Grain Refinement and Improvement in Microhardness of AZ91 Mg …
205
Table 1 Comparison of microhardnes of FSPed AZ91 without aluminum powder SP and DP with
380 and 545 rpm with untreated die-cast AZ91 Mg alloy
SR No.
Specimen
condition
Specimen 1
hardness
Vickers HV
Specimen 2
hardness
Vickers HV
Specimen 3
hardness
Vickers HV
Average
hardness
Vickers HV
1
Die-cast AZ91
Mg alloy
84.64
84.83
84.50
84.66
2
AZ91 FSP 380
SP without Al
91.50
93.65
90.20
91.78
3
AZ91 FSP 545
SP without Al
93.90
91.73
96.69
94.10
4
AZ91 FSP 380
DP without Al
105.90
104.76
99.22
103.29
5
AZ91 FSP 545
DP without Al
102.05
101.57
105.52
103.05
3.3 Microhardness and Grain Size Study
3.3.1 Microhardness
Comparison of microhardness of FSPed AZ91 without aluminum powder SP and DP
with 380 and 545 rpm with untreated die-cast AZ91 Mg alloy is shown in Table 1.
The average hardness of the as-received die-cast AZ91 Mg alloy was 84 HV. FSP
380 and 545 rpm and SP without aluminum powder AZ91 Mg alloy specimens have
hardness in range of 91–94 HV, while FSP 380 and 545 rpm and DP without aluminum
powder AZ91 Mg alloys have microhardness in range of 103 HV. This is because
grain refinement takes place due to double pass which increases microhardness of
DP-treated specimens.
Same way, microhardness comparison was done with FSP at 380 and 545 rpm,
SP and DP with aluminum powder specimens and compared with untreated diecast AZ91 Mg alloy as shown in Fig. 17. Here, FSP 380 and 545 rpm and SP with
aluminum powder AZ91 Mg alloy specimens have hardness in range of 105–106
HV, while FSP 380 and 545 rpm and DP without aluminum powder AZ91 Mg alloys
have microhardness in range of 115–116 HV (Table 2).
Ghader has worked on AZ91/Al 2 O 3 nanocomposites and proved that FSP DP has
higher hardness due to decreasing grain size [12].
3.3.2 Grain Size Measurement of Specimens
As shown in Table 3, comparison of grain size of FSPed AZ91 without aluminum
powder SP and DP with 380 and 545 rpm with untreated die-cast AZ91 Mg alloy
was done. Die-cast AZ91 Mg alloy has average gain diameter of 37.8 μm, while due
to FSP SP at 380 and 545 rpm rotational speed, grain refinement took place from
205
Table 1 Comparison of microhardnes of FSPed AZ91 without aluminum powder SP and DP with
380 and 545 rpm with untreated die-cast AZ91 Mg alloy
SR No.
Specimen
condition
Specimen 1
hardness
Vickers HV
Specimen 2
hardness
Vickers HV
Specimen 3
hardness
Vickers HV
Average
hardness
Vickers HV
1
Die-cast AZ91
Mg alloy
84.64
84.83
84.50
84.66
2
AZ91 FSP 380
SP without Al
91.50
93.65
90.20
91.78
3
AZ91 FSP 545
SP without Al
93.90
91.73
96.69
94.10
4
AZ91 FSP 380
DP without Al
105.90
104.76
99.22
103.29
5
AZ91 FSP 545
DP without Al
102.05
101.57
105.52
103.05
3.3 Microhardness and Grain Size Study
3.3.1 Microhardness
Comparison of microhardness of FSPed AZ91 without aluminum powder SP and DP
with 380 and 545 rpm with untreated die-cast AZ91 Mg alloy is shown in Table 1.
The average hardness of the as-received die-cast AZ91 Mg alloy was 84 HV. FSP
380 and 545 rpm and SP without aluminum powder AZ91 Mg alloy specimens have
hardness in range of 91–94 HV, while FSP 380 and 545 rpm and DP without aluminum
powder AZ91 Mg alloys have microhardness in range of 103 HV. This is because
grain refinement takes place due to double pass which increases microhardness of
DP-treated specimens.
Same way, microhardness comparison was done with FSP at 380 and 545 rpm,
SP and DP with aluminum powder specimens and compared with untreated diecast AZ91 Mg alloy as shown in Fig. 17. Here, FSP 380 and 545 rpm and SP with
aluminum powder AZ91 Mg alloy specimens have hardness in range of 105–106
HV, while FSP 380 and 545 rpm and DP without aluminum powder AZ91 Mg alloys
have microhardness in range of 115–116 HV (Table 2).
Ghader has worked on AZ91/Al 2 O 3 nanocomposites and proved that FSP DP has
higher hardness due to decreasing grain size [12].
3.3.2 Grain Size Measurement of Specimens
As shown in Table 3, comparison of grain size of FSPed AZ91 without aluminum
powder SP and DP with 380 and 545 rpm with untreated die-cast AZ91 Mg alloy
was done. Die-cast AZ91 Mg alloy has average gain diameter of 37.8 μm, while due
to FSP SP at 380 and 545 rpm rotational speed, grain refinement took place from