Tailored Forming of hybrid bulk metal components

Abstract

Multi-material bulk metal components allow for a resource efficient and functionally structured component design, with a load adaptation achieved in certain functional areas by using similar and dissimilar material combinations. One possibility for the production of hybrid bulk metal components is Tailored Forming, in which pre-joined semi-finished products are hot-formed using novel process chains. By means of Tailored Forming, the properties of the joining zone are geometrically and thermomechanically influenced during the forming process. Based on this motivation, forming processes (die forging, impact extrusion) coupled with adapted inductive heating strategies were designed using numerical simulations and successfully realised in the following work in order to produce demonstrator components with serial or coaxial material arrangements. The quality of the joining zone was investigated through metallographic and SEM imaging, tensile tests and life cycle tests. By selecting suitable materials, it was possible to achieve weight savings of 22% for a pinion shaft and up to 40% for a bearing bush in the material combination of steel and aluminium with sufficient strength for the respective application. It was shown that the intermetallic phases formed after friction welding barely grow during the forming process. By adjusting the heat treatment of the aluminium, the growth of the IMP can also be reduced in this process step. Furthermore, for steel-steel components alloy savings of up to 51% with regard to chromium could be achieved when using low-alloy steel as a substitute for high-alloy steel parts in less loaded sections. The welded microstructure of a cladded bearing washer could be transformed into a homogeneous fine-grained microstructure by forming. The lifetime of tailored formed washers nearly reached those of high-alloyed mono-material components.

Investigation of the joining zone formation of impact extruded hybrid components by varied forming sequence and partial cooling

“…Based on the concept of the studies mentioned, the new approach called Tailored Forming enables a production of load-adapted high-performance components by forming pre-joined hybrid semi-finished products. The process chain can differ in terms of joining processes used such as friction welding, lateral angular co-extrusion (LACE) or cladding and subsequent forming processes such as impact extrusion or die forging [10].…”

“…This is followed by machining to produce the final component, which is characterised by a load-adapted material distribution. The process chain of Tailored Forming has already been used in earlier work to create customised, hybrid machine parts in serial and coaxial arrangements like axial bearing washers or bevel gears [10]. The parameters were chosen according to the previous work [18] and are designed to prevent unnecessary shortening and to set low temperatures in order to keep the emerging intermetallic phase as small as possible.…”