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Effect of arc stud welding parameters on the microstructure and mechanical properties of AA6061 and AA5086 aluminium alloys

Razzaq M. K. A., Abood A. N.

Journal of Achievements in Materials and Manufacturing Engineering

2021

Vol. 108, nr 1

24--34

Purpose: This paper aims to investigate the effect of arc stud welding (ASW) process parameters on the microstructure and mechanical properties of AA6061-T6 and AA5086-H116 joint. Design/methodology/approach: ASW process was done with argon as a shielding gas. Optical microscope (OM), scanning electron microscope (SEM), and X-Ray Diffraction (XRD) were employed to investigate the influence of welding current, welding time, and gas flow-rate on the microstructure of the fusion zone (FZ). Torque strength and Microhardness tests were used to evaluate the mechanical properties of the welded joints. Findings: OM and SEM showed a cellular dendritic structure with equiaxed zone and columnar dendritic are forming at welding zone and weld interface. XRD analysis showed the precipitation of Mg2Si and Al3Mg2 in the similar and dissimilar joints. Similar ASW of AA6061-T6/AA6061-T6 recorded 19 N.m torque strength, while dissimilar welding of AA6061-T6/AA5086-H116 registered 23 N.m. With increasing heat input, grains in Fusion Zone (FZ) and Heat Affected Zone (HAZ) coarsen and the hardness in both zones decreased. The hardness of similar weldments indicated a remarkable softening of FZ, while lower hardness values were registered in HAZ of dissimilar weldments. Softening of both weldments is due to the dissolution of the strengthening precipitates. Hot cracks exist with similar weldments, while no cracks evidence with dissimilar weldments. Research limitations/implications: The main challenge in this work was how to minimize porosity level and how to avoid hot crack in the FZ. Practical implications: The application of ASW with ceramic ferrule has an important role in different production areas such as; automobile industry, aircraft applications, and appliances industry. Originality/value: Study the effect of welding current, welding time, and gas flow-rate of ASW process on microstructure and mechanical properties of AA6061-T6 and AA5086-H116 joint.

The effect of annealing and anisotropic behaviour on tensile and fatigue properties of AA 8090

Abass M. H., Mahmud F., Alali M. S., Abood A. N.

Archives of Materials Science and Engineering

2019

Vol. 99, nr 1/2

5--12

Purpose: This paper aims to assess microstructures and mechanical properties of annealed and un-annealed Al-Li alloys (AA8090) and provide valid information regarding influence of anisotropy on tensile properties, fatigue lives. Design/methodology/approach: The methodology included investigating the influence of annealing on grain size, tensile strength and fatigue lives of AA8090. Optical microscope, scanning electron microscope and X-ray diffraction were utilized to analyse the crystallographic texture. Findings: The results showed that the un-annealed alloy exhibited much finer grain structure in three directions, namely longitudinal (L) rolling direction, L-45° and Long transverse (LT) combined with stronger crystallographic texture. Regarding to mechanical properties, un-annealed alloy presented superior tensile strength with strong anisotropic behaviour. L and LT grains direction showed highest tensile strength value of 550 MPa and L-45° showed lowest tensile strength value of 420 MPa. Results of fatigue test revealed that annealed Al-Li alloy has lower fatigue lives with high influence of test direction on fatigue properties. Higher variation in fatigue life to failure links with un-annealed alloy over annealed alloy. Examination of fractured surface showed that the morphology of fractured surface is a mixture of ductile and brittle fractures in both annealed and un-annealed alloys with more brittle behaviour in un-annealed alloy. Research limitations/implications: The main challenge of this work is the determination of the test direction (test angle in respect to rolling direction), which is necessary to provide correct information regarding mechanical properties. Further study of low cycle fatigue can be done in future, which will be an excellent indication to mechanical properties of this alloy since it provides more understanding to the behaviour of the material and better comprehend crack propagation and strain stress concentration. Practical implications: AA8090 alloy is an important candidate for aerospace and aircraft industries. Influence of annealing heat treatment and rolling direction on mechanical properties of AA8090 alloy provides more accurate information to the manufacturers who deal with this alloy. Originality/value: This study is affording a significant information regarding the effect of annealing and anisotropic behaviour on mechanical properties of AA8090. To our knowledge, there are few reports that study this combination of factors on AA8090 alloy.