Improving element uniformity and mechanical properties of Al-Mg-Si alloy fabricated by twin roll casting with superheat melt treatment

The effect of superheat melt treatment(SMT) on microstructure and properties of Al-Mg-Si alloy fabricated by twin roll casting(TRC) was analyzed using optical microscope, scanning electron microscopy, emission electron probe micro analyzer and transmission electron microscopy. SMT increased the subcooling degree of melt during TRC. The solidification microstructure with high dendrite density and small dendrite spacing was obtained. The second phase was evenly distributed between dendrites and the solute concentration gradient was decreased. Intergranular solute aggregation caused by Reynolds’ dilatancy in TRC slab was effectively suppressed. The homogeneous solute distribution of TRC slab with SMT can be realized by short-time homogenization heat treatment. The size of insoluble particles was greatly reduced. The complete decomposition of non-equilibrium eutectic phase increased the solute concentration in α-Al, which promoted the precipitation of precipitates during aging heat treatment. The tensile strength and yield strength of T6 slab were improved, while the uniform elongation are almost not decreased. The strength and uniform of slab in T4P state were both improved. The obtained results can help further shorten the production cycle of TRC slabs and improve mechanical properties.

High-Shear De-Gassing and De-Ironing of an Aluminum Casting Alloy Made Directly from Aluminum End-of-Life Vehicle Scrap

High-shear melt conditioning (HSMC) technology was used for degassing and de-ironing of an aluminum alloy recovered from the Zorba cast fraction of the non-ferrous scrap from shredded end-of-life vehicles. The results showed that the recovery of aluminum alloys from the Zorba cast fraction was more than 80%. High-shear melt conditioning improved the degassing process during melt treatment in comparison with the adding of degassing tablets. The efficiency of the de-ironing process using HSMC increased by up to 24% after, increasing the Mn content to 0.8% in the melt. Adding Mn to Zorba melt enhanced the de-ironing process and eliminated the formation of β-AlFeSi intermetallic particles, which have a detrimental effect on both the mechanical and corrosion properties of the alloy.

Investigation of the Nodularisation Propensity of Calcined Cashew-Nut Shell-Ash in Cast-Iron Melt Graphite

Production of ductile iron using ferrosilicon-magnesium master alloy in melt treatment is currently fraught with challenges bothering on cost and availability. In this study the suitability of cashew nut shells ash (CNSA) as a viable alternative to magnesium master alloys employed in the treatment of molten cast iron for enhanced mechanical properties was studied. The carbonized CNSA used varied from 2-10 wt. % to treat different heat batches; CA1-CA5 containing varied amount of CNSA, CaO and FeSi in the molten cast iron. The cast samples were subjected to both mechanical characterisation (tensile, hardness and impact) and microstructural analysis using Instron electromechanical machine, impact tester and scanning electron microscope (SEM) coupled with energy dispersive spectroscope (EDS). Results show that the 8 wt. % CNSA addition demonstrated the best mechanical properties comparable to ASTM A536 ferritic ductile cast iron. Specifically, the 8 wt. % CNSA cast samples exhibited 433 MPa tensile strength, 144HRC hardness and ductility of 14.7%. Contributions to improved mechanical properties may be attributed to the development of sufficient fractions of graphite nodules during melt treatment with CNSA. These outcomes are a boost both to the production of quality ductile irons and a cleaner environment. Keywords: Nodularisation, ductile-iron, cashew-nut, ferrosilicon-magnesium alloy, mechanical properties

Improvement of the secondary aluminium metallurgical quality by means of an adequate melt treatment.

This work has the purpose to demonstrate that if an adequate melt treatment is applied, it is pos-sible to obtain recycled aluminium alloy AlSi10MnMg(Fe) with as good metal cleanliness than primary AlSi10MnMg alloy. The melt quality is assessed by the thermal analysis, density index, macro- and micro-inclusions tests, of one primary and two secondary alloys, before and after the melt treatment. The melt treatment is based on deoxidation, degassing and skimming with de-tailed procedure described in this article. The different analysis are: Thermal analysis to compare the variables of the solidification cooling curve (Al primary temperature and its undercooling; Al-Si eutectic temperature and its recalescence); Density index is used to evaluate the hydrogen gas content in the melt; Macroinclusions level is analysed after solidifying the melt under vacuum of 5 mbar, favouring inclusion floatation to the sample surface; Microinclusion level is evaluate with porous disc filtration apparatus (similar to PoDFA).