Prediction and Experimental of Yield Strengths of As-Quenched 7050 Aluminum Alloy Thick Plates after Continuous Quench Cooling

Shengping Ye,Kanghua Chen,Changjun Zhu,Li Liu,Songyi Chen

doi:10.3390/met10010026

Abstract

The aim of this study was to predict the yield strength of as-quenched aluminum alloys according to their continuous quench cooling path. Our model was established within the framework of quench factor analysis (QFA) by representing a quenching curve as a series of consecutive isothermal transformation events and adding the yield strength increments after each isothermal step to predict the yield strength after continuous quench cooling. For simplification; it was considered that the effective hardeners during quenching were the nanosized solute clusters formed at low temperatures, whereas the other coarse precipitates were neglected. In addition, quenching tests were conducted on aluminum plates with different thicknesses. The predictions were compared with the experimental measurements, and the results showed that the predictions fit the measurements well for the 40- and 80-mm-thick plates but overestimated the as-quenched yield strength at the mid-thickness of the 115-mm-thick plates.

Highlights

Heat-treatable aluminum alloys are known to achieve high performance through the development of a precipitation-hardened microstructure produced by aging a quenched supersaturated solid solution [1,2]
In addition to the coarse precipitates, nanosized precipitates, i.e., solute clusters, will form during quenching, and these nanosized precipitates may harden the material to some extent, producing a quench-induced hardening effect, which enables larger residual stress magnitudes to be supported [7]
The yield strength model of the as-quenched 7050 aluminum alloy is established within the framework of quench factor analysis (QFA)

Summary

Introduction

Heat-treatable aluminum alloys are known to achieve high performance through the development of a precipitation-hardened microstructure produced by aging a quenched supersaturated solid solution [1,2]. The quench cooling rate should be maximized to prevent quench-induced coarse precipitation with sizes of approximately 100 nm. These precipitates are undesirable, since they reduce the available solute for the aging process and do not substantially harden the material [3]. In addition to the coarse precipitates, nanosized precipitates, i.e., solute clusters, will form during quenching, and these nanosized precipitates may harden the material to some extent, producing a quench-induced hardening effect, which enables larger residual stress magnitudes to be supported [7]. In the case of thick plates, a thermomechanical model that does not account for the quench-induced hardening effect underestimates the residual stress. The quench-induced hardening effect will be discussed in this study

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