Structure and Mechanical Properties of Al Thin Films Synthesized by Electron Beam Evaporation and Ion Beam Assisted Deposition
C E. Kalnas, David T. Read, J E. Jones, G S. Was
The effects of an Ar ion assist beam during Al film growth by electron beam evaporation on the film composition, microstructure, and texture were assessed in addition to the mechanical properties of hardness, elastic modulus, yield strength, ultimate tensile strength and ductility. Al films with a target thickness of 500 nm were synthesized by electron beam evaporation (EBE) and ion beam assisted deposition (IBAD) at a nomalized energy input of 40 eV/atom. All films contained equivilent levels of O impurities (1-2 at. %) and exhibited a (111) fiber texture. IBAD Al had a 25% higher volume fraction ratio of 111 to randomly oriented grains. Grain refinement was observed in the IBAD Al film; the mean planar grain size of IBAD Al was 120 nm compared to the mean planar grain size of 260 nm for EBE Al. Free-standing film tensile tests showed that the 0.2% offset yield strengths of both films were strengths from the nanoindentation hardness effects during the indentation process. Higher levels of work-hardening in IBAD Al compared to EBE Al are observed on the stress-strain curves. Increased work-hardness, due to irradiation defects in IBAD factor of 2 higher ductility thatn IBAD Al films. Fracture morphologies of the tensile specimens were distinctly different; EBE Al tensile specimens failed by necking to a point, while the IBAD Al exhinited intergranular fracture. It is likely that the reduced ductility and intergranular fracture in IBAD Al is due to irradiation defects. Film elestic module calculations from the composite (film+substrate) nanoindentation data were reasonable for EBE Al (71-93 Gpa), but not for IBAD Al (28-53 Gpa). This may be due to the effects of Ar incorporation in IBAD Al.
aluminum, ion bombardment, mechanical properties, microstructure
, Read, D.
, Jones, J.
and Was, G.
Structure and Mechanical Properties of Al Thin Films Synthesized by Electron Beam Evaporation and Ion Beam Assisted Deposition, Thin Solid Films, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851192
(Accessed May 28, 2023)