Investigation of micro-structure and mechanical properties of three steel alloys

Abstract

The significant demands of steel in industrial applications and automotive and building industries are increasing. Thus, there is a need for the improvement of its mechanical properties by adding suitable alloy elements to them so that they have more strengthweight ratio. The objective of this research is to study the effect of adding various alloys to steel material and ther effects on tensile and impact strengths, hardness, and  microstructure. The tensile test was conducted on a round bar standard specimens of three kinds of steel having different compositions to investigate their mechanical properties. The results of tensile tests are given in tables, based on their stress-strain curves plotted to facilitate the design engineer to know the strength and accordingly design lightweight structures from this material. After the test, the microstructure of the fracture surface was observed using an inverted microscope. The tensile and impact strengths and hardness of carbon steel, EN 8 steel, and mild steel were evaluated and compared based on the chemical composition and microstructural observation. The experimental result showed that the increasing percentage of carbon and silicon in EN 8 steel increased its ultimate tensile and yielded strengths but reduced the percentage elongation compared to carbon steel. Similarly, less content of manganese with an increased content of nickel enhanced the impact strength of the mild steel but slightly reduced the tensile strength and hardness of mild steel compared to EN 8 steel.