报告人：Prof. Tongguang Zhai （Department of Chemical and Materials Engineering, University of Kentucky，USA）

报告时间：2015年7月9日上午10:00

报告地点：物理学院201多功能会议室

报告简介：The talk will begin with a brief review on our recent research activities including: 1) anomalous strain rate effect on ductility in Mo-Re alloys; 2) formation mechanism of an unusual texture in Al alloys; 3) formation mechanism of the high-temperature precipitation in 6000 Al alloys; and 4) 3-D effects of microstructure on fatigue crack initiation in engineering alloys, etc. The talk will then be focused on a microstructure-based model that has recently been developed to quantify short fatigue crack growth in 3 dimensions in planar slip alloys, such as high strength Al alloys and Ni-base superalloys, etc. The model takes into account both the local driving force and resistance in calculating short crack growth. The resistance of a gran boundary to short fatigue crack growth was characterized to be as a Weibull-type function of the twist angle of the crack plane deflection at the boundary, using an experimental technique newly developed in the author’s lab. The total resistance at a grain boundary is also contributed by all its neighboring grain boundaries as a normal distribution function of distance. The driving force for crack growth is the ΔK at the furthest point along the crack. The effective driving force is then this driving force minus the total resistance at each grain boundary along the crack front, and used in the modified Paris equation to quantify the growth behavior of the crack in 3 dimensions. This model has been verified by the surface growth rate of a short crack, measured experimentally, in an Al-Li alloy. The model could incorporate the effects of grain structure and texture in simulating the short fatigue crack growth. It shows that texture could significantly affect the life of a short fatigue crack. This model presents the potentials for more accurate prediction of the life of an engineering alloy and advancement of alloy design technology.

邀请人：吴奕初教授