DOUBLE-STREAM-POURING TECHNIQUE FOR PRODUCTION OF GRADIENT MATERIALS BY CONTINUOUS-CASTING

A novel method for producing gradient materials by continuous casting is introduced. By using many-stream-pouring technique, samples with gr adient distribution of alloy composition along the cross section have been prepared. The main difference of this method from the conventiona l continuous casting is the pouring system equipped with two sets of t undishes for liquid metals of different alloy compositions. Special co nsideration is given to the promotion and control of the cross-section al mass transport. The steady hear transfer and mass flow ensure a par tial mixing of two metals and yield a continously varying composition distribution. By adjusting the processing parameters, composition prof ile with different shapes can be achieved. First experiments have been carried out in Al-Si system and Al-Cu system for three series of Al/A lSi, AlSi/Al and AlCu/Al. It is shown that the alloy composition, the microstructure and the mechanical property change smoothly from the ce ntre to the surface of the samples. This simple and practical method i s potential for mass prodution of ''structural gradient materials'' an d may offer a new way for alloy design.