The morphology evolutions of the sidebranch during the solidification of weld pool under transient conditions are investigated by experiments and a quantitative phase field (PF) method. The equations represent the transient conditions of the weld pool which are presented and coupled to the PF model. The sidebranching spacing obtained by the PF simulation agrees well with that obtained by the experimental result. The sidebranching spacings formed in transient growth of the weld pool are larger than that under the steady-state conditions extracted from the transient conditions at instantaneous time, and the reasons are discussed by conducting noise amplification theory and time-dependent linear stability analyses.

通过实验和定量相场（PF）方法研究了瞬态条件下熔池凝固过程中侧枝的形态演变。这些方程代表了焊接熔池的瞬态条件，并与 PF 模型耦合。PF模拟得到的侧支间距与实验结果非常吻合。熔池瞬态生长形成的侧支间距大于从瞬时瞬态条件中提取的稳态条件下形成的侧支间距，并通过噪声放大理论和瞬态线性稳定性分析讨论了原因。