Tensile ductility improvement of AlSi9Cu1 alloy by chemical composition optimization

Abstract

Diesel engines are used more and more widely in North America and Europe for passenger cars and light trucks because of their high fuel efficiency and reduced greenhouse gas emissions. These diesel engine components require a higher tensile property due to higher compression ratio and maximum breakout pressure of diesel engine compared with gasoline engines. Despite many advantages in the development of aluminum alloys, the alloys currently used for gasoline engine parts, typically A356 and 319 alloys, cannot meet the demand for high heat resistance [1][2][3][4][5] . In our previous work [6] , we studied the influence of the secondary dendrite arm spacing (SDAS) as well as the combination of the SDAS and the heat treatment parameters on the mechanical properties of a cylinder head of A356 alloy. We found that the A356 alloy cylinder head with smaller SDAS reached its peak value Abstract: Diesel engines, characterized by higher breakout pressure and compression ratio in comparison with gasoline engines, require particularly elevated tensile properties for their engine parts. In order to maintain both high strength and high ductility in the cylinder head, i.e., to obtain higher percent elongation without further reducing the tensile strength, AlSi9Cu1 alloy was used to prepare the cylinder head in an aluminum diesel engine. At the same time, the effect of different modification elements, Na or Sr, and Fe content on the reduction of secondary dendrite arm spacing (SDAS) was discussed, and the design of T7 heat treatment parameters were analyzed in order to improve the tensile ductility. The result shows: (1) The SDAS is as small as 18±3 µm for the Sr modified alloy. (2) The percent elongation of the alloy with Sr modification increases by 66.7% and 42.9%, respectively, compared with the unmodified alloy and the alloy with Na modification. (3) Lower Fe content alloy (0.10%) gives good results in percent elongation compared to the alloy with higher Fe content (0.27%); in particular, after Sr modification and T7 heat treatment, the elongation of over 5% is obtained. of hardness (HB), ultimate tensile strength (UTS) and yield strength (YS) at a lower aging temperature, but the over-aged structure was also yielded earlier. One of the most important factors that limit the use of A356 alloy for diesel cylinder head is its lower tensile properties at elevated temperatures: the properties of A356 (without Cu) alloy deteriorate seriously when temperature reaches 250 °C [1][2][3][4][5] . The diesel cylinder head being developed requires an optimum combination of strength and elongation: UTS ≥ 290 MPa, YS ≥ 240 MPa, percent elongation ≥4.5% and HB from 95 to 125, and for gravity casting, a value of SDAS not higher than 25 micron in the combustion chamber. To meet these requirements, we selected a candidate alloy containing copper -AlSi9Cu1 to produce the diesel cylinder head. The chemical compositions of the commercial AlSi9Cu1 are very similar to alloy 354 of the AFS (the American Foundrymen's Society). It is an alloy used by...

Effect of Temperature on Deformation and Fatigue Behaviour of A356–T7 Cast Aluminium Alloys Used in High Specific Power IC Engine Cylinder Heads

“…Azadi et al [35] studied the low cycle fatigue properties of the peak aged A356 -T6 alloy with significantly lower copper addition (0.01%) and on comparison, the fatigue lives reported at 250 • C are significantly lower at comparable strain levels in relation to the overaged A356 + 0.5% Cu-T7 alloy studied here. The fatigue lives at lower temperature of 200 • C are comparable however indicating the potentially improved fatigue lives of the A356 alloy with higher copper content at elevated temperatures similar to improved monotonic deformation properties at temperatures above 250 • C as reported in various other studies [6,7].…”

“…A356 cast aluminium alloys are often used owing to their good castability, high strength and toughness while also having less susceptibility to casting defects in complex structures like cylinder heads [4,5]. A356 alloys with added Cu, like the material of interest in this study: A356 + 0.5% Cu, are used in structures like cylinder heads as they provide improved high temperature strength especially in the 200-250 • C temperature range owing to the precipitation of Al 2 Cu precipitates without significant reduction in ductility [6][7][8]. Other alloying elements are added in trace amounts to influence the shape, size and morphology of the secondary precipitates, to improve the strength and fatigue life of the material structure [9].…”

Experiment and Conformation of Non-sinusoidal Oscillation Waveform Function for Continuous Casting Mold

“…However, the maximum acceleration was larger, which would result the bigger inertia force of the oscillator and influence the movement stability. Meng, 23,24) Sun 25) and Zhang et al 26) also determined the five section functions, and the acceleration curves had the inflecting points, which was unhelpful to run smoothly for the oscillator. Zhang et al 27,28) proposed the seven section functions, which aimed at reducing the maximum acceleration, but the parameters were too many and it was inconvenient to control and optimization.…”