Mechanical anisotropy and fracture behaviour of bulk ultra-fine grained AA2099 alloy

ABSTRACT

In this work, the effect of cryo-deformation and post-deformation annealing process on tensile, anisotropic and fracture behaviour of AA2099 has been investigated. The development of ultrafine-grained (UFG) microstructure is achieved initially by cryorolling (CR) process on the solution-treated (ST) alloy by subjecting it to a true strain value of 2.3. Cryorolled samples are then followed by annealing process at temperatures of 150°C (CR + 150°C) and 200°C (CR + 200°C). A notable improvement in yield strength (~342 MPa), ultimate tensile strength (~472 MPa), hardness (~138 HV) and fracture toughness parameters (K_Q (31.8 MPa$\surd \mathit{m}$), K_ee (31 MPa$\surd \mathit{m}$) and J integral (57.67 kJ/m²)) is recorded, whereas anisotropy increases in the rolling direction and ductility show a significant drop at CR sample condition in comparison with coarse grains at ST condition. When annealing was executed at 150°C and 200°C, notable improvements in tensile, anisotropic and fracture behaviour of UFG AA2099 were observed. There has been a significant enhancement in tensile strength, anisotropy and fracture toughness until temperature reaches 150°C being the highest (~506 MPa), whereas after 150°C, these properties have been shown to decrease notably.

KEYWORDS:

• Ultrafine grains (UFG)
• mechanical anisotropy
• fracture toughness

Disclosure statement

No potential conflict of interest was reported by the authors.