Influence of Phosphorus Grain Boundary Segregation on Fracture Behaviour of Iron-Base Alloys

Abstract

Chemical and structural changes at the grain boundaries were investigated to quantify their influence on fracture behaviour of austenitic stainless steels and model ferritic Fe-Si-P alloys. The balance between the size and the area density of intergranular particles was found to be one of the most decisive factors influencing sensitivity of the steels to intergranular fracture. The precise dependence of the energy of intergranular fracture on the phosphorus grain boundary concentration was also determined.

Geometrical Shielding Produced by Intergranular Crack-Tip Branching in Fe–V–P Alloy

“…( 3). In our previous studies on phosphorus segregation in Fe-Si-P and Fe-V-P alloys [7,[13][14][15][16][17], the roomtemperature value of K Ici at P-segregated GBs was found to be very low and comparable with the fracture resistance of cleavage facets at very low temperatures. However, the secondary cracks identifying the splitting of the main crack front preferentially at triple junctions can also be observed.…”

“…This kind of shielding belongs to so called extrinsic components of fracture toughness which can be used as a toughening mechanism in the research and technology of advanced ceramics [11]. However, GIS constitutes a very important component also in the case of mixed ductile/intercrystalline or cleavage/intercrystalline fracture observed in metals [7,[12][13][14][15]. Thus, the extrinsic component K Ice may be very high when the intergranular fracture cannot be avoided (strong corrosion or hydrogen assistance, GB segregation of impurities and tempering embrittlement of high-strength steels).…”