Influence of the structure and asymmetry of loading cycles on the cyclic crack resistance of Ti-Si composites
No author None.
We analyze fatigue-crack growth rate diagrams for various modifications of a Ti-Si cermet alloy in the initial (as-cast) state and after thermomechanical treatment plotted for beam specimens subjected to three-point bending. It is shown that, for different asymmetries of the loading cycle, the maximum stress intensity factor K max better describes the behavior of the growth rate of fatigue macrocracks in the high-amplitude part of the diagrams than the range of the stress intensity factor ΔK. The threshold crack resistance of the Ti-Si composite under cyclic loading is 2-5 times lower than under long-term static loading. For highly asymmetric loading cycles (R = 0.6), the maximum cyclic crack-growth resistance is exhibited by a modification with the structure of grains of pseudo-α-titanium matrix 20-40μm in size and 15-30wt.% of dispersed precipitations of titanium and intermetallic silicides 5-10μm in size.