Abnormal Grain Growth Suppression in AL Alloys

a technology of abnormal grains and al alloys, applied in the field of abnormal grain growth suppression in al alloys, can solve the problems of abnormal grains that can be detrimental to such notch-sensitive mechanical properties, reduce welding strength, fracture toughness, etc., and achieve good strength and ductility

Inactive Publication Date: 2015-11-19
UNITED STATES OF AMERICA AS REPRESENTED BY THE ADMINISTRATOR NAT AERONAUTICS & SPACE ADMINISTRATION
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This process achieves a greater than 90% reduction in abnormal grain growth, improving the strength and ductility of welded aluminum alloys by suppressing abnormal grain growth and stabilizing the microstructure, thereby enhancing the structural integrity of weldments.

Problems solved by technology

The weldment had reduced strength, fracture toughness, and / or ductility due to undesirably large grains.
Abnormal grains can be detrimental to such notch-sensitive mechanical properties.

Method used

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  • Abnormal Grain Growth Suppression in AL Alloys
  • Abnormal Grain Growth Suppression in AL Alloys
  • Abnormal Grain Growth Suppression in AL Alloys

Examples

Experimental program
Comparison scheme
Effect test

example

[0028]This example further demonstrates the effectiveness of using IAT to suppress AGG.

[0029]Investigation of the (sub)grain structure was performed using standard Optical Metallography (“OM”), and Electron Back-Scattered Diffraction (“EBSD”) analytical techniques. Metallurgical analyses were conducted on the same samples for each of the analytical techniques. Traverses between the Advancing / Root and Retreating / Crown intersections were employed, i.e. ‘AR to RC’ traverses. The OM data was collected using two standard specimen preparation / imaging mode combinations; Keller's chemical etching / bright field (K / BF) images and Barker's electro-chemical etching / cross-polarized (B / XP) images. The smaller areas for each EBSD data set contained within were 250 μm×500 μm and comprised of 900-1400 (sub)grains, depending on dimensions. The Mean Linear Intercept (“MU”) methodology used was in conformance with ASTM E112 procedures for the OM data and ASTM E2627 for the EBSD data. Boundaries with mis...

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Abstract

The present invention provides a process for suppressing abnormal grain growth in friction stir welded aluminum alloys by inserting an intermediate annealing treatment (“IAT”) after the welding step on the article. The IAT may be followed by a solution heat treatment (SHT) on the article under effectively high solution heat treatment conditions. In at least some embodiments, a deformation step is conducted on the article under effective spin-forming deformation conditions or under effective superplastic deformation conditions. The invention further provides a welded article having suppressed abnormal grain growth, prepared by the process above. Preferably the article is characterized with greater than about 90% reduction in area fraction abnormal grain growth in any friction-stir-welded nugget.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This patent application is a divisional of U.S. patent application Ser. No. 13 / 272,027 filed Oct. 12, 2011 which claims the benefit of priority to U.S. Provisional Patent Application Nos. 61 / 392,584, filed Oct. 13, 2010; 61 / 445,741, filed Feb. 23, 2011; and 61 / 447,162, filed Feb. 28, 2011. The contents of the foregoing applications are hereby incorporated by reference in their entireties.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT[0002]This invention was made in part with Government support under Contract / Grant Number NNL07AA00B awarded by the National Aeronautics and Space Administration. The Government may have certain rights in this invention.BACKGROUND OF THE INVENTION[0003]Friction stir welding (FSW) is a relatively new welding technique and has been used mainly for aluminum alloys in the transportation industry, in applications such as automobiles, railway vehicles, ships, and rockets. Effective friction stir we...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): C22F1/05B23K20/12B23K20/26C22C21/08
CPCC22F1/05C22C21/08Y10T403/478B23K20/129B23K20/26B23K20/122C22C21/10C22C21/12C22F1/04C21D9/50B23K20/2336B23K2103/10
InventorHALES, STEPHEN J.CLAYTOR, HAROLD D.ALEXA, JOEL A.
OwnerUNITED STATES OF AMERICA AS REPRESENTED BY THE ADMINISTRATOR NAT AERONAUTICS & SPACE ADMINISTRATION