Friction stir processing

About: Friction stir processing is a research topic. Over the lifetime, 2977 publications have been published within this topic receiving 62158 citations.

Stress corrosion cracking susceptibility of ultrafine grained Al–Mg–Sc alloy

Abstract: General corrosion and stress corrosion cracking (SCC) behavior of coarse grained, fine grained and ultrafine grained (UFG) AA5083 and Al–Mg–Sc–Zr alloy in different thermomechanical conditions were studied in the present work. Friction stir processing (FSP) was carried out to refine the grain size. The average grain size achieved after FSP for AA5083 was 7±3 μm, whereas that for Al–4Mg–0.8Sc–0.08Zr was 0.39±0.16 μm with 100% UFG microstructure. Linear polarization resistance and cyclic polarization techniques were used to study general corrosion behavior of these alloys in 3.5 wt% NaCl solution. The UFG microstructure showed the highest polarization resistance ( R p ) of ∼93 kΩ which increased to ∼160 kΩ after 24 h of exposure in chloride solution. The peak aged Al–Mg–0.8Sc–0.08Zr showed the most positive breakdown potential with passivity in the range of −800 to −600 mV vs SCE. A power law type relationship was observed between grain size and R p for Al–Mg alloys. SCC susceptibility was estimated in 3.5 wt% NaCl solution using slow strain rate testing (SSRT) at initial strain rate of 10 −6 s −1 .The parent AA5083 alloy showed moderate susceptibility while the FSP AA5083 microstructure showed no susceptibility. The UFG Al–Mg–0.8Sc–0.08Zr condition showed >55% loss in ductility when tested in chloride solution.

Effects of nanometric inclusions on the microstructural characteristics and strengthening of a friction-stir processed aluminum–magnesium alloy

Abstract: An aluminum–magnesium alloy was friction-stir processed in the presence of TiO2 nanoparticles which were pre-placed in a groove on the surface to produce a composite. Field emission-scanning and transmission electron microscopy studies show that solid state chemical reactions occur between the Al–Mg matrix and the ceramic particles upon the severe plastic deformation process. The microstructure of the aluminum alloy consists of a coarse grain structure, large complex (Fe,Mn,Cr)3SiAl12 particles, and small Mg2Si precipitates. After friction stir processing, a deformed grain structure containing rod-like Al–Fe–Mn–Si precipitates is attained, along with cuboidal (~100 nm) Cr2 precipitates and spherical (~100 and 5 nm) Mg2Si particles. In the presence of TiO2 nanoparticles, magnesium oxide (MgO) and titanium aluminide (Al3Ti) nanophases are formed. It is shown that these microstructural modifications lead to a significant enhancement in the hardness and tensile strength of the aluminum alloy. The relationship between the microstructural evolution and mechanical properties and the role of hard inclusions are presented and discussed. An analysis based on strengthening models indicates that the yield strength of the nanocomposite is mainly controlled by dislocations and grain boundaries rather than the nano-scale inclusions.