![Figure 3: Heat input at various welding speeds used to weld 6.35 mm thick AA 7075-T7351 plates using MX-Triflute, MX-Trivex and Trivex tools [44].](/figures/figure-3-heat-input-at-various-welding-speeds-used-to-weld-6-3jvy4hs2.webp)
![Figure 30: Hardness as a function of the distance from the FSW weld centreline; the horizontal line indicates the starting hardness. The upper limit of the shaded region corresponds to the slowest rotation speed and vice–versa. (a) Welded in the as–quenched martensitic state. (b) Welded after rolling the martensite to a 35% cold reduction. (c) Changes in the grain size within the stir zone. Adapted from [182].](/figures/figure-30-hardness-as-a-function-of-the-distance-from-the-kjbhriix.webp)
![Figure 17: Streamlines for isothermal model [47] that used a limiting shear stress of 40 MPa: a) Triflute tool, b) single streamline for Triflute tool showing vertical movement and c) Trivex tool. Tool rotation 457 rpm and translation at 457 mmmin−1.](/figures/figure-17-streamlines-for-isothermal-model-47-that-used-a-2hy8jrb4.webp)
![Figure 8: Analogy between chip morphology in machining and material flow in FSW [79]. Midplane horizontal sections of AA 7075-T6 show the re-distribution of copper about the center-line after welding when copper foil is placed between the plates to be welded. Tool was made of C40 Steel, with shoulder diameter of 12 mm. The cylindrical pin had a dimeter of 3.0 mm while the conical pin had a major diameter equal to 5.00 mm and minor diameter of 1.90 mm and both were 2.70 mm in height (for the conical pin, this corresponds to cone angle 30◦).](/figures/figure-8-analogy-between-chip-morphology-in-machining-and-15vawahg.webp)
![Figure 14: Variation of dimensionless peak temperature [102] with non-dimensional heat input.](/figures/figure-14-variation-of-dimensionless-peak-temperature-102-1x8izole.webp)
Q2. What contributions have the authors mentioned in the paper "Recent advances in friction stir welding – process, weldment structure and properties" ?
This review deals with the fundamental understanding of the process and its metallurgical consequences.
Q3. What is the way to estimate the peak temperature of a workpiece?
Dimensional analysis, a useful tool for understanding a complex situation, can be used to estimate peak temperature in the workpiece using available numerically computed and experimentally measured thermal cycles for different alloys [102].
Q4. What are the main independent variables that are used to control the FSW process?
The welding speed, the tool rotational speed, the vertical pressure on the tool, the tilt angle of the tool and the tool design are the main independent variables that are used to control the FSW process.
Q5. Why did Ya et al. use Moiré interferometry incremental-hole drilling?
Since diffraction is expensive and conventional hole-drilling is only suited to uniform plane stress around the hole, Ya et al. [132] used Moiré interferometry incremental-hole drilling method to assess residual stress in a friction stir weld.
Q6. How do you determine the final positions of the weld?
One way to understand material flow experimentally is to use inert markers before starting the weld [77], and then determine their final positions using serial sectioning parallel to the top surface.
Q7. What is the main obstacle for tailoring weld attributes based on fundamental scientific principles?
the lack of reliability is not the only obstacle for tailoring weld attributes based on fundamental scientific principles.
Q8. What is the likely cause of the austenite to recrystallise?
It is likely that the severe deformation in this zone causes the austenite to recrystallise, perhaps repeatedly, prior to its transformation during subsequent cooling.
Q9. What is the reason for the ferrite grain boundaries being rough?
The austenite grain boundaries also become rough during deformation and this adds to their potency as heterogeneous nucleation sites; shear bands are introduced which are additional locations for ferrite formation.
Q10. Why does the torque increase with the increase in traverse speed?
The torque increases only slightly with the increase in traverse speed because material flow becomes somewhat more difficult at slightly lower temperatures.
Q11. What is the effect of deformation on the heat generation rate?
In the context of heating resulting from plastic deformation, the decrease in the yield strength with increasing temperature leads to a reduction in the heat generation rate by this mechanism.
Q12. What is the tangential speed of the tool with respect to the workpiece?
At any point on the tool workpiece interface, the tangential speed of the tool with respect to the workpiece is given by vr = ωr − U sin θ where r is the radial distance from the tool-axis and θ is the angle between radial vector, r, and the welding direction.
Q13. Why do steels have a high temperature during friction stir welding?
because they tend to be mechanically weak, the temperatures reached during friction stir welding are not particularly high.
Q14. What is the importance of convective heat transfer in the FSW?
even for a high thermal conductivity material such as aluminium, convective heat transfer is an important mechanism for heat transfer near the tool during FSW.
Q15. What is the impact of friction stir welding on the performance of the steel?
Friction stir welding must clearly disrupt the base microstructure both through the thermal and deformation components of the process [174] but the consequences of this on performance during fabrication and service need investigation.
Q16. What is the reason for the lack of a grossly deformed microstructure?
Given that the TMAZ of steel welds does not contain a grossly deformed microstructure, there should be no detrimental corrosion property associated with friction stir welding.