Quantification Study on Dendrite Fragmentation in Solidification Process of Alluminum Alloys

Alloy solidification is an important process to control the mechanical properties of engineering products. During solidification, dendrite fragmentation occurs commonly as a key phenomenon to determine the microstructure and to obtain fine grain size. Recently, in situ synchrotron X-radiography technique was developed and applied to observe thermodynamic behaviors such as dendrite growth and fragmentation during solidification. External forces such as mechanical and electromagnetic stirring, and thermal shock were added into the solidification process to investigate their effects on the fragmentation behavior. However, most work conducted in literature focused on qualitative aspects e.g. morphology transition or solute distribution and quantitative investigation such as determining the specific relationship between fragmentation and solidification conditions was rather limited. In this work, the third generation synchrotron X-radiography technique was used to observe the solidification process of an Al-15%Cu (mass fraction) alloy. Experimental conditions including the strength of the pulsed electromagnetic fields, dendrite growth direction and the temperature gradients were varied and the subsequent effect on fragmentation was studied and quantified. A computer program was developed based on Matlab to perform the image processing and measurement. The fragmentation number according to experiments was counted and correlated to the *国家自然科学基金项目51275269和51205229资助 收到初稿日期: 2014-09-10,收到修改稿日期: 2015-03-25 作者简介:毕成,男, 1988年生,博士生 DOI: 10.11900/0412.1961.2014.00501 第677-684页 pp.677-684