Titanium alloy composition determination method and system based on spectrometer

Abstract

The application discloses a titanium alloy component determination method and system based on a spectrometer, and comprises the following steps: focusing a first laser pulse on the surface of a titanium alloy sample to be measured to generate an initial excitation area; after a preset delay time after the action of the first laser pulse, a second laser pulse is applied to the initial excitation area; during the action of the second laser pulse, the spectrum signal emitted by the initial excitation area is collected in at least two different preset polarization analysis directions to obtain polarization-resolved spectrum data; a characteristic analysis signal of a target element is obtained; and the component content of each element in the titanium alloy sample to be measured is calculated according to the characteristic analysis signals of the target elements. The spectrum signal is collected in at least two different preset polarization analysis directions to obtain polarization-resolved spectrum data, and the response signal under a specific polarization direction combination is calculated to obtain a characteristic analysis signal, so that the isotropic background radiation and the spectral line interference of non-target elements are effectively suppressed from the physical principle.

Description

Technical Field

[0001] This invention relates to the field of materials composition analysis technology, specifically to a method and system for determining the composition of titanium alloys based on a spectrometer. Background Technology

[0002] Titanium alloys, with their excellent specific strength, corrosion resistance, high temperature resistance and good biocompatibility, have become the core material for key rotating components of aerospace engines, main load-bearing structures of spacecraft, biomedical implants and high-end chemical equipment.

[0003] Laser-induced breakdown spectroscopy (LIBS) is a promising atomic emission spectroscopic analysis technique. It focuses a high-energy laser pulse onto the sample surface, causing trace amounts of material to vaporize instantaneously and form a high-temperature plasma. By analyzing the elemental characteristic spectra emitted by this plasma during the cooling process, qualitative and quantitative analysis of the sample elements can be achieved. LIBS technology has attracted widespread attention in the field of materials analysis due to its outstanding advantages, such as requiring no complex sample pretreatment and being able to perform micro-area, in-situ, remote, and even elemental distribution imaging analysis.

[0004] However, when applying LIBS technology to the composition verification and quality screening of the aforementioned high-value-added titanium alloy products (such as precision-machined engine blades and surface-treated implants), some problems still exist. For example, the analysis basis of traditional LIBS technology relies on the ablation of the sample by a laser to generate plasma. This process inevitably forms micron-scale ablation pits on the sample surface, causing permanent physical damage. For components with extremely high value, extremely stringent structural integrity requirements, and where no defects that may become fatigue crack sources are allowed, such destructive testing methods are unacceptable. Although the damage can be reduced by lowering the laser energy, it will directly lead to a sharp deterioration in signal intensity and signal-to-noise ratio, thus losing the value of quantitative analysis.

[0005] Furthermore, titanium alloys are not pure metals; their properties are controlled by adding various elements such as aluminum, vanadium, iron, molybdenum, and chromium. The characteristic emission lines of these elements are densely distributed on the spectrum, and due to the inherent broadening effect of laser plasma, the spectral line width increases, leading to severe overlap and interference between the spectral lines of different elements. This complex spectral overlap background noise makes it extremely difficult to accurately extract the net spectral line intensity of a single element, becoming the main technical bottleneck restricting the high-precision multi-element simultaneous quantitative analysis of titanium alloys by LIBS.

[0006] Therefore, there is an urgent need for a method and system for determining the composition of titanium alloys based on a spectrometer to solve the above-mentioned technical problems.

[0007] It should be noted that the information disclosed in this background section is only for understanding the background technology of the present invention, and therefore may include information that does not constitute prior art. Summary of the Invention

[0008] The purpose of this invention is to solve the problem in the prior art that the severe overlap and interference between the spectral lines of different elements makes it difficult to accurately extract the net spectral intensity of a single element, thus making it impossible to complete the composition determination.

[0009] To address the aforementioned technical problems, this invention proposes a method for determining the composition of titanium alloys based on a spectrometer, comprising the following steps:

[0010] The first laser pulse is focused onto the surface of the titanium alloy sample to be tested. The energy density of the first laser pulse is lower than the ablation threshold of the titanium alloy. The first laser pulse is used to generate an initial excitation region on the sample surface.

