Nazatul Liana Sukiman

Durability and Corrosion of Aluminium and Its Alloys: Overview, Property Space, Techniques and Developments

Aluminium (Al) is an important structural engineering material, its usage ranking only behind ferrous alloys (Birbilis, Muster et al. 2011). The growth in usage and production of Al continues to increase (Davis 1999). The extensive use of Al lies in its strength:density ratio, toughness, and to some degree, its corrosion resistance. From a corrosion perspec‐ tive, which is most relevant to this chapter, Al has been a successful metal used in a num‐ ber of applications from commodity roles, to structural components of aircraft. A number of Al alloys can be satisfactorily deployed in environmental/atmospheric conditions in their conventional form, leaving the corrosion protection industry to focus on market needs in more demanding applications (such as those which require coating systems, for example, the aerospace industry).

Imparting Sensitization Resistance to an Al-5Mg Alloy via Neodymium Additions

Low-level Nd additions, up to 0.17 wt%, were added to Al-5Mg to explore the impact on the subsequent degree of sensitization. Following heat treatment at 150°C for 1 day and 7 days, nitric acid mass loss (NAMLT) tests revealed that additions of >0.11% Nd were effective at decreasing the amount of subsequent intergranular attack.

Influence of microalloying additions on Al–Mg alloy. Part 1: Corrosion and electrochemical response

Abstract A range of custom alloys based on the Al–4Mg–0·4Mn system were produced with selected quaternary microalloying additions. Alloying elements studied include silicon, zinc, lead, titanium, tin, zirconium, strontium and neodymium. To characterise the corrosion response, electrochemical tests were carried out in 0·1M NaCl, supplemented by constant immersion tests and basic microstructural characterisation by means of scanning electron microscopy (SEM). Optical profilometery was used to determine the form and intensity of localised corrosion. The results indicate that low level quaternary alloying additions can have a marked influence on specific aspects of the first order correlation between chemistry, microstructure, hardness and corrosion.

Influence of microalloying additions on Al-Mg alloy. Part 2: Phase analysis and sensitisation behaviour

Abstract A range of alloys based on the Al-4Mg-0·4Mn system were produced with selected quaternary microalloying additions. In Part 1 of this study, the electrochemical and corrosion response was studied. To characterise the sensitisation behaviour of these alloys, where sensitisation is the major mode of degradation of 5xxx alloys, heat treatment at 150°C was carried out and followed by the Nitric Acid Mass Loss Test (NAMLT) according to ASTM G67-04. Herein the alloying elements studied include silicon, zinc, titanium, zirconium and strontium. The results indicate that strontium (Sr), silicon (Si) and titanium (Ti) have a significant influence in reducing intergranular corrosion (IGC) susceptibility.

Impact toughness, hardness and shear strength of Fe and Bi added Sn-1Ag-0.5Cu lead-free solders

In this study, the new Fe/Bi-bearing Sn-1Ag-0.5Cu (SAC105) solder alloys were studied for their mechanical properties, including impact toughness, hardness and shear strength. Charpy impact tester with impact speed of 5.4 m/s was used to determine the impact absorbed energy during impact tests. With the 0.05 wt.% Fe and 1 wt.% Bi addition to the SAC105 alloy, the impact absorbed energy increased from 8.1 J to 9.7 J by about 20% and literally no further improvement was observed by increasing the Bi content in the alloy. Vickers hardness tests were performed with a load of 245.2 mN and load dwell time of 10 s. The addition of Fe/Bi to SAC105 increased the hardness of the alloy from 10.5 HV to 22.6 HV showing an increase of more than two fold. Shear tests were performed with a shear speed of 0.25 mm/min. Shear strength almost doubled for the Fe/Bi added SAC105, as compared to the base alloy, increasing from 17.8 MPa to 34.3 MPa. The microstructure study shows that Bi is dissolved in the solder bulk and strengthens the solder alloys by its solid solution strengthening mechanism. The β-Sn grain size, as revealed by cross-polarized optical microscopy, significantly reduced from 60–100 μm to 20–40 μm with Fe/Bi addition to SAC105. The micrographs of field emission scanning electron microscopy (FESEM) with backscattered electron detector and their further analysis via ImageJ software indicated that Fe/Bi addition to SAC105 significantly reduced the Ag3Sn and Cu6Sn5 IMCs size and refined the microstructure. These changes in the microstructure of Fe/Bi added SAC105 expectedly resulted in such improvement in their mechanical properties.

Microstructural and tensile properties of Fe and Bi added Sn-1Ag-0.5Cu solder alloy under high temperature environment

Abstract In this work, the iron (Fe) and bismuth (Bi) added (0.05 wt% Fe and 1 wt% or 2 wt% Bi) Sn-1Ag-0.5Cu (SAC105) lead-free solder alloys were prepared and their microstructure and tensile properties under severe thermal environments were extensively investigated and compared with the base alloy SAC105. The isothermal aging was done at 200 °C for 100 h, 200 h, and 300 h. Fe/Bi added SAC105 showed a significant reduction in the IMCs size (Ag3Sn and Cu6Sn5), especially the Cu6Sn5 IMCs and a refinement in the microstructure, which is due to the existence of Bi in the alloys. Moreover, the existence of Fe and Bi gives the microstructure better stability under severe thermal aging conditions. The tensile testing results showed that the addition of Fe and Bi to SAC105 greatly improves yield stress and tensile strength, but decreases ductility level, which is because of the Bi solid solution strengthening mechanism. Under severe thermal aging, the Fe/Bi added SAC105 showed more stable tensile properties, because of the existence of both Fe and Bi in the alloys.