Study of the Mechanical Joint of a Bimetallic Cross Obtained by Localized Additive Manufacturing of Fusion Applied to Automotive Transmissions

Objective: This study aims to investigate the joining region between two materials — a steel produced by additive manufacturing and a rolled aluminum — with the purpose of developing a manufacturing alternative that uses lighter materials and has less environmental impact. Theoretical Framework: The study is based on the principles of forging at different temperature combinations, exploring the interaction between an element manufactured by a relatively recent additive manufacturing technology, in order to improve the process. Aspects such as metallography of the elements, characterization of the deposited material and analysis of the union between the two materials were considered to better understand the variables involved in production. Method: The methodology adopted for this research involves exploratory research seeking to deepen knowledge about the production of bimetallic elements, using metallographies of the constituents present in this union. Eight test pieces and appropriate tooling were developed in order to develop the samples. Results and Discussion: The results obtained revealed localized cracks in some samples, possibly caused by uneven contraction during cooling of the materials. The temperature of the steel promoted few microstructures near the bimetallic boundary. The temperature of 550 ºC for forging the deposited steel and aluminum at room temperature should be reviewed due to the difference in contraction during cooling after warm forging. The union between the two metals occurred basically by mechanical locking, which occurred during forging. Research Implications: The results of this work demonstrate the applicability of replacing traditional mechanical elements with the manufacture of forged bimetallic components. Furthermore, the research raises an issue regarding the reduction of pollutant emissions, sustainability and competitiveness in various segments of the industry. Originality/Value: This study contributes to the literature by presenting an efficient alternative for the production of parts by additive manufacturing, integrated with another material through forging. This approach favors the reduction of costs, fuel consumption and environmental impacts in different sectors of the industry. The relevance of the research is evident in the combination of additive manufacturing with the forging of bimetallic elements, bringing significant benefits to the automotive industry — both combustion and electric vehicles —, aerospace and other industrial segments.