PSI - Issue 33

Rizki Dwi Ardika et al. / Procedia Structural Integrity 33 (2021) 171–180 Author name / Structural Integrity Procedia 00 (2019) 000–000

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6. Cause formation of porosity Porosity is a significant problem in the welding process because it can cause a decrease in the strength of the weld joint. Differences influence the formation of porosity in the welding process in the solubility of hydrogen between molten aluminum alloys and solid aluminum alloys (Huang et al., 2018). The formation of porosity is very complex and is influenced by the coupling effects of metallurgical solidification and fluid mechanics (Ryan et al., 2018). In the welding process, porosity defects can occur and cause stress concentrations. The porosity that often occurs in laser welding is metallurgical porosity caused by hydrogen in the molten pool (Han et al., 2020). Apart from hydrogen, which can cause porosity, environmental factors also influence porosity (Pequet et al., 2002). The environments that affect porosity are air temperature, air humidity, and dissolved oxygen (Ahsan et al., 2016). Arc current and high heat input conditions in the welding process also affect porosity's appearance (Ascari et al., 2012) (Ahsan et al., 2016). 7. Impact of porosity on mechanical properties of welded joints Porosity has an impact on decreasing mechanical properties which causes a decrease in the ductility of the weld joint, thus affecting the fracture mode when fatigue failure occurs. (Ferreira et al., 1999). In addition to reducing the mechanical properties of welding, porosity can minimize fatigue stress and significantly reduce the weld joint's strength (S. Wu et al., 2019). Porosity can reduce the welded joint's effectiveness and reduce the tensile strength in the fusion region (Leo et al., 2015). The porosity distribution also affects the mechanical properties of welded joints using selective laser melting, indicating that porosity damages the lower surface at fatigue stress performance (Yang et al., 2018). Research on the effect of porosity on welding has continued to progress and has become an exciting study in recent years. The discussion topics for porosity in welding are very diverse, including the weld metal's microstructure, the use of different materials, the mechanical properties of the weld joint, and many others. Table 1 summarizes several research articles on porosity that focus on discussing the effect of porosity on welded joint.

Table 1. Study of porosity in welding with a discussion of the impact of porosity on mechanical properties in welded joints.

No. Scholars

Material

Method

Subject

Finding

Gou et al. (2015)

A7N01S-T5 aluminum alloy

welded joints for high-speed trains

Effect on microstructural porosity and fatigue strength of the A7N01S T5 aluminum alloy weld joint Effect of welding parameters on the porosity distribution, the correlation between the porosity distribution and mechanical properties 6082-T6 aluminum alloy welding joint of moisture

Increased humidity causes an increase in porosity and causes a decrease in fatigue strength at the weld joint Porosity appears around the fusion zone when the arc current of the weld exceeds 140 A. The rate of gas flow affect the porosity. The tensile strength decreased from 260 MPa to 202 MPa, the fatigue strength decreased from 113 MPa to 56 MPa, and the weld joint became brittle as the porosity rate increased. The hardness value decreases as the heat input value decreases. A significant decrease in hardness occurs in the bottom welding area due to differences in heat input values that trigger porosity, and grain size change.

1

2

Han et al. (2020)

6082-T6 aluminum alloy

laser-MIG hybrid welding

3

Samiuddin et al. 2020

Aluminum alloy Al-5083

tungsten inert gas welding (TIG)

Effect and compaction cracks on TIG AA 5083 welding of porosity