[0011] After a preset delay time following the application of the first laser pulse, a second laser pulse is applied to the initial excitation region; the polarization state of the second laser pulse is preset or actively modulated to a selected state;

[0012] During the second laser pulse, spectral signals emitted from the initial excitation region are acquired in at least two different preset polarization analysis directions to obtain polarization-resolved spectral data;

[0013] For each target element, the polarization-resolved spectral data is processed, and its response signal under a specific combination of polarization directions is calculated to obtain the characteristic analysis signal of the target element.

[0014] Based on the characteristic analysis signals of each target element, the composition content of each element in the titanium alloy sample to be tested is calculated.

[0015] Furthermore, the polarization state of the second laser pulse is preset to a fixed linear polarization state.

[0016] Furthermore, the at least two different preset polarization analysis directions are a first direction and a second direction that are perpendicular to each other.

[0017] Furthermore, the calculation of its response signal under a specific combination of polarization directions specifically involves: calculating the target element at its characteristic wavelength. At that point, the normalized differential signal of the spectral intensity in the first direction and the spectral intensity in the second direction. , , will the The value is used as the feature analysis signal, wherein, and These are the spectral intensities in the first and second directions, respectively. Indicates the pixel in time The time of data collection.

[0018] Furthermore, the calculation of component content based on the characteristic analysis signals of each target element includes the following steps:

[0019] For each target element, construct a physically guided quantitative factor. ,in , For the characteristic analysis signal of the target element, The characteristic analysis signal was obtained by calculating the characteristic spectral lines of the titanium matrix elements using the same method;

[0020] Based on the physical-guided quantitative factor The composition content of the target element is calculated.

[0021] Furthermore, the physical guidance quantitative factor Substitute the values ​​into the univariate linear calibration equation C = kR + b for calculation, where C is the element content, and k and b are coefficients determined by fitting the standard sample.

[0022] Furthermore, the wavelength of the second laser pulse is tuned to the resonant wavelength of a specific atomic or ionic energy level transition of the target element, which is achieved using a tunable laser.

[0023] Furthermore, the acquisition of the spectral signal emitted by the initial excitation region is achieved using a polarization analysis device, which is installed in front of the optical path entrance of the spectrometer to perform real-time separation and directional reception of the fluorescence signal in different preset polarization directions.

[0024] Furthermore, when the polarization analysis device is set to two orthogonal directions of 0° and 90°, the ratio of fluorescence intensity of the same element in the horizontal and vertical polarization states is obtained simultaneously. This ratio directly reflects the spatial orientation of its transition dipole moment and the symmetry of the local lattice field.

[0025] A spectrometer-based system for determining the composition of titanium alloys, comprising:

[0026] An initial excitation module is used to focus a first laser pulse onto the surface of the titanium alloy sample to be tested. The energy density of the first laser pulse is lower than the ablation threshold of the titanium alloy. The first laser pulse is used to generate an initial excitation region on the sample surface.

[0027] The secondary excitation module is used to apply a second laser pulse to the initial excitation region after a preset delay time following the application of the first laser pulse; the polarization state of the second laser pulse is preset or actively modulated to a selected state;

[0028] The spectral acquisition module is used to acquire the spectral signal emitted by the initial excitation region in at least two different preset polarization analysis directions during the second laser pulse, so as to obtain polarization-resolved spectral data.

[0029] The feature analysis module is used to process the polarization-resolved spectral data for each target element, calculate its response signal under a specific combination of polarization directions, and thus obtain the feature analysis signal of the target element.

[0030] The composition determination module is used to calculate the composition content of each element in the titanium alloy sample to be tested based on the characteristic analysis signals of each target element.

[0031] The beneficial effects of this invention are: by acquiring spectral signals in at least two different preset polarization analysis directions to obtain polarization-resolved spectral data, and calculating the response signal under a specific combination of polarization directions to obtain a feature analysis signal, it effectively suppresses isotropic background radiation and spectral line interference from non-target elements from a physical principle perspective, and obtains a feature analysis signal with high purity and strong specificity.

[0032] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the following figures. Attached Figure Description

[0033] Figure 1 This is a schematic flowchart of a method for determining the composition of titanium alloys based on a spectrometer, as described in this invention.

[0034] Figure 2 This is a schematic diagram of the module structure of a titanium alloy composition determination system based on a spectrometer according to the present invention. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0037] Example 1: As Figure 1As shown, this invention proposes a method for determining the composition of titanium alloys based on a spectrometer. This method is used in the composition testing process of titanium alloys and includes the following steps:

[0038] Step S1: Focus the first laser pulse onto the surface of the titanium alloy sample to be tested. The energy density of the first laser pulse is lower than the ablation threshold of the titanium alloy. The first laser pulse is used to generate an initial excitation region on the sample surface.

