CN114235576B - Method for qualitatively analyzing weakest interface of multilayer heterogeneous gradient material by stretching single shear method - Google Patents
Method for qualitatively analyzing weakest interface of multilayer heterogeneous gradient material by stretching single shear method Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 52
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- 238000010008 shearing Methods 0.000 claims abstract description 16
- 239000007769 metal material Substances 0.000 claims abstract description 6
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
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- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/0003—Steady
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0017—Tensile
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0025—Shearing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/006—Crack, flaws, fracture or rupture
- G01N2203/0067—Fracture or rupture
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Abstract
The invention discloses a method for qualitatively analyzing the weakest interface between different layers of a multi-layer material by stretching a sample overlapped with different interfaces. The gradient heterogeneous materials with three layers and more are processed into an integrated ladder structure similar to lap joint, and axial stretching is carried out in the same mode as a general metal material sample stretching test in form, and single shearing operation and observation are simultaneously carried out on a plurality of layers of different material bonding interfaces. In the testing process, all the shearing strengths of interfaces between different material layers are different, wherein the material interface with the weakest shearing strength of the interface is damaged and fails firstly due to the shearing force in the stretching process, so that the weakest interface in the multi-layer heterogeneous gradient material is qualitatively obtained. The method can rapidly judge the weakest interface of the multi-layer heterogeneous gradient material, provides basic criteria and directions for the design and improvement of the multi-layer heterogeneous gradient material, and has the advantages of less consumable materials, short time, simple form and low cost.
Description
Technical Field
The invention relates to the field of mechanical detection qualitative analysis, in particular to a method for qualitatively analyzing the weakest interface of a powder metallurgy metal-based multilayer heterogeneous gradient material by utilizing a stretching method to enable a sample to generate shear damage.
Technical Field
The gradient multilayer heterogeneous material of powder metallurgy is one of the future development directions of multifunctional and high-performance materials. The material can combine the advantages of various heterogeneous alloys, such as titanium alloy has excellent performances of high corrosion resistance, high temperature impact resistance and the like, magnesium alloy has the advantages of high damping property and low density, and aluminum alloy has good electric conduction and heat conduction properties and good plasticity, so that the materials can be subjected to gradient compounding to obtain good high-temperature and high-pressure resistant light-weight and impact resistant materials. The materials generally have higher strength-to-weight ratio, excellent corrosion resistance, high specific strength, lower density and good impact resistance caused by excellent strength and toughness, and have unique and excellent performances in the application fields of high and new technologies such as military, aerospace and the like. In order to achieve good fusion of these excellent properties, research on the bonding interface between different material layers of a powder metallurgy gradient multilayer heterogeneous material is of great importance.
In general, the shear strength of a lap joint interface can be obtained by lapping two different materials and performing a single shear test on the lap joint interface, and the shear strength is a characteristic very suitable for characterizing the interface strength between materials which are lapped together, and the strongest and weakest interfaces in the mechanical property in the gradient materials can be found by comparing the shear strength on the interfaces. In general, in the related research, the focus is on how to solve the problem caused by the interface with the weakest strength. However, this method generally only can test one interface strength between two different materials, and when there are multiple interfaces in the powder metallurgy gradient composite material and the weakest interface is to be found out rapidly, testing multiple interfaces separately is not only troublesome and time-consuming, but also causes a lot of material loss, and for powder metallurgy gradient materials with smaller layer thickness, the difficulty of preparing test samples by taking two layers is relatively large, and the accuracy is not well guaranteed. Meanwhile, many powder metallurgy gradient materials are integrally molded by unified sintering after powder spreading, so that the integrity of the process can be guaranteed, when a single interface is to be measured by the multi-layer material, materials of other layers and redundant bonding interfaces are required to be completely removed, a large amount of materials are wasted, and meanwhile, the process for preparing samples for the same material for multiple times is time-consuming and labor-consuming.
Therefore, a method for qualitatively analyzing the weakest interface of the multilayer gradient heterogeneous composite material, which has the advantages of simple parameter setting, rapid and convenient operation and relatively high accuracy, is needed to be designed.
Disclosure of Invention
In the actual research and development process, the following steps are found:
1. in the tensile test of a general gradient heterogeneous material, the interface or the material layer which is broken first by a tensile sample is not necessarily the lowest in tensile strength, and the interface or the material layer which is broken first by the low-elongation high-tensile strength is possibly generated due to different elongation, so that misleading is generated on the research direction;
2. even if the multi-layer gradient heterogeneous material sample is in the same position in the tensile test and the multi-layer material breaks and fails, the initial starting point of failure is difficult to judge, which has adverse effects on the selection of the microscopic research point of the subsequent breaking port and the idea planning of subsequent adjustment and reinforcement. In the engineering experiment problem exploration, the rapid and accurate qualitative analysis of the strength of each layer of the gradient multilayer heterogeneous material is an important and efficient research requirement;
3. the method can quantitatively characterize the bonding strength of different materials on two interfaces, but for research of multi-layer gradient heterogeneous materials, the method for quantitatively researching the bonding strength between two interfaces at one time is too low, and meanwhile, the bonding condition of two interfaces in the multi-layer material cannot represent the overall performance of the material, and the multi-layer test is needed. In general, research and improvement of materials will be initiated from the weakest item, and thus the research of the interface with the weakest bonding strength in a multilayer gradient heterogeneous material is most valuable.
