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Title: Effect of temperature on the fatigue cracking mechanisms in A356 Al alloy

Abstract

This work builds on our previous investigation of the room temperature fatigue cracking mechanisms of an A356 Al alloy. Here, we analyze the elevated temperature fatigue cracking mechanisms in cast and friction stir processed (FSP) A356, and contrast them with the room temperature behavior. Two sets of FSP parameters were used to modify the microstructure of the cast alloy. After heat treatment, both the FSPed microstructures exhibited severe abnormal grain growth (AGG) leading to a very wide grain size distribution (from a few microns to a few millimeters). During room temperature fatigue tests, the FSP conditions exhibited significant improvements in fatigue lives, even up to an order of magnitude. However, with increasing temperature, the difference in the performance of the FSPed and Cast microstructures decreased until, at 200 °C, all three microstructural conditions exhibited similar fatigue response. Detailed electron back scattered diffraction (EBSD) imaging of failed fatigue specimens was used to study crack behavior. At room temperature, cracks initiated at defect sites or along persistent slip bands (PSBs) and propagated transgranularly. The grain boundaries acted as barriers to crack growth. At elevated temperatures, there was a complete role reversal of the grain boundaries. Cracks initiated along grain boundaries and propagatedmore » intergranularly in all microstructures. Below, we explore this transition of the cracking mechanism in detail.« less

Authors:
 [1];  [2];  [1];  [2];  [3]
  1. University of North Texas
  2. BATTELLE (PACIFIC NW LAB)
  3. general motors Inc.
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1605348
Report Number(s):
PNNL-SA-152052
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Materials Science and Engineering. A. Structural Materials: Properties, Microstructure and Processing
Additional Journal Information:
Journal Volume: 780
Country of Publication:
United States
Language:
English

Citation Formats

Nelaturu, Plalgun, Jana, Saumyadeep, Mishra, Rajiv S., Grant, Glenn J., and Carlson, Blair. Effect of temperature on the fatigue cracking mechanisms in A356 Al alloy. United States: N. p., 2020. Web. doi:10.1016/j.msea.2020.139175.
Nelaturu, Plalgun, Jana, Saumyadeep, Mishra, Rajiv S., Grant, Glenn J., & Carlson, Blair. Effect of temperature on the fatigue cracking mechanisms in A356 Al alloy. United States. doi:10.1016/j.msea.2020.139175.
Nelaturu, Plalgun, Jana, Saumyadeep, Mishra, Rajiv S., Grant, Glenn J., and Carlson, Blair. Tue . "Effect of temperature on the fatigue cracking mechanisms in A356 Al alloy". United States. doi:10.1016/j.msea.2020.139175.
@article{osti_1605348,
title = {Effect of temperature on the fatigue cracking mechanisms in A356 Al alloy},
author = {Nelaturu, Plalgun and Jana, Saumyadeep and Mishra, Rajiv S. and Grant, Glenn J. and Carlson, Blair},
abstractNote = {This work builds on our previous investigation of the room temperature fatigue cracking mechanisms of an A356 Al alloy. Here, we analyze the elevated temperature fatigue cracking mechanisms in cast and friction stir processed (FSP) A356, and contrast them with the room temperature behavior. Two sets of FSP parameters were used to modify the microstructure of the cast alloy. After heat treatment, both the FSPed microstructures exhibited severe abnormal grain growth (AGG) leading to a very wide grain size distribution (from a few microns to a few millimeters). During room temperature fatigue tests, the FSP conditions exhibited significant improvements in fatigue lives, even up to an order of magnitude. However, with increasing temperature, the difference in the performance of the FSPed and Cast microstructures decreased until, at 200 °C, all three microstructural conditions exhibited similar fatigue response. Detailed electron back scattered diffraction (EBSD) imaging of failed fatigue specimens was used to study crack behavior. At room temperature, cracks initiated at defect sites or along persistent slip bands (PSBs) and propagated transgranularly. The grain boundaries acted as barriers to crack growth. At elevated temperatures, there was a complete role reversal of the grain boundaries. Cracks initiated along grain boundaries and propagated intergranularly in all microstructures. Below, we explore this transition of the cracking mechanism in detail.},
doi = {10.1016/j.msea.2020.139175},
journal = {Materials Science and Engineering. A. Structural Materials: Properties, Microstructure and Processing},
number = ,
volume = 780,
place = {United States},
year = {2020},
month = {4}
}