Surface nanocomposite fabrication on AA6063 aluminium alloy using friction stir processing: an investigation into the effect of the tool-shoulder diameter on the composite microstructure

Abstract

In this work, surface metal matrix composites (SMMCs) were fabricated on AA6063 base metal through friction stir processing (FSP). In all the samples for surface composites, grooves of 2 mm × 2 mm were made along the centreline of plates and TiB2 powder (~80 nm) was filled and compacted in these grooves. A pinless tool was employed to initially cover and compact the grooves filled with TiB2 particles to prevent it from sputtering during FSP. Tools of different shoulder diameters (16, 18, and 20) mm with anti-clockwise scrolls on the shoulder surface were used for the FSP with constant pin diameter and pin length. The tool rotational speed of 900 min -1 , traversing speed of 40 mm/min and tilt 2°, respectively, kept constant for all the experiments. Macro, optical micro images and micro hardness tests were used to evaluate the particle distribution. Powder agglomeration was observed in the retreating side of samples processed with 16 mm and 18 mm shoulder diameter tools. On the other hand, significant improvement in particle distribution and excellent bonding with the substrate were observed for the sample processed with 20 mm shoulder diameter tool. The findings of this investigation are important and provide knowledge for better tool design and effective tool selection to bring out better distribution in a single pass. Keywords: friction stir processing, aluminium alloy, shoulder diameter, microstructure V tem prispevku avtorji opisujejo izdelavo in raziskavo izdelanega nanokompozita s kovinsko osnovo (angl.: SMMCs; Surface Metal Matrics Composites) na povr{ini aluminijeve zlitine vrste AA6063, izdelanega s pomo~jo vrtilno (rotacijsko) trenjskega procesa (angl.: FSP; Friction Stir Processing). Vsi vzorci povr{inskega kompozita {irine 2 mm in globine 2 mm so bili izdelani vzdol`sredi{~ne linije kovinske plo{~e. Pri tem so bili med FSP dodajani pribli`no 80 nm delci TiB2 prahu v nastajajo~e brazde. Za za~etno prekrivanje in kompaktiranje brazd napolnjenih s TiB2 so uporabili orodje brez trna in s tem prepre~ili razpr{evanje delcev med FSP. Za izdelavo SMMCs so uporabili dr`ala razli~nih premerov (16, 18, in 20) mm z valj~ki, name{~enimi na povr{ini dr`al, ki so se vrteli v nasprotni smeri urnega kazalca. Pri tem so za FSP uporabili trn s konstantnim premerom in dol`ino. Pri vseh preizkusih so za izbrani FSP uporabili hitrost vrtenja 900 min -1 , vzdol`no hitrost potovanja orodja 40 mm/min, in nagib 2°. Da bi ugotovili porazdelitev delcev TiB2 v izdelanih SMMCs so izvedli metalografske preiskave in dolo~ili mikrotrdoto kompozitov. Opazili so aglomeracijo pra{nih delcev na vzorcih izdelanih s 16 mm in 18 mm premerom dr`ala orodja. Po drugi strani pa so dosegli pomembno izbolj{anje porazdelitve pra{nih delcev in njihovo odli~no vezavo s kovinsko osnovo pri vzorcih, ki so bili izdelani z 20 mm premerom dr`ala orodja. Ugotovitve te raziskave omogo~ajo bolj{e oblikovanje in u~inkovito izbiro orodja za doseganje optimalne porazdelitve nanodelcev v kovinski osnovi pri FSP z enim samim prehodom F. Klju~ne besede: proce...

Effect of Tool Shoulder-to-Pin Diameter Ratio (D/d) on the Mechanical Properties of Friction Stir Processed Mg-Micro Al₂O₃ Composite

“…Figure 4(b) shows the observation using an 18 mm-diameter tool shoulder in which the stirred zone is shinier, indicating that the reinforced particles mixed in better with Mg AZ91A compared to FSPed Mg-Micro Al2O3 composite using a 20 mm-diameter tool shoulder. It is applicable that the tool shoulder diameter is important to enhance material flow and obtain adequate particle distribution [26]. However, there was also a tunnel defect on the surface.…”