**3. Experimental work**

Experimental work starts with the preparation of work pieces to be joined. Each work-piece of the base material of size 300 × 150 × 6.35 mm by power hacksaw cutting and milling. Configuration of the square butt joints is prepared to make FSW joints. The unique joint configuration is achieved by using mechanical clamps to secure the plates in place. The welding direction is normal for the rolling direction. The joints are manufactured using a single pass welding procedure. Non-consumable tools made of tungsten carbide material are utilized to fabricate the joints. **Tables 1** and **2** show the chemical composition and mechanical characteristics of base metal.

**Vertimach V-350**. Vertical Machining Centre is used to fabricate the required joints**.** Three distinctive tool pin profiles are utilized to create the joints as appeared in **Figure 3** and nearly 81 joints are manufactured to study the impact of tool pin profile, rotational velocity, welding velocity and axial force on stir welded AA6061 aluminum alloy tensile properties. **Table 3** shows the levels of the experiment based on the Taguchi method. The experimental results are shown in **Tables 4–6**.

**137**

*Experimental Investigations on AA 6061 Alloy Welded Joints by Friction Stir Welding*

**Mn Si Fe Cu Cr Zr Mg Ti Al** 1.2 0.8 0.7 0.4 0.35 0.25 0.15 0.15 Balance

> **Elongation (%)**

276 310 18 12.24 105

**Reduction in crosssectional area (%)**

**Hardness (VHN)**

Using power hacksaw, the welded joints are sliced and then tensile specimens are machined to the necessary sizes. Guidelines for the preparation of sample samples are followed by the American Society for Testing of Materials (ASTM). In 400 KN, Electro-Mechanical Controlled Universal Testing Machine Tensile test has been carried. The specimen is recorded when the neck fails and the load versus the displacement. Charpy Impact Test is also conducted for the specimens. The Rockwell Hardness Test is conducted by indenting the test material with a diamond cone indenter. The indenter is compelled into tare using a Light Optical Microscope (Make: NIKON-LV 150) built into an Image Analysis Software. The specimens for metallographic examination are divided into FSP, TMAZ, HAZ and base metal areas according to the necessary dimensions. The samples are polished using various grades of emery documents. Final polishing is performed in the Disc Polishing Machine

**Process parameters Symbol Units Level 1 Level 2 Level 3** Tool rotational speed N rpm 1200 1600 2000 Welding speed S mm/min 48 60 72 Axial force F KN 1.5 2.0 2.5

*DOI: http://dx.doi.org/10.5772/intechopen.89797*

*AA6061 alloy (weights %) chemical composition.*

**Ultimate strength (MPa)**

**Table 1.**

**Table 2.**

**Figure 3.**

**Table 3.**

*Tool pin profiles of FSW.*

*Important factors and their levels for AA6061.*

**Yield strength (MPa)**

*AA6061 mechanical characteristics.*

*Experimental Investigations on AA 6061 Alloy Welded Joints by Friction Stir Welding DOI: http://dx.doi.org/10.5772/intechopen.89797*


#### **Table 1.**

*Aluminium Alloys and Composites*

defect-free FSP is very limited.

parameters

**Figure 2.**

joints.

**3. Experimental work**

because of the heat produced by the friction and the metal flow through the stirring action. On the other hand, owing to incorrect metal flow and inadequate metal consolidation in the FSP region, FSW Joints are susceptible to other defects such as cracks, tunnel defect, kissing bond, piping defect, pin hole, etc. Existing literature focuses on the impact of welding parameters and tool profiles on the formation of

*Different regions of FSW joint. A = unaffected metal base; B = Heat Affected Zone (HAZ); C = Thermo-*

**Objectives of this present work**: a Solemn attempt is made in the present investigation to conquer the limitations identified and to conduct experimentation

1.To fabricate FSW joints with different tool pin profiles and identify the process

2.Investigation of the impact of tool pin profile and welding parameters (rotational speed, welding speed and axial force) on the formation of defect-free FSP as well as on tensile, impact properties and the hardness of the welded

3.The ANN modelling of the process and to attain maximum tensile strength and

Experimental work starts with the preparation of work pieces to be joined. Each work-piece of the base material of size 300 × 150 × 6.35 mm by power hacksaw cutting and milling. Configuration of the square butt joints is prepared to make FSW joints. The unique joint configuration is achieved by using mechanical clamps to secure the plates in place. The welding direction is normal for the rolling direction. The joints are manufactured using a single pass welding procedure. Non-consumable tools made of tungsten carbide material are utilized to fabricate the joints. **Tables 1** and **2** show the

**Vertimach V-350**. Vertical Machining Centre is used to fabricate the required joints**.** Three distinctive tool pin profiles are utilized to create the joints as appeared in **Figure 3** and nearly 81 joints are manufactured to study the impact of tool pin profile, rotational velocity, welding velocity and axial force on stir welded AA6061 aluminum alloy tensile properties. **Table 3** shows the levels of the experiment based

on the Taguchi method. The experimental results are shown in **Tables 4–6**.

4.Evaluation of the microstructure of FSP zone for different pin profiles.

on AA6061 Al alloys with the objectives as given in the following:

*Mechanically Affected Zone (TMAZ); D = Friction Stir Processed (FSP) zone.*

analysis of variance for optimal process parameters.

5.Conducting the SEM analysis to analyse the flow of material.

chemical composition and mechanical characteristics of base metal.

**136**

*AA6061 alloy (weights %) chemical composition.*


#### **Table 2.**

*AA6061 mechanical characteristics.*

#### **Figure 3.**

*Tool pin profiles of FSW.*


#### **Table 3.**

*Important factors and their levels for AA6061.*

Using power hacksaw, the welded joints are sliced and then tensile specimens are machined to the necessary sizes. Guidelines for the preparation of sample samples are followed by the American Society for Testing of Materials (ASTM). In 400 KN, Electro-Mechanical Controlled Universal Testing Machine Tensile test has been carried. The specimen is recorded when the neck fails and the load versus the displacement. Charpy Impact Test is also conducted for the specimens. The Rockwell Hardness Test is conducted by indenting the test material with a diamond cone indenter. The indenter is compelled into tare using a Light Optical Microscope (Make: NIKON-LV 150) built into an Image Analysis Software. The specimens for metallographic examination are divided into FSP, TMAZ, HAZ and base metal areas according to the necessary dimensions. The samples are polished using various grades of emery documents. Final polishing is performed in the Disc Polishing Machine


#### **Table 4.**

*Optimum parameters for the threaded pin profile.*


#### **Table 5.**

*Optimum parameters for the conical pin profile.*


#### **Table 6.**

*Optimum parameters for the triangular pin profile.*

using the diamond compound (1 mm particle size). Specimens are etched with the Keller's reagent, to reveal the macro and micro structures. SEM analysis is conducted using the Scanning Electron Microscope. SEM produces a range of signals exterior of sample specimens by utilizing the high energy focused electrons. Signals derived from SEM reveal information on the sample, including exterior morphology (texture), chemical composition, crystalline structure and orientation of the sample material.
