Effect of Microstructure Changes on Mechanical Properties of La₆₆Al₁₄(Cu, Ni)₂₀ Amorphous and Crystalline Alloys

Abstract

The microstructure, and phase selections of La₆₆Al₁₄(Cu, Ni)₂₀ alloy were studied by Bridgman solidifications, and composite materials of dendrites in amorphous matrix or micro- and nano- sized eutectic matrix were formed with different cooling rates. The volume fraction of the dendrite phase reaches a maximum at the cooling rate of about 15 K/s, the secondary dendrite arm spacing λ₂ decreases from 4.3 µm to 0.6 µm with the increasing of cooling rate R, and obeys the equation of λ₂R⁰.⁵&#x2077=1.74µm(K/s)R⁰.⁵&#x2077. The compression strength, as well as the elastic strain limit of the dendrite/amorphous matrix composite are 600 MPa, and 2.3%, respectively. Improved ductility was observed for the dendrite amorphous matrix composites with more dendrite phase by slow cooling rate.