Fracture toughness and fatigue crack growth analysis of 7050-T7451 alloy thick plate with different thicknesses

WANG Yi-lin(王艺淋)¹, PAN Qing-lin(潘清林)^{1, 2}, WEI Li-li(韦莉莉)¹, LI Bo(李波)¹, WANG Ying(王迎)¹

(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Materials Science and Engineering of Ministry of Education
(Central South University), Changsha 410083, China)

Abstract:The strength, fracture toughness and fatigue crack growth resistance of 7050-T7451 aluminum alloy plate with different thicknesses (35 mm and 160 mm) were investigated by means of optical microscope, scanning electron microscope and transmission electron microscope. The results show that thicker plate has lower strength and fracture toughness but higher fatigue crack growth resistance, by comparison to the thinner plate. The drop of strength is mainly attributed to grain coarsening in the thicker plate, and the increased degree of recrystallization results in the loss of K_IC. However, the coarsened grains in the thicker plate make cracks deflected and closure effect enhanced due to surface roughness increased. For both of plates, in the fracture surface subjected plain strain, a transition from transgranular dimpled fracture to intergranular dimpled fracture is observed during the fracture process.

Key words:7050-T7451 plate; strength; fracture toughness; fatigue crack growth