The Role of Ferrotitanium as an Inoculant on the Microstructure and Mechanical Properties of Low-Alloy Steel

In this work, the effects of ferrotitanium (0.5 wt.%) as an inoculant on the microstructure and mechanical properties of 0.24 % carbon-1 % chromium-1 % manganese-0.5 % silicon steel were studied. Optical microscopy and scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) microanalysis were used for microstructural investigations. The phase structure of the ferrotitanium-added alloys was studied using X-ray diffraction (XRD). Microstructural observations show that a fine upper bainite lath is formed and allotriomorphic ferrite is eliminated by adding ferrotitanium to the main alloy. XRD revealed the presence of ferrite and austenite in the microstructure. Also, a decrease in dendrite arm spacing (DAS) was observed for 0.5 wt.% ferrotitanium-added alloy. Addition of 0.5 wt.% ferrotitanium caused the formation of titanium-molybdenum-carbon precipitates in austenite grain boundaries so that these particles acted as nucleon's in austenite grain boundary and refined the microstructure. The yield strength, ultimate tensile strength, and percent elongation to fracture of the ferrotitanium-added samples are increased by 65, 68, and 57 %, respectively. Finally, the fracture surface of the alloys showed a cleavage fracture for the inoculated alloy.