[0039] A laser pulse is a short, high-power-density coherent beam of light that can be generated by a solid-state laser, a fiber laser, or a gas laser. A laser pulse has an energy density, which refers to the laser energy contained per unit area on the cross-section of the beam, and is measured in J / cm².

[0040] Under the action of a laser pulse, the surface of the titanium alloy sample to be tested will undergo electronic transitions and changes in energy level layout due to nonlinear optical effects, surface desorption, or excitation effects, thereby generating an initial excitation region on the sample surface. This initial excitation region usually contains excited-state atoms, molecules, or weakly ionized particles. In order to prevent the surface of the titanium alloy sample to be tested from being ablated and damaged, the energy density of the first laser pulse needs to be lower than the ablation threshold of the titanium alloy to be tested. The specific value needs to be determined experimentally based on the specific composition, grain size, and surface condition of the titanium alloy, and is generally controlled in the range of 0.1 to 0.8 J / cm².

[0041] It should be noted that, in addition to controlling the energy density of the first laser pulse to be less than the ablation threshold of the titanium alloy under test, the pulse width should also be simultaneously adjusted to be within the range of 10 to 100 ps in order to balance excitation efficiency and thermal diffusion suppression; at the same time, the laser incident angle should be kept at 45°±3° to avoid signal deviation caused by reflectivity fluctuations.

[0042] Step S2: After a preset delay time following the application of the first laser pulse, a second laser pulse is applied to the initial excitation region; the wavelength of the second laser pulse is tuned to the resonance wavelength of the specific atomic or ion energy level transition of the target element; the polarization state of the second laser pulse is preset or actively modulated to a selected state.

[0043] After the first laser pulse forms the initial excitation region, a second laser pulse is applied to the initial excitation region after a preset delay time. The polarization state of the second laser pulse is preset or actively modulated to a selected state to enhance the selective resonance absorption efficiency of the excited-state particles of the target element, thereby improving the signal-to-noise ratio of the characteristic spectrum.

[0044] The polarization state refers to the trajectory and directional characteristics of the electric field vector of the laser wave as it propagates over time. It mainly includes linear polarization, circular polarization, elliptical polarization, and other states. For example, the polarization state can be set to linear polarization or circular polarization. For instance, before the measurement begins, based on the target element and known interference conditions, the polarization state of the second laser pulse can be set to a fixed optimal state (e.g., always set to horizontal linear polarization) once by using optical elements (such as a polarizer or waveplate with a fixed angle), thereby simplifying the system structure and improving repeatability.

[0045] In addition, active modulation can be performed, and the polarization state of the second laser pulse can be actively changed by electronically controlled or mechanically driven components (such as rotating waveplates, electro-optic modulators, liquid crystal polarization controllers, etc.) to dynamically adapt it between different measurement periods or different target elements, thereby achieving multi-element synchronous identification or dynamic suppression of interference peaks.

[0046] Furthermore, the wavelength of the second laser pulse needs to be tuned to the specific atomic or ionic energy level transition resonance wavelength of the target element. To achieve this, a tunable laser is required, including but not limited to optical parametric amplifiers, dye lasers, and tunable semiconductor lasers. Its output wavelength coverage must cover the typical transition spectra of common impurity elements (such as Fe, Al, V, and O) and the matrix element Ti in titanium alloys. For example, when the target element contains Fe, the wavelength of the second laser pulse needs to be precisely tuned to 238.204 nm, and when the target element contains Al, it needs to be tuned to 396.152 nm, thereby ensuring that the resonance absorption peak of each element is accurately excited and avoiding cross-interference caused by overlapping spectra.

[0047] Step S3: During the second laser pulse, the spectral signal emitted by the initial excitation region is acquired using a spectral acquisition system and a polarization analysis device in at least two different preset polarization analysis directions to obtain polarization-resolved spectral data.

