EFFECT OF PHOSPHORUS ON HOT DUCTILITY OF HIGH-PURITY IRON

Tensile rests on high purity Fe-P alloys with 0, 0.05 and 0.1 mass%P w ere carried out at temperatures between 300 K and 1073 K to clarify th e intrinsic effect of phosphorus on the mechanical properties of iron at elevated temperatures. Microstructures of as-quenched, interrupted and ruptured specimens were observed. Experimental results show that t he addition of phosphorus causes a remarkable increase in proof stress of high purity iron at 300 K, but the increase in proof stress by pho sphorus decreases with increasing test temperature. The strengthening effect of phosphorus reduces to zero at 1073 K. High purity iron and F e-P alloys rupture at almost 100% reduction in area at the whole test temperatures. However, Fe-P alloys show much larger elongation at test temperatures above 773 K than high purity iron. The increased elongat ion of high purity iron by addition of phosphorus was shown to be rela ted to the effect of phosphorus on dynamic recovery and recrystallizat ion of iron as its intrinsic effect.