Precipitation Behavior and Quenching Sensitivity of a Spray Deposited Al-Zn-Mg-Cu-Zr Alloy

Xiaofei Sheng,Mingpu Wang,Qian Lei,Zhu Xiao

doi:10.3390/ma10091100

Abstract

Precipitation behavior and the quenching sensitivity of a spray deposited Al-Zn-Mg-Cu-Zr alloy during isothermal heat treatment have been studied systematically. Results demonstrate that both the hardness and the ultimate tensile strength of the studied alloy decreased with the isothermal treatment time at certain temperatures. More notably, the hardness decreases rapidly after the isothermal heat treatment. During isothermal heat treatment processing, precipitates readily nucleated in the medium-temperature zone (250–400 °C), while the precipitation nucleation was scarce in the low-temperature zone (<250 °C) and in the high-temperature zone (>400 °C). Precipitates with sizes of less than ten nanometers would contribute a significant increase in yield strength, while the ones with a larger size than 300 nm would contribute little strengthening effect. Quenching sensitivity is high in the medium-temperature zone (250–400 °C), and corresponding time-temperature-property (TTP) curves of the studied alloy have been established.

Highlights

In the past decades, 7xxx series (Al-Zn-Mg-Cu) aluminum alloys exhibited an outstanding performance and attracted much interest in many industry fields, especially in the automotive and the aviation field [1,2,3], because of their high strength, high ductility, and low density [4,5]
Before the spray deposition process, blocks of Al, Zn, Mg, Cu, and Al-Zr master alloy were melted, and the molten melt was atomized by N2 gas
A high strength Al-Zn-Mg-Cu-Zr alloy was synthesized by using a spray deposition technology followed by hot extrusion, solution treatment, isothermal heat treatment, and aging treatment

Summary

Introduction

7xxx series (Al-Zn-Mg-Cu) aluminum alloys exhibited an outstanding performance and attracted much interest in many industry fields, especially in the automotive and the aviation field [1,2,3], because of their high strength, high ductility, and low density [4,5]. The high strength makes the products strong, and the high ductility allows the products to be forming during the machining process, and the low density saves the energy cost and reduces the carbon emission. Techniques, such as accumulative roll bonding [11], high-pressure torsion [12], equal channel angular pressing [13], and friction stir processing [14], were proven to be effective methods to refine the structure and enhance the strength. The spray deposition technology has been developed rapidly [23,24]

Methods

Results

Discussion

Conclusion