TESTING 1-2-3
Advancing Aluminum T
Researchers aim to develop a new alloy to maximize performance of cylinder heads in diesel engines. A MODERN CASTING STAFF REPORT
wo major incentives exist for the automotive manufacturing industry to improve efficiency. Te first is customer pull: Who doesn’t want
more power while simultaneously minimizing gasoline consumption? Secondly, increasing environmental regulation from governments around the world aim to reduce the environ- mental impact of passenger car trans- portation. Tese two competing forces have led car manufacturers to reduce engine displacement and weight while maintaining performance, mainly through the use of direct fuel injection systems and turbochargers. Tese technological improvements,
however, mean higher operating tem- peratures and higher pressures, leading to increased thermo-mechanical stress, particularly on the valve bridge
ADDING IT ALL UP Breaking down the latest research is as easy as 1-2-3.
“Alloy Development for Highly Stressed Diesel Engine Cylinder Heads,” Bruno Bourassa and Danny Jean, Rio Tinto Alcan, Arvida Research and Development Center, Jonquiere, Quebec, Canada; and J. Fred Major, Kingston, Ontario, Canada
1
2 3
Background—Researchers investigated a possible alloy based on the 2xx series. Like the 201 or A/B206 families, this alloy provides high levels of strength and ductility. The addition of vanadium and zirconium increased the alloy’s creep resistance. Also, while low levels of titanium in the B206 alloy has improved castability and hot tear resistance, titanium was used in a high temperature alloy variant to help increase creep resistance.
Procedure—Six versions of alloy 224 were prepared in a 77.2-lb. (35-kg) electrical resistance tilting furnace. Tensile test bars were cast and T7 heat treated before tensile testing was conducted.
Results and Conclusions—The 224 alloy variant with 0.15% Mg had the high- est strength across all temperature ranges in comparison to the other alloys. In general, Al-Cu-based alloys performed better in general terms compared to conventional Al-Si based alloys, though the higher strength of the Al-Cu alloys limits ductility. Still, the 224 alloys provided best results considering both strength and ductility.
between inlet and exhaust ports on the combustion face of the cylinder heads. Te development of a new aluminum alloy, one that could increase perfor- mance without associated problems related to hot tearing, could be an avenue that addresses the two, often competing demands faced by automo- tive manufacturers. Such an alloy also may lead to uses in other applications in other industries. Researchers Bruno Bourassa and
Danny Jean, Rio Tinto Alcan, Arvida Research and Development Cen- ter, Jonquiere, Quebec, Canada; and J. Fred Major, Kingston, Ontario, Canada, investigated a possible alloy based on the 200 series and published their findings in the paper, “Alloy Development for Highly Stressed Diesel Engine Cylinder Heads.” Like the 201 or A/B206 families, this alloy provides high levels of strength and
ductility. Te addition of vanadium and zirconium increased the alloy’s creep resistance. Also, while low levels of titanium in the B206 alloy has improved castability and hot tear resistance, titanium was used in a high temperature alloy variant to help increase creep resistance.
Question Can a new generation of aluminum
alloy based on the 200 series be devel- oped to improve strength, ductility and creep resistance?
1 Background
Since manufacturers began using aluminum for diesel engine cylinder heads, four generations of alloy have been
developed. Te primary A356 or A357 was pressed into service when thermal fatigue cracks were encountered in gasoline engines. Tis first generation was an alternative to the common 319-320 alloys. Te second generation began with
the development of the A356+0.5% copper alloy. Currently this is the stan- dard for diesel engine cylinder heads in Europe and has made inroads in the North American market. Te addi- tion of 0.5% copper increases the high temperature strength without notably decreasing the ductility or thermal conductivity. Next, zirconium and manganese
were added to the A356+0.5% copper alloy as dispersoid formers to inhibit creep. Tis development tested well but is considered evolutionary rather than revolutionary. It may help with existing designs, but it is not seen as something that allows for a significant leap in design capabilities. From the opposite end of the
spectrum, a fourth generation alloy has been developed based on A319/A320
March 2015 MODERN CASTING | 45
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