Recent Advances in Friction Stir Welding/Processing of Aluminum Alloys: Microstructural Evolution and Mechanical Properties

ABSTRACT

Friction stir welding (FSW), a highly efficient solid-state joining technique, has been termed as “green” technology due to its energy efficiency and environment friendliness. It is an enabling technology for joining metallic materials, in particular lightweight high-strength aluminum and magnesium alloys which were classified as unweldable by traditional fusion welding. It is thus considered to be the most significant development in the area of material joining over the past two decades. Friction stir processing (FSP) was later developed based on the basic principles of FSW. FSP has been proven to be an effective and versatile metal-working technique for modifying and fabricating metallic materials. FSW/FSP of aluminum alloys has prompted considerable scientific and technological interest since it has a potential for revolutionizing the manufacturing process in the aerospace, defense, marine, automotive, and railway industries. To promote widespread applications of FSW/FSP technology and ensure the structural integrity, safety and durability of the FSW/FSP components, it is essential to optimize the process parameters, and to evaluate thoroughly the microstructural changes and mechanical properties of the welded/processed samples. This review article is thus aimed at summarizing recent advances in the microstructural evolution and mechanical properties of FSW/FSP aluminum alloys. Particular attention is paid to recrystallization mechanism, grain boundary characteristics, phase transformation, texture evolution, characteristic microstructures, and the effect of these factors on the hardness, tensile and fatigue properties as well as superplastic behavior of FSW/FSP aluminum alloys.

KEYWORDS:

• Friction stir welding
• friction stir processing
• aluminum alloys
• microstructure
• mechanical property

Notes

* A search from a few authoritative databases using a key word of “friction stir” on May 7, 2017 showed: 6,113 publications from the Web of Science; 7,699 publications from the Engineering Village (Compendex only); 22,124 publications from ScienceDirect of Elsevier; or about 49,500 publications from Google Scholar so far.

Additional information

Funding

The authors would like to thank the support of the National Natural Science Foundation of China (Grant Nos. 51331008 and 51305304), and Natural Sciences and Engineering Research Council of Canada (NSERC), Premier's Research Excellence Award (PREA), NSERC-DAS award, Canada Foundation for Innovation (CFI), and Ryerson Research Chair (RRC) program.