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Transition materials which are used to join dissimilar metals such as steel and aluminum on automobiles are described in this paper. The problems associated with conventional methods of joining these two metals include galvanic corrosion, brittle welds, reduced mechanical properties and reduced design flexibility. These problems are solved through the use of clad transition materials at the joints. Transition materials are fabricated by roll bonding dissimilar metals to form the clad materials and subsequently forming the materials to the desired configurations. The clad material allows the actual transition from one metal to the other to occur at the clad bond interface and thus only similar metal joints exist in the assembly. Welding studies describe the high strength and ductility of steel to aluminum joints through the use of steel clad aluminum transition materials.

A number of factors are considered important when considering the choice of material for light vehicle bumpers. These include economics, styling, appearance, fabricability, and durability. Additional factors are introduced due to safety, fuel efficiency and environmental issues. As these issues become more stringent, the choice of material becomes more difficult because traditional materials are not able to provide all of the required properties. This paper describes clad materials systems which provide the required properties while introducing weight reduction in bumpers. Specific combinations of stainless steel and aluminum in a clad configuration have been used on automobiles and trucks for many years in a wide range of applications. These clad metal systems have all of the desirable properties of the individual components and provide a light weight alternative to the limitations of traditional materials.

Galvanic corrosion and mechanical properties are major design considerations for bimetallic assemblies. Galvanic corrosion can lead to rapid degradation while welding of dissimilar metals such as steel and aluminum can lead to reduced structural stability. This paper describes a new concept in joining dissimilar metals involving the use of transition materials. The clad transition materials is composed of the dissimilar metals to be joined and effectively reduces the corrosion and mechanical problems associated with the system. Results of galvanic corrosion field tests and welding studies for transition materials are presented and several examples of automotive applications are cited.

1006 steel clad aluminum has been used as a transition material to directly spot weld steel to aluminum. Advantages of the clad metal transition include the ability to spot weld with existing equipment and reduction of dissimilar metal crevice corrosion at the steel-aluminum interface. Sheet steel between 0.8mm and 2.0mm has been spot welded to aluminum between 0.8mm and 3.0mm in a variety of combinations with the transition material. This paper contains specific spot welding parameters for a variety of joints containing steel and aluminum at thicknesses normally encountered in body applications. The mechanism of weld nugget formation for aluminum-transition-steel joints is evaluated. Weld lobes established according to SAE and Aluminum Association guidelines are presented. The effect of electrode design on joint strength and heat balance are discussed.

The choice of material for a particular application depends on many factors, including cost, availability, appearance, strength, fabricability, and corrosion resistance. Frequently, use of a monolithic metal is compromised by one or more of its properties. The metallurgical materials systems concept provides a means of designing specific properties into a single composite material. Two or more metals are bonded at the atomic level to form a clad metal that meets the precise requirements of a specific application. In this report technical factors involved in designing corrosion-resistance materials systems are considered. Advantages and limitations are discussed and specific automotive engineering applications are used.

A new clad metal system has been developed as a material for hydraulic brake line tubing. The material consists of a 1008 LCS/304 SS/1008 LCS composite in the ratio 45%/10%/45%. Laboratory experimental tests, accelerated life tests, and field tests were performed on brake tubing formed from this material. The results show that the brazed and ternecoat low-carbon steel/stainless steel/low-carbon steel tubing has excellent corrosion resistance and high mechanical strength. The results are compared with those obtained with conventional brazed and ternecoat LCS brake tubing.

Transition materials consisting of steel clad aluminum have been used to join aluminum and steel. This technique allows joining by resistance spot welding since the clad transition material allows the actual transition from one metal to the other to occur at the clad bond interface. Welding studies show that in the recommended range of weld parameters, high strength joints are produced. A wide range of corrosion tests have been used to determine the durability of these joints in automotive environments. Results show that the use of transition material in joining aluminum to steel or EG steel eliminates galvanic corrosion.

This paper deals with the corrosion behavior of various exterior automotive trim materials including electroplated steel, stainless steel, stainless clad aluminum and anodized aluminum. The mechanisms of corrosion are discussed, particularly with regard to external appearance and galvanic corrosion of painted auto-body steel adjacent to the trim. Field tests on the various trim materials are described including six year service performance with stainless clad aluminum. Quality control tests for these materials which are currently utilized are listed and described.

Design, fabricability, thermal, mechanical, physical and durability properties are all important to the successful application of materials systems to heat exchangers. In recent years, use of clad metals for furnace brazing of heat exchangers has increased significantly. These brazing materials have proven to be cost effective and reliable and the properties of the materials can be tailored to the heat exchanging application. The primary materials used in these applications range from copper clad steel to copper clad stainless steel. Selection of the component metals determines the properties of the materials system and therefore provides the properties desired in the heat exchanger. This paper discusses the process used to fabricate copper clad self brazing material and for brazing heat exchangers. Factors important in the selection of a particular materials systems are described and data is provided on the properties of these materials in heat exchangers.