New in-situ Al matrix composites based on Al-Ni-La eutectic

Abstract

The phase equilibria in the Al-Ni-La system and the microstructure and mechanical properties of the alloys with varying La and Ni contents were investigated by using thermodynamic calculations (Thermo-Calc software), electron microscopy, energy dispersive spectrometer and tensile test. It is shown that the microstructure of the most promising alloys with La contents of up to 8 wt% and Ni contents of up to 5 wt% consists of Al primary crystals and ultrafine ternary eutectic (particle thickness is about 30–70 nm) which in turn consist of binary Al3Ni and Al4La compounds. However, at an excessive concentration of La and Ni, the formation of the previously undescribed Al9LaNi2 ternary compound is observed. The actual structure of the ternary diagram is proposed based on experimental data. Uniaxial tensile testing of the promising Al7La4Ni alloy in as-cast state revealed an ultimate tensile strength of about 250 ± 10 MPa, a yield strength of 200 ± 10 MPa and a ductility of 3.0 ± 0.2%.