Lateral Angular Co-Extrusion: Geometrical and Mechanical Properties of Compound Profiles

Abstract

A novel co-extrusion process for the production of coaxially reinforced hollow profiles has been developed. Using this process, hybrid hollow profiles made of the aluminum alloy EN AW-6082 and the case-hardening steel 20MnCr5 (AISI 5120) were produced, which can be forged into hybrid bearing bushings by subsequent die forging. For the purpose of co-extrusion, a modular tooling concept was developed where steel tubes made of 20MnCr5 are fed laterally into the tool. This LACE (lateral angular co-extrusion) process allows for a variation of the volume fraction of the reinforcement by using steel tubes with different wall thicknesses, which enabled the production of compound profiles having reinforcement contents of either 14 vol.% or 34 vol.%. The shear strength of the bonding area of these samples was determined in push-out tests. Additionally, mechanical testing of segments of the hybrid profiles using shear compression tests was employed to provide information about the influence of different bonding mechanisms on the strength of the composite zone.

Challenges in the Forging of Steel-Aluminum Bearing Bushings

“…The workpieces were fabricated by machining, fitted together with a tolerance H7/g6 for a diameter of 44 mm (clearance fit) without metallurgical bonding, and subsequently formed to the final geometry. The steel thickness investigated in this work was chosen by analogy with the coextrusion process, which produces hybrid workpieces with initial bonds for further investigation, in order to be able to make a comparison [ 20 ].…”

Process chain for the manufacture of hybrid bearing bushings

“…• Conventional billets: This variant is based on the use of mono-material billets without reinforcement, as these are Fig. 1 Schematic Tailored Forming process chain for the demonstrator component of the hybrid bearing bushing, starting with a Lateral Angular Co-Extrusion (LACE) process for the manufacture of the bi-metal semi-finished products and subsequent forming into the aluminum/steel bulk metal component by die forging; according to [5] commonly used in industrial extrusion approaches. The reinforcing element is thus, introduced into the forming zone from the outside and, unlike the matrix material, not deformed plastically [11].…”

“…Recent investigations by Thürer et al employing a new tool design at near-industrial scale as well as 20MnCr5 steel tubes as reinforcing elements have already shown that sufficiently coaxial aluminum-steel hollow profiles featuring reinforcement contents of both 14 vol% and 34 vol% can be successfully achieved. In addition, shear strengths of up to 58 MPa ± 15 MPa were determined on sample segments that included the joining zone, which indicated the presence of a metallurgical bond by adhesion of aluminum to the steel [5]. For the planned subsequent die forging step within the Tailored Forming process chain (compare schematic process chain in Fig.…”

“…Since the LACE process is used to encase a rigid reinforcement with a light metal, a mandrel component was designed, which is held in the tool by three support arms, arranged at an angle of 120° to each other. The procedure for this specific LACE process has been described recently by Thürer et al [5] and Fig. 2b shows four steps of the simulated material flow of the aluminum.…”

A design concept of active cooling for tailored forming workpieces during induction heating

“…The required materials are joined to hollow steel-aluminium profiles by a co-extrusion process. After the joining, there is a metallurgical bond without intermetallic phase in the interface zone [23]. The presented work considers a strategy for setting the required temperature gradient in the above-described workpieces before the forging process.…”