The distribution and flow of nickel powder and carbon nanotubes mixed in an aluminum material via friction stir welding
The aviation industry is interested in advance technology that includes composites and friction stir welding. As there are many advantages to friction stir welding (FSW), there are always ways to improve a new process such as friction stir processing/welding. One such improvement is to produce a metal matrix/carbon nanotube (CNT) composite via FSW. It is theorized in this work that a weld can be tailored to desired mechanical and physical properties. The background for such research is needed, and that is the purpose of this thesis. Nickel and CNTs FSW composite material was produced by welding over a powder filled groove on the surface of 2024-T3 plate. Mechanically compacting the powder was found to result in no noticeable loss of powder. Further, the nickel powder welded with the parameters used in this experiment was found to create a well distributed composite when the groove was 0.05” deep. When the groove was deeper then the nickel particles tended to stay agglomerated just below the surface in a line. The line of nickel particles started from the advancing side and as the groove was made deeper the particles in a line move toward the retreating side. FSW/CNTs composite material was different with different depths of grooves. For a 0.05” depth grove the CNTs were seen to form lines in the metallography going down from the top advancing side to the upper mid-section of the advancing side of the weld. With deeper groves the CNTs would stay agglomerated starting from the original position just below 0.05” deep groove and at greater depths the CNTs would move up in circular motion until the CNTs reach the surface of the weld. The strength of a FSW/CNT composite under the welding parameters used was found to produce a weaker weld than the base aluminum weld. Cracks were seen to form along the CNTs lines going from the top advancing side to the upper middle advancing side. The tool used in this study was a high welding speed tool. Finally the flow of nickel and carbon nanotubes was analyzed, and the distribution of the particles after welding was characterized and summarized. To successfully produce FSW/CNT composite material, it is recommended that a tool designed for slow, high temperature friction stir processing, one that maximizes maelstrom flow, be tested in future work.
Wichita State University, College of Engineering, Dept. of Mechanical Engineering
Includes bibliographic references (leaves 117-121)