Tensile properties and drawability of thin bimetallic aluminum-scandium-zirconium / stainless steel foils and monometallic Al-Sc-Zr fabricated by magnetron sputtering

Julien Kovac,Lukas Heinrich,Bernd Koehler,B Clausen ,A Mehner ,H.‐W Zoch

doi:10.1051/matecconf/201819015001

Abstract

Al-Sc-Zr alloys are interesting for the production of high strength micro components by micro deep drawing. These alloys show a good hardenability due to the formation of nanometer-scale spheroidal Al3(Sc, Zr) precipitates, which are highly coherent with the aluminum matrix. However, the formation of these precipitates in Al-Sc-Zr foils fabricated by conventional metallurgical methods dramatically reduces their ductility and drawability. In this work, magnetron sputtering was used to produce Al-Sc-Zr foils and Al-Sc-Zr / stainless steel bimetallic foils which are nearly free of these precipitates. Tensile tests were carried out to measure and compare the mechanical properties of monometallic Al-Sc-Zr foils and bimetallic Al-Sc-Zr / stainless steel foils deposited with varying plasma target powers and containing different volume fractions (layer thickness) of Al-Sc-Zr. Micro deep drawing was used to determine the drawability of selected monometallic and bimetallic foils. The results show that the density of monometallic Al-Sc-Zr foils can be improved significantly by increasing the DC target power and by using the high power impulse magnetron sputtering (HiPIMS) technology, resulting in foils with higher ductility. Bimetallic foils achieved higher strength and ductility than monometallic Al-Sc-Zr foils. Their mechanical properties vary with the target power and the volume fraction (thickness) of Al-Sc-Zr. The limit drawing ratio of HiPIMS deposited monometallic foil was 1.7 or 1.8 depending on the side of the foil facing the die, whereas a limit drawing ratio of 1.9 was observed for bimetallic foils.

Highlights

Micro deep drawing is an efficient cold sheet forming process for the mass production of hollow microscopic parts with complex shape, which are widely used in micro system technologies (MST) and micro electromechanical systems (MEMS) such as connector pins, resistor caps, lead chip frames or parts of pressure sensors [1]
The principle of micro deep drawing is essentially similar to the conventional deep drawing process: a metallic sheet is maintained by a blank holder and put in shape through the action of a punch into a die
The foil produced at 4 kW (MDC4) and the high power impulse magnetron sputtering (HiPIMS) deposited foil (MHP) are overall denser since porosities are less frequent and confined to the near free surface region

Summary

Introduction

Micro deep drawing is an efficient cold sheet forming process for the mass production of hollow microscopic parts with complex shape, which are widely used in micro system technologies (MST) and micro electromechanical systems (MEMS) such as connector pins, resistor caps, lead chip frames or parts of pressure sensors [1]. The microscopic dimensions of the finished parts require the use of thin foils with a thickness generally below 50 μm instead of sheets of a few millimeters thickness. This thickness reduction leads to the occurrence of size effects which greatly influence the mechanical and tribological behavior of the drawn foil [2].

Methods

Results

Conclusion