High cycle fatigue resistance of AISI E9310 carburized steel with two different levels of surface retained austenite and surface residual stress

This study investigates the very-high-cycle fatigue (VHCF) behavior at elevated temperature (650 °C) of the Inconel 718 alloy fabricated by selective laser melting (SLM). The results are compared with those of the wrought alloy. Large columnar grain with a cellular structure in the grain interior and Laves/δ phases precipitated along the grain boundaries were exhibited in the SLM alloy, while fine equiaxed grains were present in the wrought alloy. The elevated temperature had a minor effect on the fatigue resistance in the regime below 108 cycles for the SLM alloy but significantly reduced the fatigue strength in the VHCF regime above 108 cycles. Both the SLM and wrought specimens exhibited similar fatigue resistance in the fatigue life regime of fewer than 107–108 cycles at elevated temperature, and the surface initiation mechanism was dominant in both alloys. In a VHCF regime above 107–108 cycles at elevated temperature, the wrought material exhibited slightly better fatigue resistance than the SLM alloy. All fatigue cracks are initiated from the internal defects or the microstructure discontinuities. The precipitation of Laves and δ phases is examined after fatigue tests at high temperatures, and the effect of microstructure on the formation and the propagation of the microstructural small cracks is also discussed.

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Heat Treatment Effects on Distortion, Residual Stress, and Retained Austenite in Carburized 4320 Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.783-786.692 ◽

2014 ◽

Vol 783-786 ◽

pp. 692-697 ◽

Cited By ~ 2

Author(s):

Andrew Clark ◽

Randy J. Bowers ◽

Derek O. Northwood

Keyword(s):

Heat Treatment ◽

Residual Stress ◽

Retained Austenite ◽

Compressive Residual Stress ◽

Surface Residual Stress ◽

Depth Profiles ◽

Size And Shape ◽

Austenite Content ◽

Treatment Conditions ◽

The Difference

The effects of heat treatment on distortion, residual stress, and retained austenite were compared for case-carburized 4320 steel, in both the austempered and quench-and-tempered condition. Navy C-ring samples were used to quantify both size and shape distortions, as well as residual stress. The austempering heat treatment produced less distortion and a higher surface residual stress. Both hoop and axial stresses were measured; the difference between them was less than seven percent in all cases. Depth profiles were obtained for residual stress and retained austenite from representative C-ring samples for the austempered and quench-and-tempered heat treatment conditions. Austempering maintained a compressive residual stress to greater depths than quench-and-tempering. Quench-and-tempering also resulted in lower retained austenite amounts immediately beneath the surface. However, for both heat treatments, the retained austenite content was approximately one percent at depths greater than 0.5 mm.

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High Cycle Fatigue Resistance and Reliability Assessment of Flexible Printed Circuitry

Journal of Electronic Packaging ◽

10.1115/1.1462628 ◽

2002 ◽

Vol 124 (3) ◽

pp. 254-259 ◽

Cited By ~ 9

Author(s):

Elena Martynenko ◽

Wen Zhou ◽

Alexander Chudnovsky ◽

Ron S. Li ◽

Larry Poglitsch

Keyword(s):

Fatigue Resistance ◽

High Cycle Fatigue ◽

Failure Mechanisms ◽

Three Dimensional ◽

Reliability Assessment ◽

Core Layer ◽

High Strength ◽

Multiple Cracks ◽

Material System ◽

Cycle Fatigue

Flexible printed circuitry (FPC) is a patterned array of conductors supported by a flexible dielectric film made of high strength polymer material such as polyimide. The flexibility of FPC provides an opportunity for three dimensional packaging, easy interconnections and dynamic applications. The polymeric core layer is the primary load bearing structure when the substrate is not supported by a rigid plate. In its composite structure, the conductive layers are more vulnerable to failure due to their lower flexibility compared to the core layer. Fatigue data on FPCs are not commonly available in published literature. Presented in this paper is the fatigue resistance and reliability assessment of polyimide based FPCs. Fatigue resistance of a specific material system was analyzed as a function of temperature and frequency through experiments that utilized a specially designed experimental setup consisting of sine servo controller, electrodynamic shaker, continuity monitor and temperature chamber. The fatigue characteristics of the selected material system are summarized in the form of S-N diagrams. Significant decrease in fatigue lifetime has been observed due to higher displacements in high cycle fatigue. Observed temperature effect was however counter-intuitive. Failure mechanisms are discussed and complete fracture analysis is presented. In various FPC systems, it has been found that the changes take place in FPC failure mechanisms from well-developed and aligned single cracks through the width at low temperature to an array of multiple cracks with random sizes and locations at high temperature.

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