Yucel Birol

Cooling slope casting to produce EN AW 6082 forging stock for manufacture of suspension components

The potential of cooling slope casting process to produce EN AW 6082 forging stock for the manufacture of EN AW 6082 suspension components was investigated. EN AW 6082 billets cast over a cooling plate offer a fine uniform structure that can be forged even without a separate homogenization treatment. This is made it possible by the limited superheat of the melt at the start of casting and the fractional solidification that occurs already on the cooling plate. Suspension parts forged from cast and homogenized billets with or without Cr all showed a uniform structure, and the hardness reached HV 110 after the standard artificial ageing treatment.

Effect of iron on microstructure and mechanical properties of primary AlSi7Mg0.3 alloy

Abstract Effect of Fe on microstructure and mechanical properties of the primary AlSi7Mg0.3 alloy and the potential of Mn addition to counteract any adverse effects was investigated in the present work. The primary AlSi7Mg0.3 is a better alloy than its counterpart with twice as much Fe. β platelets grow twice as big when the Fe concentration is doubled. This, in turn, increases shrinkage porosity and leads to a 3-fold decrease in the tensile elongation values. Adding an equal amount of Mn helps to modify the β platelets into more compact α particles and also reduces shrinkage porosity. While these structural changes are reflected by a modest improvement in the mechanical properties, Mn addition fails to offer a full recovery in the ductility of the AlSi7Mg0.3 alloy. Hence, limiting the Fe content of the primary AlSi7Mg0.3 alloy to 0.12 wt% is worthwhile and pays off with superior microstructural features and mechanical properties.

Synthesis of Al−SrB6 composite via powder metallurgy processing

Abstract The potential of powder metallurgy processing for the manufacture of Al–SrB 6 composites was explored. Al 4 Sr particles fractured extensively during the ball milling of Al–15Sr/Al–4B powder mixtures. There was no interaction between the Al 4 Sr and AlB 2 compounds across the section of the aluminium grains in the as-milled state. SrB 6 formed, when the ball milled powder blends were subsequently annealed at sufficiently high temperatures. Ball milling for 1 h was sufficient for SrB 6 to become the major constituent in powder blends annealed at 700 °C while it took 2 h of ball milling for powder blends annealed at 600 °C. Higher annealing temperatures and longer ball milling time encouraged the formation of the SrB 6 compound while the latter made a great impact on the microstructural features of the Al–SrB 6 composite. The SrB 6 compound particles were much smaller and more uniformly distributed across the aluminium matrix grains in powder grains ball milled for 2 h before the annealing treatments at 600 °C and 700 °C.

Effect of Cr and Zr on the grain structure of extruded EN AW 6082 alloy

The effects of Cr and Zr addition on the coarse grain surface layer in EN AW 6082 tube extrusions were investigated. The decoration of the tube surfaces and the weld seams with coarse recrystallized grains reflects the strain as well as the temperature gradients that predominate across the section of the tubes during extrusion. The recrystallization resistance provided by Mn does not suffice to avoid the coarse surface grains. With structural features that are almost identical to those of the base 6082 alloy, the 6082 alloy with 0.06 wt% Zr also fails to offer any improvement. The coarse grain surface layer is much thinner and recrystallization is entirely avoided across the weld seams upon the addition of 0.15 wt% Cr. The superior recrystallization resistance of the revised alloy is attributed to the increase in the population of the Cr-rich Al(Cr,Mn,Fe)Si as well as (Al, Si)3Zr dispersoid particles. It is reasonable to conclude that the coaddition of Zr and Cr has a favourable impact on the resistance to recrystallization of EN AW 6082 alloy.

Effect of Vanadium and Zirconium Additions on Mechanical Properties and Microstructure of Gravity Die-Cast AlSi9Cu2 Alloy Cylinder Heads

Systematic work was performed in the present study to investigate the effect of V and Zr additions on microstructural evolution and mechanical properties of the gravity die-cast AlSi9Cu2 alloy in T6 temper. The equiaxed dendritic structure typical of AlSi9Cu2 alloy is replaced by a much finer columnar dendritic network when modified with V and Zr additions. This remarkable structural refinement is believed to be linked with the formation of the V- and Zr-containing phases that form during solidification. The co-addition of V and Zr affects the tensile properties and hardness more significantly than individual additions. While the increase in strength is accompanied by a decrease in elongation, the penalty to be paid, particularly in the case of co-addition of V and Zr, is rather small and thus could be tolerated for the superior strength in some applications.

Optimising the T6 heat treatment for gravity cast AlSi7MgCu0.5 alloy V8 cylinder heads

Abstract Alternatives to the Standard T6 heat treatment that relied on a 5-h solution heat treatment at 490 °C were investigated in effort to reduce the heat treatment cycle time for the manufacture of AlSi7MgCu0.5 alloy V8 cylinder heads without sacrificing the mechanical properties while providing extra capacity in the heat treatment plant. The optimum T6 heat treatment process was identified to be a SHT at 545 °C for 1 h followed by ageing treatment at 180 °C for 3 h. Mechanical properties of the cylinder heads thus manufactured were markedly superior while the total heat treatment duration was reduced by 2.5 h with respect to the Standard heat treatment. This implied a capacity increase of %61 and rendered the undertaking of a major customer order possible.