Abstract
In addition to AZ- and AM-series magnesium alloys, which are mainly used at ambient temperature, there are also die-cast magnesium alloys developed for use at elevated temperatures. This paper examines the compressive creep resistance of several aluminium-containing magnesium high-pressure die-cast alloys, including the commercially available AE42, AE44-2, AE44-4, MRI230D alloys and newly developed DieMag series, i.e. DieMag211, DieMag422 and DieMag633. Compressive creep is the common load case for automotive powertrain components such as transmission housings, engine blocks or oil pans, which are typically mounted with steel or aluminium bolts that have lower thermal expansion than magnesium alloys. When the components heat up, there is a compressive load in the area around the bolt. The compressive creep experiments are accompanied by microstructure investigations. It is shown that MRI230D and the two high-concentrated DieMag alloys have the best creep resistance at 200°C. Similar results are also observed in the tensile tests at room temperature and 150°C, with DieMag633 showing outstanding strength.
Highlights
Magnesium alloys are predominantly cast (Avedesian and Baker, 1999)
From the dumb-bell samples, cylinders with a diameter of 6 mm and a length of 15 mm for compressive creep testing were produced by electric discharge machining
The compressive creep tests were performed at a constant temperature of 200◦C and constant stresses of 60, 70, 80, 90, and 100 MPa using an ATS Lever Arm Creep Machine
Summary
Magnesium alloys are predominantly cast (Avedesian and Baker, 1999). Only a small proportion of the alloys used are formed, e.g., rolled, extruded, or forged. These commercial alloys are compared with DieMag alloys, which have an aluminum-barium-calcium proportion of 2:1:1 They differ only in the absolute content of alloying elements and were produced under the same conditions and casting parameters via HPDC (Dieringa et al, 2013). Gearbox housings, pump housings, motor blocks, oil pans, or similar temperature-loaded components are manufactured from the alloys investigated These components are under compressive stress in the areas where they are bolted together. In this paper the compressive creep resistance of all alloys at 200◦C and different stresses between 60 and 100 MPa shall be investigated These are approximately the maximum temperatures and stresses that outer areas of an engine block must withstand under a bolt load. The creep tests are accompanied by optical and electron microscopy in combination with an investigation of intermetallic phases to elucidate the mechanism of deformation
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