependent on the microstructure parameters. Volume fraction (VFs) and grain sizes (GS) of different phases are also played an important contribution in the mechanical properties of such steel (Paul et al., 2015). Such steel sheets are used in automotive inner panels and body-in-white components which are further required for the design flexibility with respect to various parametric considerations (Paul and Kumar, 2012). Nevertheless, steel suppliers strive to further enhance the mechanical properties of Islands-Matrix-dual phase steels by optimizing their microstructure. Binary phases steels with different grades can be produced by controlling intercritical temperature and the compositions of the constituent (Krajewski and Nowacki, 2014; Belgasam and Zbib, 2018). According to Uthaisangsuk et al., 2011 and Samei et at., 2014 in experiments, concurrently two failure modes were found one cleavage and another dimple fracturing. The de-bonding of the island from ferritic-matrix or the island cracking was formed in the form of void nucleation. On other hand, plastic deformation starts at matrix grains. Hence, the state of yielding initiation of islands-matrix-dual phase steel is mainly governed by the matrix properties. At the time of plastic deformation initiation in the matrix of dual-phase steel, other phase islands that time shows elastic deformation until the overall strain of the material reaches further at a certain level (Paul and Mukherjee, 2014; Zhuang et al., 2014). Carden et al., 2002 determined the failure mechanisms and ductility of the I-M-DP steel with edge crack under different manufacturing conditions.