Hard-alpha particle behavior in a titanium alloy liquid pool

The Canadian and French university teams have joined their efforts in carrying out an experimental and theoretical study of the dissolution behavior of the hard-alpha defect. Synthetic hard-alpha particles of up to 6 weight percent of nitrogen were prepared by tungsten-arc melting titanium in a nitrogen atmosphere. The nitrided samples were immersed in established liquid pools of titanium alloys which are performed in a water crucible using arc heating. From the metallographic examinations and microprobe analysis the mechanism of dissolution is discussed. Moreover, a numerical representation of the dissolution problem was developed including the two physical phenomena that govern the dissolution: - the transient diffusion of nitrogen with intermediate solid phases. - the transport of nitrogen in the mushy zone or the liquid metal surrounding the particle. Simulation results are given for different operating conditions.