Figure 5.

(a) Area indented by HV tester in Al-2.0 wt.% Fe sample, (b) deformed region shown under higher magnification.

15 micro-indentations made on the weld fillets and between the weld fillets, as

OM image in the cross section of Al-Fe sample laser-treated, indicating the depths selected for microhardness

Effect of Microstructure on Microhardness and Electrochemical Behavior in Hypereutectic…

Region Average of HV Standard deviation of VH

On the weld fillets 52.68 6.18 Between the weld fillets 59.14 5.53

in the matrix that extends throughout the recast area, as can be checked in

Al-2.0 wt.% Fe alloy, while previous studies by Pariona et al. [2–4] involved hypoeutectic Al-1.5 wt.% Fe alloy. Although both alloys were castings and solidified by laser-treated process in the same conditions, however, microstructural analysis of the two alloys revealed characteristics different. The overlapping line of consecutive weld fillets at the cast zone of Al-1.5 wt.% Fe alloy was barely perceptible than Al-2.0 wt.% Fe alloy. In addition, also in the cast zone, presence of protuberances on the weld fillets was much more noticeable at Al-1.5 wt.% Fe alloy than at Al-2.0 wt. % Fe alloy. However, Al-1.5 wt.% Fe alloy showed a behavior lamellar at the cast zone and meanwhile Al-2.0 wt.% Fe alloy showed a behavior fine-columnar-like structure. Both alloys showed nanopores, which were concentrated mostly on the weld fillets. The microhardness of Al-2.0 wt.% Fe alloy LSR-treated surface was

slightly more higher than Al-1.5 wt.% Fe alloy.

Present study focused on the microstructural characterization of hypereutectic

As can be seen in Table 3, the HV values measured on the sample surface are consistent with those measured in the cross-section too, so showing a higher average hardness at the region between the weld fillets than on the weld fillet. Pariona et al. [3], who made a comparative analysis of the HV of Al-1.5 wt.% Fe alloy measured on the weld fillets and between the weld fillets, also reported that the hardness between the weld fillets was higher than on the weld fillets, therefore, the surface hardness in the laser-treated region in relation to the untreated region is high, due to the treated region morphology is more homogeneous, without presence of intermetallic phase (Al3Fe) and with the presence of Al6Fe phase finely dispersed

Analysis of Vickers hardness on the treated sample surface, indicating the hardness at the regions on the weld

indicated in Table 3.

fillets and between the weld fillets (VH 0.1 15 s).

DOI: http://dx.doi.org/10.5772/intechopen.81095

Figure 7.

Table 3.

measurements.

Figures 2–4.

183

#### Figure 6.

Vickers hardness analysis (HV 100 gf, 15 s) of LSR-treated layer and untreated substrate.


#### Table 2.

Vickers hardness analysis in a cross-sectional area, in sample treated and untreated (HV 100 gf, 15 s).

involving LSR treatment of materials, similar results have been obtained by Yao et al. [19] and others, who reported a significant increase in hardness in lasertreated region than untreated region.

The material surface hardness was also analyzed by HV measurements on the weld fillets region and between them (see Figures 2–4), for the as-received laser-treated sample. The average Vickers hardness was calculated for

Effect of Microstructure on Microhardness and Electrochemical Behavior in Hypereutectic… DOI: http://dx.doi.org/10.5772/intechopen.81095

#### Figure 7.

OM image in the cross section of Al-Fe sample laser-treated, indicating the depths selected for microhardness measurements.


#### Table 3.

Analysis of Vickers hardness on the treated sample surface, indicating the hardness at the regions on the weld fillets and between the weld fillets (VH 0.1 15 s).

15 micro-indentations made on the weld fillets and between the weld fillets, as indicated in Table 3.

As can be seen in Table 3, the HV values measured on the sample surface are consistent with those measured in the cross-section too, so showing a higher average hardness at the region between the weld fillets than on the weld fillet. Pariona et al. [3], who made a comparative analysis of the HV of Al-1.5 wt.% Fe alloy measured on the weld fillets and between the weld fillets, also reported that the hardness between the weld fillets was higher than on the weld fillets, therefore, the surface hardness in the laser-treated region in relation to the untreated region is high, due to the treated region morphology is more homogeneous, without presence of intermetallic phase (Al3Fe) and with the presence of Al6Fe phase finely dispersed in the matrix that extends throughout the recast area, as can be checked in Figures 2–4.

Present study focused on the microstructural characterization of hypereutectic Al-2.0 wt.% Fe alloy, while previous studies by Pariona et al. [2–4] involved hypoeutectic Al-1.5 wt.% Fe alloy. Although both alloys were castings and solidified by laser-treated process in the same conditions, however, microstructural analysis of the two alloys revealed characteristics different. The overlapping line of consecutive weld fillets at the cast zone of Al-1.5 wt.% Fe alloy was barely perceptible than Al-2.0 wt.% Fe alloy. In addition, also in the cast zone, presence of protuberances on the weld fillets was much more noticeable at Al-1.5 wt.% Fe alloy than at Al-2.0 wt. % Fe alloy. However, Al-1.5 wt.% Fe alloy showed a behavior lamellar at the cast zone and meanwhile Al-2.0 wt.% Fe alloy showed a behavior fine-columnar-like structure. Both alloys showed nanopores, which were concentrated mostly on the weld fillets. The microhardness of Al-2.0 wt.% Fe alloy LSR-treated surface was slightly more higher than Al-1.5 wt.% Fe alloy.

involving LSR treatment of materials, similar results have been obtained by Yao et al. [19] and others, who reported a significant increase in hardness in laser-

Vickers hardness analysis in a cross-sectional area, in sample treated and untreated (HV 100 gf, 15 s).

Region Depth of the surface Average of VH Standard deviation of VH

100 μm 60.0 3.8 200 μm 57.4 3.0

500 μm 35.2 1.44 700 μm 35.4 1.68

Treated region 50 μm 59.0 3.15

Untreated region 300 μm 36.5 1.43

(a) Area indented by HV tester in Al-2.0 wt.% Fe sample, (b) deformed region shown under higher

The material surface hardness was also analyzed by HV measurements on the weld fillets region and between them (see Figures 2–4), for the as-received

laser-treated sample. The average Vickers hardness was calculated for

Vickers hardness analysis (HV 100 gf, 15 s) of LSR-treated layer and untreated substrate.

treated region than untreated region.

Figure 5.

Figure 6.

Table 2.

182

magnification.

Aerospace Engineering
