TESTING 1-2-3 Advancing Aluminum


Researchers aim to develop a new alloy to maximize performance of cylinder heads in diesel engines.


T 1


2 3


AN MCDP STAFF REPORT


wo major incentives exist for the automotive manufactur- ing industry to improve effi ciency. T e fi rst 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 environmental impact of passen- ger car transportation. T ese 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.


T ese technological improvements, however, mean higher operating temperatures and higher pressures, leading to increased thermo-mechanical stress, particularly on the valve bridge between inlet and exhaust ports on the combustion face of the cylinder heads. T e development of a new aluminum alloy, one that could increase performance without associated problems related to hot tearing, could be an avenue that addresses the two, often competing demands faced by automotive manufactur- ers. 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 Center, Jonquiere, Quebec, Canada; and J. Fred Major, Kingston, Ontario, Canada, investigated a possible alloy based on the 200 series and published


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 De- velopment Center, Jonquiere, Quebec, Canada; and J. Fred Major, Kingston, Ontario, Canada


Background—Researchers investigated an alloy based on the 2xx series. The addition of vanadium and zirconium increased the al- loy’s creep resistance. Also, while low le vels 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 highest strength across all temperature ranges in comparison to the other alloys. In general, Al-Cu-based alloys performed better compared to conventional Al-Si based alloys, though the higher strength of the Al-Cu alloys limits ductility. Still, the 224 alloys pro- vided best results considering both strength and ductility. ■


36 | METAL CASTING DESIGN & PURCHASING | Jul/Aug 2015


their fi ndings in the paper, “Alloy De- velopment for Highly Stressed Diesel Engine Cylinder Heads.” Like the 201 or A/B206 families, this alloy provides high levels of strength and ductility. T e 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. T e primary A356 or A357 was pressed into service when thermal fatigue cracks were encountered in gasoline engines. T is fi rst generation was an alternative to the common 319- 320 alloys. T e second generation began with


the development of the A356+0.5% cop- per alloy. Currently this is the standard for diesel engine cylinder heads in Eu- rope and has made inroads in the North American market. T e addition 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. T is development tested well but is considered evolutionary rather than revolutionary. It may help with existing


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