[0048] To acquire the spectral signal, the spectral signal emitted from the initial excitation region needs to be acquired during the second laser pulse. The second laser pulse is synchronized with the acquisition time window. During this process, the target element atoms or ions resonantly excited by the second pulse are in an excited state and begin to emit characteristic fluorescence. Therefore, the spectral signal acquired at this time not only carries information about the element type, but also implicitly contains the polarization selection rules constraint of its local electromagnetic environment and energy level relaxation path. In the acquired signal at this time, the signal of the target element is maximized, while the background emission of other non-resonant elements is relatively weak, thereby improving the signal-to-noise ratio and element identification specificity.

[0049] To acquire the polarization-resolved spectral signal emitted from the initial excitation region, a spectral acquisition system is required, which is achieved using a polarization analysis device. This polarization analysis device can be a rotatable polarizer, a polarizing beam splitter prism, or an integrated polarization camera. It is installed in front of the optical path entrance of the spectrometer and is used to separate and receive the fluorescence signal in real time in different preset polarization directions.

[0050] For example, when the polarization analysis device is set to two orthogonal directions of 0° and 90°, the fluorescence intensity ratio of the same element in the horizontal and vertical polarization states can be obtained simultaneously. This ratio directly reflects the spatial orientation of its transition dipole moment and the symmetry of the local lattice field, thus providing a basis for judging the micro-regional distribution heterogeneity of impurity elements such as Fe and Al in titanium alloys and the phase interface segregation behavior.

[0051] The obtained polarization-resolved spectral data are a set of spectral pairs. Each spectral pair contains the intensity distribution of the same spectral channel in two orthogonal polarization directions, with its wavelength axis aligned with the intensity axis, which facilitates subsequent analysis.

[0052] For example, if the intensity ratio of the 0° to 90° polarization direction of the Fe element at 238.204 nm deviates from 1:1, it indicates that the Fe element has a preferred orientation distribution in the titanium matrix or is modulated by the lattice stress field, thus producing obvious polarization anisotropy.

[0053] Step S4: For each target element, process the polarization-resolved spectral data and calculate its response signal under a specific combination of polarization directions. The response signal is used to suppress isotropic background radiation and spectral line interference from non-target elements, thereby obtaining the characteristic analysis signal of the target element.

[0054] Specifically, a pixel-by-pixel ratio calculation is performed on each pair of polarization spectra, that is, the ratio of the intensity values ​​at corresponding wavelengths of the 0° and 90° polarization channels at the same spatial location is calculated, and its normalized polarization difference signal is calculated. This polarization difference signal is then used as the feature analysis signal of the target element. Specifically, the calculation formula is as follows:

[0055]

[0056] in, The polarization direction at 0° is at wavelength fluorescence intensity at that location The polarization direction is 90° at wavelength Fluorescence intensity at the location, subscript This indicates the acquisition time of the pixel at time t.

[0057] The specific meaning of the above formula is as follows: Since the continuous background radiation of plasma and most incoherent emission light are isotropic, their intensities in the 0° and 90° polarization directions are approximately equal. They can be canceled out by the above difference operation, thereby highlighting the characteristic signal of the target element with polarization anisotropy. Thus, it is preserved in the polarization difference signal, suppressing the interference of spectral background and spectral line overlap from the physical principle level. The obtained characteristic analysis signal has a higher signal-to-noise ratio and element specificity.

[0058] Step S5: Calculate the composition content of each element in the titanium alloy sample to be tested based on the characteristic analysis signals of each target element.

[0059] To achieve quantitative analysis, a quantitative calibration model between the characteristic analysis signal and the elemental content needs to be established in advance. The specific method of the above process is as follows: Select a series of titanium alloy standard samples whose chemical composition has been calibrated by common methods such as inductively coupled plasma mass spectrometry. Under the same experimental conditions (including laser parameters, delay time, and polarization settings), repeat steps S1 to S4 for each standard sample to obtain the characteristic analysis signal value P of each target element. Then, use partial least squares regression or other multivariate correction algorithms to establish a mathematical mapping relationship between P of each target element and its known mass fraction C, thus completing the construction of the quantitative calibration model. The known mass fraction C is provided by the standard sample certificate and covers the typical content range of common elements in titanium alloys (such as Al, V, Fe, O, etc.). For example, the Al content range is 0.5% to 6.5%, V is 0.5% to 4.0%, Fe is 0.05% to 0.50%, and O is 0.08% to 0.25%.

