MS界面稳定性判据新探

NEW RESEARCH OF MS INTERFACE STABILITY CRITERION

给出了定向凝固平界面稳定性新的判据，（ｌ＋３ｋ／ｙ０）ξ ＋［１＋（１＋ ｋ）ｙ０／４ｋ］≥１其中Ａ为无量纲速度，ξ≡ＧＬＳ／ｍＧｃ，ｙ０是有关Ａ和ξ的一个二次方程的根．新判据的最大特点是可直接由凝固参数推断界面的稳定性，不用解高次方程．发现ＭＳ绝对稳定性速度Ｖａ仅在加权温度梯度ＧＬＳ→０时才是界面稳定性的临界速度．当 ＧＬＳ＞０时，Ｖａ大于实际的临界速度．给出了一个新的绝对稳定性梯度条件，并求出了最小的绝对稳定性无量纲临界梯度．

A a new stability criterion has been put up based on the planar interface stability under directional solidification by analyzing MS theory,(1 + 3k/y0)ξ + [1 +(1 + k)y0/4k] ≥1 there A is dimensionless velocity, ξ= GLS/mGc and y0 is a root of a square equation about A and ξ. The new criterion succeeds in avoiding solution of high grade equation when applied, so that it can be conveniently used to predicate interface stability. A new temperature gradient criterion is also deduced and the minimum dimensionless temperature gradient of absolute stability is proved to be 1/16. It has been indicated that the MS absolute stability velocity Va is the interface stability critical velocity when generalized temperature gradient GLS→0, while the critical velocity may be less than Va when GLS>0.