FAST PRECIPITATION PATTERN-FORMATION IN A METALLIC 2-COMPONENT DISSOLUTION-REACTION PROCESS

We here report the observation of precipitation patterns obtained when solid zirconium is allowed to react for few seconds with molten alumi num in the temperature range 720 < T < 850 degrees C. The patterns are made by precipitates of the intermetallic compound Al3Zr in the Al ma trix. Generally, these precipitates show interconnected wavelike struc tures, but in a narrower temperature range (780 < T < 820 degrees C), part of these structures further organize into periodic bands. The pat tern formation in the Al-Zr system is characterized by the strictly bi nary nature of the system, the short time scale for the pattern format ion, and the presence, in the same sample, of different degrees of per iodic organization.