[0060] For an unknown titanium alloy sample, polarization spectra can be collected under the same experimental conditions, and the characteristic analysis signals P of each target element can be extracted. Substituting these signals into the constructed quantitative calibration model, the mass fraction C of the corresponding element can also be calculated. The specific implementation process can refer to existing technologies. For example, the measured spectral signals (intensity, intensity ratio, differential signals, etc.) can be correlated with the known concentrations of elements in the sample. Quantitative analysis of the unknown sample can be achieved through mathematical modeling. This method is a common method in the field of analytical instruments and will not be described in detail in this embodiment.

[0061] While the above process can improve analytical accuracy to some extent, its performance is still limited by the generalization ability and sample coverage of the calibration model. When the components of unknown samples deviate from the distribution range of standard samples, the prediction bias will increase. Therefore, the following improvements are still needed:

[0062] For each target element, instead of directly using the feature analysis signal value, a physically guided quantitative factor is constructed. ,in, ,in, The normalized parameter for the Ti matrix signal intensity ensures that the quantitative factor is not affected by laser energy fluctuations and differences in sample surface conditions. Its acquisition method is the same as that for P, i.e., the intensity of the characteristic spectral line of Ti element is collected under the same experimental conditions and processed in the same way. The specific meaning of the above physical guiding factor is the relative intensity of the target element signal relative to the titanium matrix signal, so that it is only strongly correlated with the relative content of the target element and weakly correlated with the experimental conditions.

[0063] In titanium alloys, titanium is the most abundant (typically >90%) and evenly distributed matrix element; therefore, The signal strength is strongly correlated with the overall excitation efficiency and plasma temperature density of the region affected by each laser pulse, among other common experimental conditions. Dividing P by... The obtained factor R is equivalent to performing an internal standardization of the target element signal using the matrix signal, thereby offsetting the signal fluctuations caused by common factors such as laser energy fluctuations and micro-region differences on the sample surface. This ensures that the R value mainly reflects only the relative concentration information of the target element, improving the robustness of quantitative analysis.

[0064] Then, the aforementioned process is performed under the same conditions to obtain the physical guidance quantitative factor value of each target element. With its corresponding known mass fraction C as the dependent variable and the factor value as the independent variable, a univariate linear regression is performed to obtain the calibration equation: C = kR + b, where k and b are regression coefficients determined by fitting standard sample data.

[0065] Because P and All signals are pure signals that have undergone polarization difference processing. Their ratio R and concentration C show a linear relationship. Therefore, only a simple univariate linear equation is needed to replace the multivariate correction model in the traditional spectral analysis process, thereby reducing the risk of overfitting and improving the transferability in cross-batch and cross-device scenarios.

[0066] Example 2: Figure 2 As shown, this embodiment provides a spectrometer-based titanium alloy composition determination system. This system operates the determination method described in Embodiment 1. The system includes:

[0067] An initial excitation module is used to focus a first laser pulse onto the surface of the titanium alloy sample to be tested. The energy density of the first laser pulse is lower than the ablation threshold of the titanium alloy. The first laser pulse is used to generate an initial excitation region on the sample surface.

[0068] The secondary excitation module is used to apply a second laser pulse to the initial excitation region after a preset delay time following the application of the first laser pulse; the polarization state of the second laser pulse is preset or actively modulated to a selected state;

[0069] The spectral acquisition module is used to acquire the spectral signal emitted by the initial excitation region in at least two different preset polarization analysis directions during the second laser pulse, so as to obtain polarization-resolved spectral data.

[0070] The feature analysis module is used to process the polarization-resolved spectral data for each target element, calculate its response signal under a specific combination of polarization directions, and thus obtain the feature analysis signal of the target element.

