PSI - Issue 25

Francesco Leoni et al. / Procedia Structural Integrity 25 (2020) 348–354 Francesco Leoni / Structural Integrity Procedia 00 (2019) 000–000

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1. Introduction In recent years automotive and product supplying industries have increased their use of aluminum because of its cost efficiency and excellent recyclability. Al-Mg-Si alloys are widely used in the transport field thanks to their high specific strength. However, the exposure to high temperatures can drastically decrease the mechanical strength of such heat treatable Al-Mg-Si alloys. This behavior is due to the deterioration of the microstructure of the alloy. Alloying elements such magnesium and silicon are often added to improve the alloy strength at room temperature as well as at higher temperatures Mohamed, Samuel and Al Kahtani (2013). When the alloy is subjected to temperatures above 190 °C, the major alloy strengthening phases which include the β’’ phase will tend to become unstable, coarse rapidly and then dissolve. A better understanding of the behavior of the mechanical performance of the alloy at different temperatures is crucial in the design of components that are exposed to a wide range of temperatures. In addition, the advanced use of mathematical models and finite element (FE) codes can be of great help. Modeling of such behavior can be done by calibrating parameters of constitutive equations by analyzing experimental data by which the flow stress associated with the viscoplastic deformation is related to the viscoplastic strain rate and temperature Gouttebroze, Mo, Grong, Pedersen and Fjær (2008). Recently, analysis of the behavior of a new solid-state joining process known as the Hybrid Metal Extrusion & Bonding (HYB) process has been carried out Grong (2012); Grong, Sandnes and Berto (2019); Sandnes et al. (2018). Until now, the development has been done using a combination of 3D computer-aided design (CAD), rapid prototyping and laboratory testing, in accordance with well-established design methodology Ulrich and Eppinger (2008). Therefore, the next natural step in the HYB process development would be to optimize the performance of the extruder through finite element (FE) modelling of the filler wire feeding. The HYB method utilizes continuous extrusion as a technique to enable filler metal additions. This metal addition is done by feeding a filler wire with a diameter of 1.4 mm into the specially-designed HYB PinPoint extruder. The wire feeding in the HYB process is a crucial part of the whole joining operation. In a previous paper by the authors, the commercial software package Deform 3D TM has been successfully employed in modeling the material flow pattern inside the HYB PinPoint extruder using the default flow stress data provided by the software material library Leoni, Sandnes, Grong and Berto (2019). To upgrade the material properties used as input to the simulations, a series of dedicated tensile test experiments have been carried out in steps from room temperature (RT) and up to 500 °C employing the 1.4 mm diameter AA6082 wire. This covers the entire temperature range being typical of the extrusion process. 2. Materials and methods The 1.4 mm diameter filler wire tested is of the AA6082 type. The wire chemical composition is shown in Table 1.

Table 1: Nominal chemical composition of the AA6082 filler wire (in wt %).

Al

Si

Mg

Mn

Fe

Cr

Cu

Ti

B

Zr

Other 0.029

Balance 1.11

0.61

0.51

0.20

0.14

0.002

0.043

0.006

0.13

The filler wire manufacturing route is illustrated in Figure 1.

Figure 1: Schematic drawing showing the filler wire manufacturing route.