Fatigue performance improvement in AISI 4140 steel by dynamic strain aging and dynamic precipitation during warm laser shock peening

Warm laser shock peening (WLSP) integrates the advantages of laser shock peening and thermal-mechanical treatment (TMT) to improve material fatigue performance. Compared to traditional laser shock peening (LSP), warm laser shock peening, i.e. LSP at elevated temperature, leads to better performance in many aspects. WLSP can induce nanoscale precipitations by dynamic precipitation and high density dislocation by dynamic strain aging (DSA), resulting in higher surface strength, which is beneficial for fatigue life improvement. Due to pinning of dislocation structure by nanoscale precipitates, and the pinning of dislocation structure by Cottrell atmosphere, or the DSA effect, stability of the dislocation arrangement is significantly increased and the residual stress stability improved. In this study, AISI 4140 steel is used to evaluate WLSP process. It is concluded that the higher residual stress stability and higher surface strength caused by dynamic precipitation and DSA in WLSP leads to fatigue life improvement.

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Improvement in Fatigue Performance of Aluminium Alloy Welded Joints by Laser Shock Peening in a Dynamic Strain Aging Temperature Regime

Materials ◽

10.3390/ma9100799 ◽

2016 ◽

Vol 9 (10) ◽

pp. 799 ◽

Cited By ~ 8

Author(s):

Chun Su ◽

Jianzhong Zhou ◽

Xiankai Meng ◽

Shu Huang

Keyword(s):

Aluminium Alloy ◽

Dynamic Strain Aging ◽

Temperature Regime ◽

Welded Joints ◽

Aging Temperature ◽

Strain Aging ◽

Laser Shock Peening ◽

Dynamic Strain ◽

Laser Shock ◽

Shock Peening

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Alternative Mechanical Surface Treatments for Fatigue Strength Enhancement

Materials Science Forum ◽

10.4028/www.scientific.net/msf.490-491.328 ◽

2005 ◽

Vol 490-491 ◽

pp. 328-333 ◽

Cited By ~ 5

Author(s):

I. Altenberger

Keyword(s):

Residual Stress ◽

High Temperature ◽

Strain Aging ◽

Fatigue Behavior ◽

Laser Shock Peening ◽

Dynamic Strain ◽

Laser Shock ◽

Deep Rolling ◽

Shock Peening ◽

Mechanical Surface

In this paper, The effects of laser-shock peening and high temperature deep rolling on nearsurface microstructures, residual stress states and fatigue behavior of various metallic materials are investigated and discussed. Similar to warm peening (shot peening at elevated temperatures), high temperature deep rolling may induce several favourable effects, especially in ferritic steels, where dynamic strain aging by carbon atoms can be exploited as a major strengthening mechanism. But also in materials without ‚classical‘ strain aging high temperature deep rolling is effective in improving the fatigue behaviour by inducing favourable, e.g. precipitation-hardened, nearsurface microstructures. As a consequence, these modified near-surface microstructures directly alter the thermal and mechanical relaxation behaviour of residual stresses. Laser-shock peening is already used in the aircraft industry (as a mechanical surface treatment for fan-blades) and owes its benefial effects to deep layers of compressive residual stress and work hardening and a relatively smooth surface roughness. Characteristic examples of microstructures and residual stress profiles as generated by laser-shock peening are presented. Moreover, the impact on the fatigue behavior of steels and a titanium alloy is outlined and discussed.

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Observations on Dynamic Strain Aging Manifestation in Inconel 718 Superalloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.930.390 ◽

2018 ◽

Vol 930 ◽

pp. 390-394 ◽

Cited By ~ 1

Author(s):

Monica Costa Rezende ◽

Leonardo Sales Araújo ◽

Sinara Borborema Gabriel ◽

Jean Dille ◽

Luiz Henrique de Almeida

Keyword(s):

Dynamic Strain Aging ◽

Inconel 718 ◽

Strain Aging ◽

Aging Treatment ◽

Tensile Tests ◽

Dynamic Strain ◽

Dynamic Precipitation ◽

Intergranular Cracking ◽

Thermally Activated ◽

Inconel 718 Superalloy

The manifestation of dynamic strain aging (DSA) in Inconel 718 is reported in this work. Analysis were performed in the material with different microstructures resulting from solution anneal and aging treatment. Tensile tests were made under secondary vacuum with temperature ranging between 200 and 950°C and strain rates of 3.2 x 10-3 to 3.2 x 10-5 s-1. Results showed the range of DSA occurrence. Analysis indicates that at lower temperatures, from approximately 200 to 450°C, serrations are controlled by the diffusion of carbon. At higher temperatures, until 800°C, DSA coincided with the occurrence of other thermally activated phenomena: dynamic precipitation, especially γ’’, and Oxidation Assisted Intergranular Cracking (OAIC). It was observed that competitive phenomena affect DSA manifestation directly due to the availability of niobium in solid solution.

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