Study On The Mechanism Of YAG-ZrO₂ Fiber Fluorescence Spectroscopy To Stress-strain Of Aluminum Matrix Composites

It has important practical significance for the internal stress detection and fatigue prediction of equipment components,but it is difficult to detect the internal stress in real time without damaging the material.Using rare earth fluorescence performance to detect stress is a feasible method.Its advantage is that the fluorescence spectrum of rare earth ions is rich,sharp and easy to find peaks,and most of them are highly sensitive to stress.In this study,Tb³⁺and Eu³⁺were selected as the luminescent center,the Tb³⁺and Eu³⁺doped YAG-ZrO₂composite fibers(abbreviated as(YAG:Tb³⁺-ZrO₂)_cfand(YAG:Eu³⁺-ZrO₂)_cf)were prepared with different concentrations of Tb³⁺and Eu³⁺using electrospinning technology.The fibers have the fluorescence properties of rare earth.The optimal doping concentration was obtained.The YAG-ZrO₂composite fiber is compounded with 2024 aluminum alloy(referred to as(YAG-ZrO₂)_cf/Al composite material)using hot-press sintering technology,the(YAG-ZrO₂)_cf/Al composite material has rare-earth fluorescence properties while being enhanced.The effect of different fiber additions on the mechanical properties of composite materials was studied,the optimal fiber doping amount was determined,and the stress sensor was obtained by analyzing the fluorescence properties of the material and the external stress of the(YAG-ZrO₂)_cf/Al composite material.The response mechanism of the fluorescence features to the stress sensing was analyzed.Through the in-situ tensile XRD experiment,the law between the internal stress and the external stress of the(YAG-ZrO₂)_cf/Al composite material in the stretching process was obtained,and the combination with the stress sensing equation completes the detection of the internal stress in the material.The main research contents were as follows:(1)The(YAG:Tb³⁺/Eu³⁺-ZrO₂)_cfwith different doping concentrations of Tb³⁺and Eu³⁺was prepared by electrospinning,the structure,morphology and optical properties of the fiber were studied.Studies have found that the fiber has good crystallinity,Tb³⁺doped into the lattice of the matrix,and Eu³⁺occupies the Y³⁺lattice site.The fiber surface was smooth.The diameter was about 250 nm,the length was about 20?m,and the fiber has excellent optical properties.The optimal doping amount of Tb³⁺was 6 mol%,and the optimal doping amount of Eu³⁺was 4 mol%.Excited by an ultraviolet light source(YAG:Tb³⁺-ZrO₂)_cfcan emit green light with a wavelength around 544 nm,and(YAG:Eu³⁺-ZrO₂)_cfcan emit orange-red light with a wavelength around 592 nm.(2)The study found that adding a small amount of(YAG-ZrO₂)_cfto the aluminum alloy can improve the mechanical properties of the material.When the fiber addition amount was 2 wt.%,the density and hardness reach the maximum of 98.3%and 123.8HV,respectively.When the fiber content is 2 wt%,the tensile strength and elongation of the composites increase by 14%and 46%.When the amount of fiber doping increases,it will reduce the mechanical properties of the material.Through PL spectroscopy,the composite material will also emit light of a specific wavelength when excited by the excitation light source.This function provides the possibility for the subsequent detection of the internal stress of the composite material through the rare-earth fluorescence spectroscopy effect.(3)The relationship between the emission spectra of(YAG:Tb³⁺/Eu³⁺-ZrO₂)_cf/Al composite material and tensile stress was studied.By analyzing the integrated intensity value and the wavelength of the center of gravity,it was found that the wavelength of the center of gravity of the(YAG:Eu³⁺-ZrO₂)_cf/Al composite exhibits higher tensile stress sensing accuracy.The sensing equation was?=594.90616+0.01439?,and the sensitivity was 0.01439 nm/MPa(equivalent to a frequency shift coefficient of 0.4058 cm^-1/MPa).Compared with the frequency shift coefficient(0.0055 cm^-1/MPa)of the standard fluorescence spectroscopy material ruby,the sensitivity was increased by about 80 times.(4)By analyzing the XRD pattern of the(YAG-ZrO₂)_cf/Al composite material during the in-situ stretching process,the internal stress of the material changes with the tensile stress,and the law equation is y=381.10723+0.15676?.According to the existing research,it is shown that a small amount of rare earth ion doping YAG-based fiber will not change the fiber's reinforcement performance,so this law equation can be applied to(YAG:Eu³⁺-ZrO₂)_cf/Al composite materials.Combining the law equation with the gravity center wavelength sensing equation of(YAG:Eu³⁺-ZrO₂)_cf/Al composite material?=594.90616+0.01439?can get the internal stress detection equation y=10.894?-6099.583.According to this equation,the fluorescence properties of the material can be used to detect the internal stress of the material during the stretching process.