Issue34

A. Tajiri et alii, Frattura ed Integrità Strutturale, 34 (2015) 347-354; DOI: 10.3221/IGF-ESIS.34.38 352 specimen, indicating that the texture evolution is weaker under lower strain rate. Consequently, it could be concluded that H specimen has stronger texture. As shown in Fig.3, H specimen exhibited lower fatigue strengths than L specimen due to lower crack growth resistance (Fig.6). The lower resistance could be attributed to the stronger texture induced by FSP under higher strain rate. It is concluded that the elimination of casting defects is mandatory to improve fatigue strength of the as-received cast Al alloy, and in addition, FSP condition with weaker texture could give further increase of fatigue strength. Figure 8 : EBSD analysis results along crack path in L specimen: (a) Fatigue crack growth path, (b) Pole figures at the rectangular regions in (a). C ONCLUSION SP was applied to T6-treated A356 Al alloy under two different FSP conditions with low and high tool rotational speeds. The plane bending fatigue tests were conducted to investigate the effect of FSP conditions on fatigue properties. EBSD analyses were performed to figure out the texture evolution. The conclusions are as follows. (1) Casting defects were successfully removed by both FSP conditions. Clear onion ring patterns were fully developed under high tool rotational speed, while onion rings were partially formed near the top of the probe under low speed. (2) The fatigue strengths of FSP specimens were improved compared to the as-cast specimen, due to the elimination of casting defects. FSP under lower tool rotational speed could further improve fatigue strength than the higher speed. (3) L specimens exhibited higher crack initiation and growth resistances than H specimen. The higher resistances could be attributed to the weaker texture evolution under lower strain rate. F Figure of fcc unit cell {001} pole figure {111} pole figure {110} pole figure Region in Fig.18(a) (A) (B) (C) (D) (E) (F) ND TD RD (A) (B) (C) (D) (E) (F) 1mm R-side A-side (a) (b)