Understanding the Mechanical Response of Friction Stir Welded …
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near-uniform distribution of the reinforcing titanium diboride TiB 2 particles through
the metal matrix.
Percentage elongation is a measure for ductility of the chosen material. Experimental results revealed the elongation to be higher for the case of Tool Variant # 1
and subsequently decreases for the Tool Variant # 2. The peak elongation was 6.91%
for a tool rotational speed of 708 rpm and a tool welding speed of 20 mm/min. While
a lowest ductility of 5.82% was encountered for a tool rotational speed of 931 rpm
and a tool welding speed of 40 mm/min. Percentage elongation of the base composite
material, i.e., the 3%TiB 2 /Al-12Si was 8.8%, while peak elongation of the friction stir
welded joint was 6.91%. This helps conclude that elongation is noticeably reduced
by 21.47% due to welding.
The indentation or microhardness is the hardness of a material that is exposed
to a lower range of applied loads. It provides a measure of the resistance to indentation of the composite material. A larger and deeper indentation signifies a lower
hardness value of the material. The weld joint specimens were tested at different
positions around the stirring zone and an average value was recorded for the purpose
of calculation. The Tool Variant # 2 demonstrates a peak value of the microhardness to be 90.1 HV for a tool shoulder diameter of 20 mm, a tool rotational speed
of 931 rpm and a tool welding speed of 20 mm/min. The in situ 3%TiB 2 /Al-12Si
composites possess a microhardness of 71.5 HV and the peak microhardness for
all possible combinations of welding parameters was as high as 90.1 HV. The test
results confirm that friction stir welding does contribute to enhancing the hardness of
the welded joints, which can essentially be attributed to a stirring mechanism that is
facilitated or caused by the rotating tool probe. The rotations tend to both refine and
uniformly distribute the reinforcing TiB 2 particulates through the aluminum alloy
(i.e., Al-Si) metal matrix.
Main Effect Plots
The main effect plot for the test data is shown in Fig. 6 with respect to (i) tool variant,
(ii) tool rotational speed, and (iii) tool welding speed. This graph was generated with
the help of MINITAB software using the analysis of variance (ANOVA) technique.
The following are the key findings.
(a) It was observed that the mean value of ultimate tensile strength decreases as
diameter changes from Tool Variant # 1 with a diameter of 18 mm to Tool
Variant # 2 with a diameter 20 mm. Also, a similar pattern was observed for the
case of tool welding speed from 20 to 40 mm/min and the tool rotational speed
from 708 to 931 rpm.
(b) The elongation revealed an observable decrease from Tool Variant # 1 of diameter 18 mm to the Tool Variant # 2 of diameter 20 mm. Also, the data mean or
average revealed an observable decrease from a welding speed of 20 mm/min
53
near-uniform distribution of the reinforcing titanium diboride TiB 2 particles through
the metal matrix.
Percentage elongation is a measure for ductility of the chosen material. Experimental results revealed the elongation to be higher for the case of Tool Variant # 1
and subsequently decreases for the Tool Variant # 2. The peak elongation was 6.91%
for a tool rotational speed of 708 rpm and a tool welding speed of 20 mm/min. While
a lowest ductility of 5.82% was encountered for a tool rotational speed of 931 rpm
and a tool welding speed of 40 mm/min. Percentage elongation of the base composite
material, i.e., the 3%TiB 2 /Al-12Si was 8.8%, while peak elongation of the friction stir
welded joint was 6.91%. This helps conclude that elongation is noticeably reduced
by 21.47% due to welding.
The indentation or microhardness is the hardness of a material that is exposed
to a lower range of applied loads. It provides a measure of the resistance to indentation of the composite material. A larger and deeper indentation signifies a lower
hardness value of the material. The weld joint specimens were tested at different
positions around the stirring zone and an average value was recorded for the purpose
of calculation. The Tool Variant # 2 demonstrates a peak value of the microhardness to be 90.1 HV for a tool shoulder diameter of 20 mm, a tool rotational speed
of 931 rpm and a tool welding speed of 20 mm/min. The in situ 3%TiB 2 /Al-12Si
composites possess a microhardness of 71.5 HV and the peak microhardness for
all possible combinations of welding parameters was as high as 90.1 HV. The test
results confirm that friction stir welding does contribute to enhancing the hardness of
the welded joints, which can essentially be attributed to a stirring mechanism that is
facilitated or caused by the rotating tool probe. The rotations tend to both refine and
uniformly distribute the reinforcing TiB 2 particulates through the aluminum alloy
(i.e., Al-Si) metal matrix.
Main Effect Plots
The main effect plot for the test data is shown in Fig. 6 with respect to (i) tool variant,
(ii) tool rotational speed, and (iii) tool welding speed. This graph was generated with
the help of MINITAB software using the analysis of variance (ANOVA) technique.
The following are the key findings.
(a) It was observed that the mean value of ultimate tensile strength decreases as
diameter changes from Tool Variant # 1 with a diameter of 18 mm to Tool
Variant # 2 with a diameter 20 mm. Also, a similar pattern was observed for the
case of tool welding speed from 20 to 40 mm/min and the tool rotational speed
from 708 to 931 rpm.
(b) The elongation revealed an observable decrease from Tool Variant # 1 of diameter 18 mm to the Tool Variant # 2 of diameter 20 mm. Also, the data mean or
average revealed an observable decrease from a welding speed of 20 mm/min