Gm Global Technolgoy Operations, Inc.

University of Missouri

Surender Maddela

Blair E Carlson

David R Sigler

Matthew J O'Keefe

Hong-Hsiang Kuo

Yar-Ming Wang

Thomas J O'Keefe

Jane G O'Keefe, Legal Representative

A weld joint is disclosed that weld bonds together an aluminum workpiece and a steel workpiece. The weld joint includes an aluminum weld nugget, an intermetallic layer, and an annular ring of aluminide particles that is selected from the group consisting of nickel aluminide particles, iron aluminide particles, and a combination thereof. The annular ring of aluminide particles extends upwards from a weld bond surface of the weld joint such that the annular ring of aluminide particles extends radially inwardly into the aluminum weld nugget and protects the weld bond surface of the weld joint against crack propagation that may originate from a notch root of the weld joint.

Al-steel weld joint

A method of resistance spot welding an aluminum workpiece and an adjacent overlapping steel workpiece is disclosed in which a source of a reactive metal in a diffusible state is located along a faying interface of an aluminum workpiece and an adjacent overlapping steel workpiece. The source of the reactive metal in a diffusible state may take on a variety of forms including (1) a composite adhesive layer that includes reactive particles dispersed throughout a structural thermosetting adhesive matrix or (1) a reactive alloy layer that confronts and is in proximate contact with a faying surface of the aluminum workpiece. Once the source of a reactive material in a diffusible state is in place and the workpiece stack-up is assembled, an electrical current is passed through the workpiece stack-up and between a set of opposed welding electrodes at a weld zone to ultimately produce a weld joint.

Method of resistance spot welding aluminum to steel

A method for testing an electrochemical response of a sample, which is at least partially disposed within an electrolyte, includes macro scanning the sample. Macro scanning is applied across the entire sample and includes applying a first range of macro potential between the electrolyte and the sample, and measuring a first range of macro current between the electrolyte and the sample, while subject to the first range of macro potential. The macro scan is held at a first fixed macro potential within the first range of macro potential and the sample is micro scanned while held at the first fixed macro potential. Micro scanning is applied at individual points across a surface portion of the sample and includes measuring a plurality of first micro currents at each of the individual points of the surface portion of the sample. Each individual point is significantly smaller than the entire sample.

Electrochemical testing for corrosion analysis

A method for forming an adhesion promoting layer and a corrosion resistant layer over the surfaces of a body-in-white ('BIW') structure is provided. The method includes immersing the BIW structure in a pre-activating bath to pre-activate the surfaces of the BIW structure. The surfaces of the BIW structure comprise at least an aluminum alloy surface, at least a surface comprising ferrous metal, zinc, or TiZr, and the surfaces are substantially free of magnesium alloys. An adhesion promoting layer comprising cerium and a corrosion resistant layer comprising polymers are subsequently deposited over the pre-activated surfaces of the BIW structure by immersing the BIW structure in an aqueous bath comprising a source of cerium cations and a polymer precursor.

Method of coating body-in-white structure having at least one surface comprising an aluminum alloy

Mixed-metal automotive vehicle bodies-in-white comprising ferrous metal surfaces, zinc surfaces, aluminum alloy surfaces, and magnesium alloy surfaces are cleaned and immersed in an aqueous bath comprising an adhesion promoter and an aqueous electrocoat bath (the adhesion promoter may be in the electrocoat bath. The adhesion promoter, which may be a cerium salt, is selected to react with each metal in the body surfaces to form an oxide layer that provides corrosion resistance for the surface and adherence for the deposited polymeric paint coating. The body is cathodic in the electrocoat deposition.

Growing community of inventors

Rochester Hills, MI, United States of America

Surender Maddela