TC4 (Ti-6Al-4V) is a comprehensive metal material with excellent ductility, low density, high specific strength, and a series of advantages such as excellent toughness and weldability, so it is widely used in the aerospace industry. Due to defects such as porosity in the welding process and exposure to alternating loads, welded components of titanium alloys in the aerospace industry become the most vulnerable parts and are extremely susceptible to failure and fracture. In this paper, a single-sided sequential laser impact strengthening process is used to treating the laser welds of TC4 titanium alloy cold rolled parts to investigating the tensile properties of the laser welded welds before and after the process. By observing the tensile fracture by SEM, measuring the microhardness by Vickers hardness tester, and measuring the physical phase by XRD diffractometer, the results of these data were combined to analyze the strengthening mechanism of this laser shock peening process on the laser welds of TC4 titanium alloy. The experimental results show that after the surface strengthening process, the tensile strength and surface hardness of TC4 laser welds are improved compared with those before 1the treatment. The analysis shows that the high residual compressive stress layer and grain refinement caused by laser shock peening are the reasons for the improvement of mechanical properties of materials.
Laser shock peening without protective coating leads to mechanical and thermal loads of materials, resulting in surface melting and re-solidification. In this paper, the effect of laser shock peening (LSP) with and without protective coating on the surface behavior of AZ31B magnesium alloy was studied. Study on surface mechanical property of magnesium alloy by different LSP process parameters. The effects of different LSP parameters on the surface properties of the sample were studied by microhardness test, phase analysis, et al. The results show that the increase of laser power density, the surface hardness of the sample increases. Compared with the LSP with protective coating, the LSP without protective coating increases the surface roughness. And resulting microstructure and residual stress state were studied, After LSP treatment, diffraction peaks shift to high angle direction, resulting in residual compressive stress on the surface of the material.
Ti-6Al-4V (TC4) titanium alloys have been extensively used in aviation due to their good comprehensive mechanical properties. However, TC4 has low hardness and poor wear resistance, which cannot meet the increasingly stringent working environment requirements of aerospace. Thus, it is necessary to enhance their performance by posttreatment. Laser shock peening (LSP) is an advanced surface treatment technology that improve the hardness and fatigue life of the metal material by ultra-high plastic strain. However, laser shock peening has limits to improve the surface hardness of workpiece. And heat treatment can effectively improve the performance of titanium alloys. Therefore, the combination of heat treatment and laser shock peening is used to improve the surface hardness of TC4. In this study, the Ti-6Al-4V (TC4) samples were subjected to one and two LSP impacts, respectively. Heat treatment was performed on the sample that has been subjected to one impact, and one of the heat-treated samples was subjected to one impact again. The surface hardness was measured by a Vickers hardness tester meter. The fracture morphologies were observed by scanning electron microscope (SEM) and phase characterization was measured by X-ray diffractometer (XRD). The effect of laser shock peening and heat treatment on the surface hardness of TC4 samples was experimentally investigated. The results showed that the maximum surface hardness of the treated sample was increased by 56.8% compared with original sample. Therefore, the combination of laser shock peening and heat treatment can greatly increase the surface hardness of the TC4.
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