Friction stir processing of nanofiller assisted AISI 1010 steel-CDA 101 copper dissimilar welds: a strength factor approach

Abstract

In this research study the effects of adding nano fillers such as SiO2, graphene nanoplatelets (Gnps) and biochar on to the weld pool of dissimilar AISI-SAE 1010 Steel- CDA 101 copper were investigated. The main aim of this research study was to investigate the effect of adding ceramic and carbon rich secondary reinforcements on to the friction stir weld (FSW) pool of dissimilar metals and its relative outcomes. The mechanical properties such as tensile strength, yield strength, % of elongation, hardness and fatigue strength were investigated in the form of the strength factor approach. According to the results, the highest strength factor of 98 was obtained for welds made using Gnps of about 1.0 wt.% with constant axial load of 5 kN, traverse speed of 30 mm/min, rotational speed of 900 rpm, dwell time of 5 s and plunging depth of 0.2 mm. The highest tensile strength of 225 MPa and a fatigue strength of 168 MPa was noted for the weld using 2 wt.% Gnps in the weld pool. However, the biochar addition of 2.0 wt.% on to the weld bead positioned the second highest strength factor of 88 due to its solid lubricity. In all the welding processes, large doses of fillers produced undesirable strength factor values. The microstructure of both the weld and tool shows desirable effects for nanoparticle assisted welds. The HAZ and TMAZ grains were refined due to the inclusion of the nanoparticles. The result shows that naturally acquired biochar nanoparticles have the potential of replacing high cost nanofillers in joining metals with more than 85% close to the high cost fillers for the same output. These properties improved dissimilar copper-steel welded plate joints that could be used in automotive, defence, aerospace and structural applications.

Impact of tool-related parameters during fabrication of dissimilar AISI 1010 – CDA 101 joints by FSW

“…The presence of these brittle natured intermetallic compounds had contributed for supplementary brittleness in the zone of stir, thereby reducing the strength and elongation percentage of the fabricated defect-free weldment, due to which attainment of the strengths equivalent to at least one of the parent materials had become impossible [50]. At the same time, this exhibited tensile strength of 181 MPa, which is nearly 77% of one of the base material, namely CDA 101, along with a percentage of elongation of 14.01% can be considered as an appreciable strength, especially w.r.t dissimilar joints [38,51].…”

“…Lower volumes of heat input occur mainly due to low contact area between surface of tool shoulder and workpiece region. Likewise, high speed of travel of the tool (i.e., high speed of welding), will also generate inadequate heat input, provoking inappropriate mixing of dissimilar materials (i.e., AISI 1010 & CDA 101 in our case), leading to flaws like voids [38].…”

Investigation on the distribution and role of intermetallic aggregates in influencing the mechanical strength of the friction stir welded AZ91C Mg – AA6061 Al alloy joints

“…At the same time, despite these merits, FSW process involves intensified deformation of materials at peak temperatures, thereby the fabricated weldment comprises a convoluted flow of material in their weld regions. In addition to this, during the employment of FSW to join Mg-Al alloys, alloys of Mg and Al due to the experience of peak temperatures in the nugget zone, may lead to the formation of brittle, hard type Al 12 Mg 17 and Al 3 Mg 2 intermetallic aggregates and may eventually lead to cracks thereby, declining the strength of the fabricated Mg-Al alloy joint [22]. To the authors' best awareness, only a few researchers have carried out experimental investigations w.r.t joining of Mg-Al alloys using the FSW process and the majority of these research investigations have been focused on the impact of process parameters like the spinning speed of the tool, rate of tool traverse, the geometry of employed tool, etc on the mechanical properties of the fabricated weldment.…”