Effect of a Heterogeneous Nitrogen Diffusion Phase on Four-Point Bending Fatigue Properties in Commercially Pure Titanium

Abstract

The purpose of this study is to develop commercially pure (CP) titanium having a higher fatigue strength than titanium alloys developed via heterogeneous nitrogen diffusion. The microstructure of CP titanium having a heterogeneous nitrogen diffusion phase, which was fabricated by consolidating gas-nitrided powders, was characterized, and its fatigue properties were examined. The nitrogen content and hardness of CP titanium compacts having a heterogeneous nitrogen diffusion phase increased with increasing powder gas nitriding temperature and sintering temperature. The fatigue limit and fatigue life of CP titanium compacts increased with increasing sintering temperature and with decreasing powder gas-nitriding temperature. In particular, CP titanium having a heterogeneous nitrogen diffusion phase that is fabricated by hightemperature sintering of powders treated with low-temperature nitriding has a higher fatigue limit than un-nitrided bulk Ti6Al4V alloy. The fatigue limit of CP titanium can be controlled by optimizing the powder gas nitriding and sintering temperatures.

In situ observation of fatigue crack propagation in soda‐lime glass with initial crack and residual stress induced by Vickers indentation under four‐point bending

“…The specimen surface cannot be directly observed under four‐point bending. We thus previously proposed a system for the in situ observation of fatigue cracks 30,33–36 . Figure 4 shows a schematic diagram of this system.…”

“…We thus previously proposed a system for the in situ observation of fatigue cracks. 30,[33][34][35][36] Figure 4 shows a schematic diagram of this system. In this system, a reflector is installed on the fatigue test jig to enable the observation of the surface subjected to tensile stress to observe fatigue crack propagation using an optical microscope under static or cyclic loading.…”