P-Texture Effect on the Fatigue Crack Propagation Resistance in an Al-Cu-Mg Alloy Bearing a Small Amount of Silver

• Main Authors: Yangcheng Hu, Zhiyi Liu, Qi Zhao, Song Bai, Fei Liu
• Format: Article
• Language: English
• Published: MDPI AG 2018-12-01
• Series: Materials
• Subjects: Al-Cu-Mg-Ag alloy; P-texture; roughness induced crack closure; fatigue crack propagation resistance; damage tolerance
• Online Access: https://www.mdpi.com/1996-1944/11/12/2481

P-texture effect on the fatigue crack propagation (FCP) resistance in an Al-Cu-Mg alloy containing a small amount of Ag, is investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back scattering diffraction (EBSD). Results shows that the high intensity P-texture sheet has lower <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi mathvariant="sans-serif">&#963;</mi> <mrow> <mn>0.2</mn> </mrow> </msub> <mo>/</mo> <msub> <mi mathvariant="sans-serif">&#963;</mi> <mi>b</mi> </msub> </mrow> </semantics> </math> </inline-formula>, lower FCP rate and higher damage tolerance than random texture sheet. Fracture analysis indicates that the striations spacing of high intensity P-texture sheet is much smaller than that of random texture sheet and it has a rougher fatigue fracture surface, which causes a significant roughness induced crack closure (RICC) effect. The calculation results manifest that high intensity P-texture sheet possesses a higher crack closure level reaching 0.73 as compared to random texture sheet (only 0.25). The statistical analysis results reveal the P-grains have large twist angle of 105&#8315;170&#176; and tilt angle of 5&#8315;60&#176; with neighboring grains, which is similar to Goss-grains. This is the fundamental reason that P-texture sheet has the same FCP resistance and induces fatigue crack deflection as Goss-texture sheet. Additionally, the most {111} slipping planes of P-grains are distributed in the range of 30&#8315;50&#176; deviating from transverse direction of the sheet. This results in more {111} slipping planes to participate in cyclic plastic deformation, which is beneficial to reduce fatigue damage accumulation and improve the damage tolerance of Al-Cu-Mg-Ag alloy.