High strength weld metal design through nanoscale copper precipitation

Abstract

Deployment of advanced steels with superior yield and tensile strengths, as well as, toughness, ballistic and shock resistance is challenged by the lack of matching filler metals that can yield similar mechanical properties. In this research, strengthening of the weld metal through rapid formation of nanoscale copper precipitates, during reheating, within a ferrite matrix was proposed. A weld metal containing a nominal concentration of 2.49wt.% Cu, without any precipitation reaction, was soft 300HVN. On precipitation of nanoscale copper precipitates, with an average radius of 2.2±0.45nm and a high number density of 2.9×1023m−3, the hardness increased by 50–100HVN. The magnitude of this increase was inversely related to the peak temperature. The precipitation and extent of strengthening was rationalized based on thermodynamic calculations and Russell–Brown model, respectively.