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Metals 2017, 7(9), 370; doi:10.3390/met7090370

Effects of Post-Sinter Processing on an Al–Zn–Mg–Cu Powder Metallurgy Alloy

1
Department of Mechanical Engineering, Dalhousie University, Halifax, NS B3H 4R2, Canada
2
Advanced Engineering, GKN Sinter Metals LLC, Auburn Hills, MI 48326, USA
*
Author to whom correspondence should be addressed.
Received: 16 August 2017 / Revised: 7 September 2017 / Accepted: 8 September 2017 / Published: 13 September 2017
(This article belongs to the Special Issue Advanced Mechanical Testing of Powder Metallurgy Alloys)
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Abstract

The objective of this work was to study the effects of several post-sinter processing operations (heat-treatment, sizing, shot peening) on a press-and-sinter 7xxx series aluminum powder metallurgy (PM) alloy. The characterization of the products was completed through a combination of non-contact surface profiling, hardness measurements, differential scanning calorimetry (DSC), transmission electron microscopy (TEM), X-ray diffraction (XRD), tensile, and three-point bend fatigue testing. It was determined that sizing in the as-quenched state imparted appreciable reductions in surface hardness (78 HRB) and fatigue strength (168 MPa) relative to counterpart specimens that were sized prior to solutionizing (85 HRB and 228 MPa). These declines in performance were ascribed to the annihilation of quenched in vacancies that subsequently altered the nature of precipitates within the finished product. The system responded well to shot peening, as this process increased fatigue strength to 294 MPa. However, thermal exposure at 353 K (80 °C) and 433 K (160 °C) then reduced fatigue performance to 260 MPa and 173 MPa, respectively, as a result of residual stress relaxation and in-situ over-aging. View Full-Text
Keywords: aluminum alloys; powder metallurgy; X-ray diffraction; fatigue; age hardening; residual stress; electron microscopy; thermomechanical processing; precipitation hardening aluminum alloys; powder metallurgy; X-ray diffraction; fatigue; age hardening; residual stress; electron microscopy; thermomechanical processing; precipitation hardening
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Harding, M.D.; Donaldson, I.W.; Hexemer Junior, R.L.; Bishop, D.P. Effects of Post-Sinter Processing on an Al–Zn–Mg–Cu Powder Metallurgy Alloy. Metals 2017, 7, 370.

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