Iranian Journal of Materials Science and Engineering

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In this study, Al2014 alloy refined with Al-5%Ti-1%B master alloy was prepared by strain-induced melt activated (SIMA) process. The main variables of the SIMA process were cold working, holding time and temperature in semi-solid state. Cold working was applied on specimens by upsetting technique to achieve 10%, 20% and 30% height reduction. Cold worked specimens were heat treated in semi-solid state at 585 °C, 595 °C, 605 °C, 615 °C, 625 °C and 635 °C and were kept in these temperatures for different times (20 and 30 min). Observations through optical and scanning electron microscopy were used to study the microstructural evaluation. The results revealed that fine and globular microstructures are obtained by applying 30 % height reduction percentage and heat treating in 625 °C for 30 min. Comparison between refined and unrefined Al2014 alloy after applying SIMA process showed that Al-5%Ti-1%B master alloy has no significant effect on average globule size but makes the final structure more globular.

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The influence of different heat treatment parameters, namely solutionizing and artificial
aging conditions, on the microstructure, mechanical hardness, and corrosion resistance of Al-
12Si-Cu alloy are systematically explored in this work. Solution treatment was performed at
two temperatures (500°C and 530°C) and two durations (0.5 and 3 hours), and artificial aging
was made at two temperatures (180°C and 310°C) over two durations (2 and 5 hours).
Optical microscopy also showed interesting microstructural changes with fine grain
refinement and enhanced spheroidization of the coarse eutectic Si phase and a more uniform
distribution of primary intermetallic grains. These structural adjustments were identified as
direct determinants of properties of the material. Maximum microhardness (155 HV) was
achieved at the temperatures of 500°C/3 h solutionizing and 180°C for 5 h aging (S3), which
was ascribed to successful solid solution strengthening and fine precipitation hardening. In
contrast, the lowest hardness (54 HV) was obtained at the values 530°C/3 h + 310°C/5 h (S8),
showing the harmful impact of over-aging at higher temperatures. Analysis of
electrochemical corrosion detected a significant correlation between the corrosion resistance
and treated microstructure, where conditions favoring microstructural refinement resulted in a
decrease in corrosion current density. A Design of Experiments (DOE) method by way of the
Taguchi L8 orthogonal array was used to find out how each parameter contributed relative to
the other variable. The analysis revealed that, whilst the aging temperature was the most
influential factor to the microhardness, the solution time was the controlling factor on the
surface roughness. The results demonstrate a robust determination of the main processing
windows which are known to be crucial to enhance particular properties and verify the
tremendous feasibility of temperature control in heat treatment process optimization in
engineering the necessary trade-off between mechanical strength and corrosion performance
in Al-12Si-Cu alloys.