Search Results

We have studied the formability of continuous strip cast (CC) AA5754 aluminum alloy for automotive applications. Strip casting technology can considerably reduce material cost compared with conventional direct chill (DC) cast aluminum sheets. However, the CC material tends to exhibit much less post-localization deformation and lower fracture strains compared with DC sheets with similar Fe content, although both alloys show similar strains for the onset of localization. Bendability of the CC alloy is also found to be inferior. The inferior behavior (post-necking and bendability) of the CC alloy can be attributed to the higher incidence of stringer-type particle distributions in the alloy. The formability of the AA5754 alloy has also been studied using two dimensional microstructure-based finite element modeling. The microstructures are represented by grains and experimentally measured particle distributions.

A family of low-cost, creep-resistant magnesium alloys has been developed. These alloys, containing aluminum, calcium, and strontium are designated as “ACX” alloys. Developed for engine blocks and transmissions, the “ACX” alloys have at least 40% greater tensile and 25% greater compressive creep resistance than AE42, and corrosion resistance as good as AZ91D (GMPG 9540P/B corrosion test). These alloys are estimated to cost only slightly more than AZ91D and have as good castability. Creep data up to 200°C, tensile properties at room temperature and 175°C, corrosion results and microstructure analysis are presented and discussed. These alloys have the potential to enable the extension of the substantial weight reduction benefits of magnesium to powertrain components.

A new core binder system (1) was used to produce foundry cores for casting hollow aluminum suspension parts by the low pressure, gravity flow, semi-permanent mold method. These and other prototype aluminum parts made using the system demonstrate that easy core removal from complex castings, core and sand recycling, and an improved environment in the core making facilities will increase productivity, improve product quality and reduce manufacturing costs.

The presence of marred and scratched areas detract from the appearance of current automotive topcoat systems. Although the final determination of the extent of the damage to the paint surfaces must be made by human visual evaluation, machine estimation of this damage has value in being a tool for screening large numbers of different paint technologies. Scattered light from marred regions (both single and multiple scratches) in an automotive basecoat/clearcoat system was generated and collected in a goniophotometer. The areas under the intensity/angle curves were obtained using an extended trapezoidal rule for numerical integration. This technique shows promise in correlating goniophotometric data with human evaluation of marred areas. This technique may be of value in screening different paint technologies and chemistries.

This paper describes a bench method to evaluate the frictional behavior, under scuffing conditions, of some test coupons of standard materials currently used in making cylinder bores and pistons. The usefulness of this method is in evaluating new materials and coatings that may enable the elimination of iron liners from engine blocks. While investigating the potential application of Plasma Source Ion Implantation (PSII) on engine piston/bore materials, we have systematically studied the scuffing related friction behavior of aluminum 390 alloy and cast iron. A pin-on-disk tribometer is used under dry sliding conditions. Testing parameters for simulating cold scuff in bench tests have been specified. This proposed test method offers a screening tool desirable for the development of PSII technology and may also be useful for the design of other new surface modification techniques.

This paper examines the potential use of diamond-like carbon (DLC) on aluminum alloy pistons of internal combustion engines. Our approach is to apply a DLC coating on the piston running against an aluminum-390 bore thus eliminating the iron liners in a standard piston/bore system. Experimental data, using a pin-on-disk tribometer under unlubricated test conditions, indicate that the performance of the DLC coating against aluminum 390 exhibits superior friction resistance compared to aluminum-390 against cast iron; the latter material couple representing the materials currently being used in production for the piston/bore application. Moreover, by thermally cycling the DLC coatings we show that improved friction and wear properties can he maintained to temperatures as high as 400°C.