先进材料疑固实验室 Constrained growth Laboratory of Advanced Materials Solidification The general condition for growth: For directional solidification in situation 3,the condition can be expressed as: - LCo(1-k) R kDL of Advanced Materials Solic 上降充通大学 SHANGHAI JIAO TONG UNIVERSITY
Constrained growth The general condition for growth: For directional solidification in situation 3, the condition can be expressed as:
先进材料疑固实验室 Constrained growth Laboratory of Advanced Materials Solidification The initiation of dendritic growth: Breakdown of unstable planar S/L interface perturbations. The tips of perturbations grow faster than their depressions due to constitutional undercooling the perturbations change from sinusoidal to cellular. The cell growth direction deviates towards the preferred crystallographic direction. For metals with a cubic crystal structure,this direction is <100>. nced 上游充〔大￥ SHANGHAI JIAO TONG UNIVERSITY
Constrained growth The initiation of dendritic growth: Breakdown of unstable planar S/L interface perturbations. The tips of perturbations grow faster than their depressions due to constitutional undercooling the perturbations change from sinusoidal to cellular. The cell growth direction deviates towards the preferred crystallographic direction. For metals with a cubic crystal structure, this direction is <100>
先进材料疑固实验室 Constrained growth Laboratory of Advanced Materials Solidification Planar structure dTL(x)/dxl When a single phase alloy G T satisfies: T(⑧ G>- mCo(1-k R Dk there is no contitutional undercooling in front of the interface.The crystal grows Local unstable interface as plane interface.Apart from the initial stage and last stage with the temperature stable interface and constitution variation,the process is similar as pure metal planar growth. 上浒充通大学 SHANGHAI JIAO TONG UNIVERSITY
Planar structure When a single phase alloy satisfies: there is no contitutional undercooling in front of the interface. The crystal grows as plane interface. Apart from the initial stage and last stage with the temperature and constitution variation, the process is similar as pure metal planar growth. Constrained growth D k m C (1 k ) R G L L L 0 Local unstable interface stable interface