单室Gasar工艺中抽拉速率对藕状多孔Cu气孔形貌的影响

EFFECT OF WITHDRAWING RATE ON PORE MORPHOLOGY OF LOTUS-TYPE POROUS COPPER PRODUCED BY SINGLE-MOLD GASAR TECHNIQUE

采用单室Gasar工艺,通过实验研究和Procast凝固模拟相结合,研究了坩埚抽拉速率对凝固界面形貌、铸锭平均凝固速率、藕状多孔Cu气孔形貌、气孔生长方向以及相应多孔结构参数的影响规律.研究表明,随着抽拉速率的升高,凝固界面从凸界面向平界面再向凹界面演化.当凝固界面为凸界面和凹界面时,气孔生长方向都会偏离铸锭抽拉方向.而只有在合适的抽拉速率条件下使凝固界面以平界面方式推进,才能获得气孔完全平直生长的优质藕状多孔Cu.实验和模拟结果显示,在本实验条件下,当抽拉速率为1 mm/s时,铸锭凝固界面基本以平界面方式推进;藕状多孔Cu铸锭的气孔率不受抽拉速率的影响,但随着抽拉速率的增大,平均孔径和通孔率会逐渐降低.

A single mold Gasar process was developed to fabricate lotus-type porous copper with long and straight pores. The effects of withdrawing rate on the solidification front shape, pore morphology and average solid- ification rate of porous copper ingots were investigated through experimental study and Procast simulation. The re- suits show that the solidification front shape evolves from convex to planar, then to concave with increasing with- drawing rate. In this work, 1.0 mm/s is an appropriate rate for planar solidification front. In this case, all of the gas pores grow along the axial direction （parallel to the withdrawing direction） and the pores＇ straightness is the best. The average porosities of copper ingots are constant and independent of the withdrawing rate. But the average porediameter and penetration ratio of gas pores decreased with increasing withdrawing rate.