Hot ductility of an Fe‐10%Ni alloy during penetration of copper

Abstract

Today's available theories for hot crack formation are based on the fact that hot cracks are formed in the presence of liquid films in the interdendritic areas or at the grain boundaries, which are exposed to tensile stress. Copper is well known to cause hot shortness in steels. In order to study how the liquid embrittles the material, high-temperature tensile tests were performed at two strain rates during the penetration of liquid copper into Fe-10%Ni. The penetration distance was measured in samples that were exposed to strain without fracturing. The ductility (area reduction), strain and ultimate tensile stress were determined. Microprobe analysis was performed on the fractured samples. The transition temperature of ductility was found at 1400-1450 • C without copper penetration whereas it occurred at 1025-1078 • C during the pene-tration of copper, i.e. copper starts to embrittle at a temperature below its melting point. The microprobe measurements showed that the diffusion rate of copper into Fe-10%Ni was enhanced when the lattice was strained. The results are discussed in terms of a new theory concerning vacancy formation and condensation as the dominating mechanism for hot crack formation during solidification.

Weldability Evaluation of a Cu-Bearing High-Strength Blast-Resistant Steel

“…This range is compared with the slightly higher ductility transition temperature range of 1673 K to 1723 K (1400°C to 1450°C) for an Fe-10Ni alloy containing only a negligible amount of Cu. [33] From thermodynamic calculations, the maximum solubility of Cu in austenite is predicted to be 13.9 wt pct with a nominal 6.5 wt pct Ni alloying addition (Figure 9). Beyond the point of maximum Cu solubility in austenite for the Fe-Cu-6.5Ni system, a sharp decrease in solubility is then observed up to the predicted liquidus temperature.…”

Hot Ductility Loss in a Fe-Ni-Based Superalloy

“…However, A-286 has been found to be prone to intergranular fracture when it is deformed at high temperatures [4,5]. The issue of hot ductility loss has attracted much attention in the superalloy industry, and numerous studies have been reported [6][7][8][9][10][11]. Most of these studies have suggested impurities segregations and formation of precipitates along grain boundaries to be OPEN ACCESS responsible for loss of ductility.…”