Characteristics of aluminium–scandium alloy thin sheets obtained by physical vapour deposition

Thin sheets of an age-hardenable aluminium–scandium alloy were deposited by direct current magnetron sputtering. As targets an aluminium–scandium pre-alloy with a scandium content of 2.0 mass% (size 88 × 500 mm) was applied. The substrates to be coated consisted of thin steel sheets which after deposition were dissolved in an oxidizing medium. In this way, free-standing sheets of less than 30 μm thickness of the aluminium–scandium alloy were received. Two deposition temperatures, 37 and 160 °C, were applied. The as-received sheets showed a typical columnar structure. Two post-treatments of the sheets were applied: a cold isostatic pressing and an artificial ageing for 1 h at temperatures between 200 and 400 °C. The strength of the sheets was measured by tensile tests. The employed specimens had a width of 10 mm and were gained from the sheets by cutting. During testing, load and strain were measured by a 1000 N load cell and a video extensometer, respectively. The as-deposited specimens show a tensile strength of 350 MPa. Artificial ageing at 300 °C increases the tensile strength to more than 400 MPa. It could be shown that during tensile tests cracks are initialized at coating defects.