Tensile and plane bending fatigue properties of pure iron and iron-phosphorus alloys at room temperature in the air

摘要

In many low alloys as well as in plain carbon steels, segregation of trace element, especially phosphorus (P), sulfur (S), arsenic (As), etc. is really a great problem. Because, it induces brittleness in the steels and subsequently causes deterioration in mechanical properties. In this present work, commercial grade of pure iron with varying amount of phosphorus contents such as 0.001, 0.11 and 0.21 wt% were annealed at different temperatures and time periods to induce varying degrees of temper embrittlement. After annealing heat treatment, tensile and plane bending fatigue tests of these ferrous alloys were carried out at room temperature in the air. The tensile and fatigue fracture surfaces were observed under scanning electron microscope (SEM) to study various fracture features. It has been found that the addition of phosphorus in the pure iron increased the tensile strength, however, it decreased the ductility. The grain refining effects and increase in tensile strength due to additions of P were found to be very significant. However, with increase in annealing time at any temperature, the mechanical properties were found to deteriorate gradually and the fatigue fracture mode was also found to change from its transgranular cleavage type to intergranular type fracture.