The Strain Partition Behavior and Critical Precipitation Condition of Al3ti (L12 ) Nanoparticle in Al-Cu Alloy

Abstract

Al3Ti precipitate as an ideal strengthening phase receives less attention due to the low solubility of Ti in cast aluminum alloys. In this work, the strain partition behavior and critical precipitation condition of the L12 -type Al3Ti precipitate induced by high Ti content in cast Al-Cu alloy was investigated. Results show that with the addition of 0.4 at.% Ti ( over peritectic point composition ), the primary Al3Ti phase was formed during solidification, and redissolved into the matrix after solution treatment compared with the base alloy with low Ti content. After aging treatment, the Al3Ti (L12 ) precipitates were observed in the alloy with high Ti content. The presence of Al3Ti nano-precipitate allows the aged alloy exhibits superior yield and tensile strengths, which are respectively 9.8% and 16.5% higher than those of the base alloy. The analysis of the atomic displacement field at the precipitation interface revealed that there is a remarkably inhomogeneous strain field at the Al3Ti/α-Al interface, which can strongly inhibit initiation and propagation of crack and thus strengthens the alloy. According to the classical nucleation theory, the critical Ti concentration for Al3Ti (L12 ) precipitate nucleation at 300℃ is 0.37at.%. Because of the redissolution of primary Al3Ti phases, the concentration of Ti atoms in the matrix is sufficient to provide the chemical driving force for the nucleation of the Al3Ti (L12 ) precipitate.

Keywords: Al-Cu alloy, Al3Ti precipitate, strain partition behavior, supersaturation