In-situ formation of Al3Ni nano particles in synthesis of Al 7075 alloy by friction stir processing with Ni powder addition?

Bulk aluminum 7075 alloy strengthened by nano-sized Al-Ni intermetallic particles is synthesized by friction stir processing (FSP). Al 7075 alloy powders mixed with 10 wt% Ni nano powders were used as feedstock. The extensive thermal-mechanical actions by FSP accelerate the reaction and inter-diffusion between Al 7075 powder particles and Ni nano powder particles, resulting in the formation of Al3Ni nano particles, in-situ during FSP, confirmed by scanning electron microscopy and X-ray diffraction. The presence of the Al3Ni nano particles in the Al 7075 matrix increases the micro hardness by 19.0 % and 14.6 %, respectively, under as-processed and T6 aged conditions, compared to the one synthesized by FSP from 100 % 7075 alloy powder. The hardness increment agrees with the estimation from the Orowan strengthening effect of the Al3Ni reinforcement. Furthermore, Al 7075 alloy with in-situ formed Al3Ni shows a tendency of promoting T-Al2Mg3Zn3 and inhibiting eta-MgZn2 precipitation during post synthesis heat treatment between 50 and 500 degrees C. This work suggests the potential of FSP as an effective process to bulk synthesize Al alloys with in-situ formation of Al3Ni nano particles to further enhance the properties.

Automated summary

In this study, bulk aluminum 7075 alloy strengthened by nano-sized Al-Ni intermetallic particles was successfully synthesized through friction stir processing (FSP). The FSP method promotes the formation of Al3Ni nano particles in-situ through the reaction and inter-diffusion between the aluminum and nickel powders. The presence of these particles significantly increases the micro hardness and modifies the precipitation behavior of the alloy during heat treatment.