[0071] The composition determination module is used to calculate the composition content of each element in the titanium alloy sample to be tested based on the characteristic analysis signals of each target element.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining the composition of titanium alloys based on a spectrometer, characterized in that: Includes the following steps: The first laser pulse is focused onto the surface of the titanium alloy sample to be tested. The energy density of the first laser pulse is lower than the ablation threshold of the titanium alloy. The first laser pulse is used to generate an initial excitation region on the sample surface. After a preset delay time following the application of the first laser pulse, a second laser pulse is applied to the initial excitation region; the polarization state of the second laser pulse is preset or actively modulated to a selected state; During the second laser pulse, spectral signals emitted from the initial excitation region are acquired in at least two different preset polarization analysis directions to obtain polarization-resolved spectral data; For each target element, the polarization-resolved spectral data is processed, and its response signal under a specific combination of polarization directions is calculated to obtain the characteristic analysis signal of the target element. Based on the characteristic analysis signals of each target element, the composition content of each element in the titanium alloy sample to be tested is calculated. The polarization state of the second laser pulse is preset to a fixed linear polarization state; The at least two different preset polarization analysis directions are a first direction and a second direction that are perpendicular to each other; The calculation of its response signal under a specific combination of polarization directions specifically involves: calculating the target element's response signal under a specific polarization direction combination. At its characteristic wavelength λ, the normalized difference signal P between the spectral intensity in the first direction and the spectral intensity in the second direction is given by P = I∥λt−I⊥λt÷I∥λt+I⊥λt. The value of P is used as the characteristic analysis signal, where I∥λ and I⊥λ are the spectral intensities in the first and second directions, respectively, and t represents the acquisition time of the target element at time t.

2. The method for determining the composition of titanium alloys based on a spectrometer according to claim 1, characterized in that: The calculation of component content based on the characteristic analysis signals of each target element includes the following steps: For each target element, construct a physically guided quantitative factor. ,in , For the characteristic analysis signal of the target element, The characteristic analysis signal was obtained by calculating the characteristic spectral lines of the titanium matrix elements using the same method; Based on the physical-guided quantitative factor The composition content of the target element is calculated.

3. The method for determining the composition of titanium alloys based on a spectrometer according to claim 2, characterized in that: The physical guidance quantitative factor Substitute the values ​​into the univariate linear calibration equation C = kR + b for calculation, where C is the element content, and k and b are coefficients determined by fitting the standard sample.

4. The method for determining the composition of titanium alloys based on a spectrometer according to claim 1, characterized in that: The wavelength of the second laser pulse is tuned to the resonant wavelength of a specific atomic or ion energy level transition of the target element, and this process is achieved using a tunable laser.

5. The method for determining the composition of titanium alloys based on a spectrometer according to claim 4, characterized in that: The acquisition of the spectral signal emitted by the initial excitation region is achieved using a polarization analysis device, which is installed in front of the optical path entrance of the spectrometer to perform real-time separation and directional reception of the fluorescence signal in different preset polarization directions.

6. The method for determining the composition of titanium alloys based on a spectrometer according to claim 5, characterized in that: When the polarization analysis device is set to two orthogonal directions, 0° and 90°, the ratio of fluorescence intensity of the same element in the horizontal and vertical polarization states is obtained simultaneously. This ratio directly reflects the spatial orientation of its transition dipole moment and the symmetry of the local lattice field.

7. A spectrometer-based titanium alloy composition determination system, used to implement the spectrometer-based titanium alloy composition determination method according to any one of claims 1 to 6, characterized in that: include: An initial excitation module is used to focus a first laser pulse onto the surface of the titanium alloy sample to be tested. The energy density of the first laser pulse is lower than the ablation threshold of the titanium alloy. The first laser pulse is used to generate an initial excitation region on the sample surface. The secondary excitation module is used to apply a second laser pulse to the initial excitation region after a preset delay time following the application of the first laser pulse; the polarization state of the second laser pulse is preset or actively modulated to a selected state; The spectral acquisition module is used to acquire the spectral signal emitted by the initial excitation region in at least two different preset polarization analysis directions during the second laser pulse, so as to obtain polarization-resolved spectral data. The feature analysis module is used to process the polarization-resolved spectral data for each target element, calculate its response signal under a specific combination of polarization directions, and thus obtain the feature analysis signal of the target element. The composition determination module is used to calculate the composition content of each element in the titanium alloy sample to be tested based on the characteristic analysis signals of each target element. The polarization state of the second laser pulse is preset to a fixed linear polarization state; The at least two different preset polarization analysis directions are a first direction and a second direction that are perpendicular to each other; The calculation of its response signal under a specific combination of polarization directions specifically involves: calculating the target element's response signal under a specific polarization direction combination. At its characteristic wavelength λ, the normalized difference signal P between the spectral intensity in the first direction and the spectral intensity in the second direction is given by P = I∥λt−I⊥λt÷I∥λt+I⊥λt. The value of P is used as the characteristic analysis signal, where I∥λ and I⊥λ are the spectral intensities in the first and second directions, respectively, and t represents the acquisition time of the target element at time t.

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