Generation of force and torque during joining of AZ91C plates by FSW under distinctive tool tilt angle and their impact on mechanical strength and micro-structure

Abstract

Joint characteristics of friction stir welded AZ91C Mg alloy flat plates in terms of mechanical strength and micro-structural attributed have been investigated by varying the tool tilt angles for two distinctive tapered tool pin geometries without and with threaded structures (TP and TPWT). Spindle torque and distinctive forces acting longitudinally, vertically (termed as X and Y – force respectively) generated at the interface of the tool and flat plates were measured and analyzed to understand the impact of employed tool tilt angles. It was revealed that the spindle torque and forces relevant to FSW escalates with the increase in tool tilt angle. Spindle torque (15.1 Nm) and Y–force (6.4 kN) generated by TPWT are higher than that of TP tool (11 Nm and 2 kN), whereas X – force associated with TPWT (0.74 kN) tool was found to be lower when compared to that of the TP tool (0.98 kN). Inconsistencies in forces have escalated with a simultaneous escalation in the tool tilt angle for the TP tool and the TPWT tool has exhibited a reversed behavior. Enhanced flow of plasticized metal induced by tool pin geometry with threaded structures have contributed to the formations of onion ring type features and these structures cannot be visualized in the joints fabricated by the TP tool. The largest value of tensile strength of 227 MPa was exhibited by joint fabricated at 0° tool tilt angle using TPWT tool.

Keywords:

• Tool tilt angle
• AZ91C Mg alloy
• friction stir welding
• tool pin geometry
• spindle torque
• welding force

Disclosure statement

No potential competing interest was reported by the authors.