Based on the research, in order to overcome the defects and shortcomings of the prior art, the invention aims to provide a method for rapidly and qualitatively judging the weakest bonding interface of a powder metallurgy gradient heterogeneous material under the condition of multiple bonding surfaces; the method can realize that the bonding interface with the weakest bonding strength in the powder metallurgy multilayer heterogeneous gradient material can be distinguished through one-time test of a single sample, and has the advantages of simple parameter setting, quick and convenient operation, easy acquisition of test equipment and conditions, relatively easy sample preparation, less material consumption and low cost.
In order to achieve the above purpose, the scheme of the invention is divided into three steps: including sample preparation processing, sample clamping and sample shear tensile testing.
Sample preparation treatment refers to: obtaining a powder metallurgy gradient composite material with proper size as a raw material, and processing the material into the shape and specification of a sample shown in a corresponding diagram after wire cutting and surface treatment; removing oxide layers which may be generated on the exposed surfaces of different alloys; cleaning and drying the sample and polishing the sample to be smooth;
sample clamping refers to: adjusting gaskets with proper sizes are additionally arranged at the head end and the tail end of the sample, so that the whole upper end and the whole lower end of the sample clamped by the universal mechanical instrument clamp are kept parallel to the applied stretching force;
the tensile shear test of the sample refers to: after the sample is clamped, the universal mechanical instrument is started according to a general tensile test method, and the sample is stretched until the sample fails and breaks. If the breaking position of the sample is on the joint surface of two layers of materials, judging the strength of the joint surface as the weakest one of all joint surfaces in the materials; the weak sample fracture site is not at the bonding surface but at one layer of metal material in the sample, which indicates that the alloy material has weaker tensile strength than the bonding strength of the weakest bonding surface in the sample.
The invention relates to a method for qualitatively analyzing the weakest interface of a multi-layer heterogeneous gradient material by using stretching single shear,
the multilayer heterogeneous gradient material consists of An A1 material layer, an A2 material layer and An material layer; wherein n is an integer of 2 or more; processing the multi-layer heterogeneous gradient material into a stepped sample according to different materials; according to the material and the step layers, forming a one-to-one correspondence, processing n material layers into samples with n steps (for example, processing an A1 material layer into A1 st step, processing an A2 material layer into A2 nd step and processing an n material layer into an n th step), wherein the area of the joint of any two steps is more than or equal to 5% of the area of the corresponding step; the thickness of any one step must be equal to the thickness of the corresponding material layer (i.e. the step structure is processed according to the original arrangement structure of the gradient materials, and the original hierarchy structure of the gradient materials is reflected in the thickness direction of the sample); when n is greater than 2, the projection shape of the A2 material layer in the direction vertical to the plane is equal to any one layer from A2 to An-1, the projection area size and the projection shape of the lap joint part between all the material layers in the direction vertical to the plane are also equal, and the total thickness of each step n is greater than or equal to 0.5mm; the sample is then stretched using a stretching apparatus until broken.
As a preferred scheme, the method for qualitatively analyzing the weakest interface of the multi-layer heterogeneous gradient material by using the stretching single shear has the whole length of a sample not smaller than 40mm, preferably 80-140mm, and the sample comprises a holding end and a non-holding part; the width of the clamping end is not less than 3mm, preferably 15-25mm, the length of the clamping end is not less than 3mm, preferably 15-25mm, and corresponds to the parallel section part of a general metal stretching plate sample, wherein the width of the sample is not less than 0.5mm, preferably 5-10mm.
The overall thickness d of the standard sample is not less than 0.5mm in the invention to provide sufficient stability and test accuracy; the thickness of each heterogeneous material layer of the tested sample material body is not required to be consistent; when the sample is clamped for testing, metal gaskets with proper thickness can be attached to the head end and the tail end of the sample so as to keep the thickness and the horizontal height of the two clamping ends consistent and ensure the stability and the precision of the testing process.
As a preferred embodiment, the invention provides a method for qualitatively analyzing the weakest interface of a multi-layer heterogeneous gradient material by using a tensile single shear, wherein the length of the non-clamping part of the sample is 30-200mm, preferably 60-120mm.
As a preferable scheme, the method for qualitatively analyzing the weakest interface of the multi-layer heterogeneous gradient material by using the stretching single shear is characterized in that the thicknesses of the heterogeneous material layers of the tested sample material body are equal or unequal.
As a preferred scheme, the method for qualitatively analyzing the weakest interface of the multi-layer heterogeneous gradient material by using the stretching single shear processes the multi-layer heterogeneous gradient material into a stepped sample according to different materials; according to the material and the step layers, forming a one-to-one correspondence, and processing n material layers into n step-shaped samples; then cutting and polishing are carried out on the basis of the existing materials until the surface roughness Ra is 3-12.5, preferably Ra3.2.
As a preferable scheme, the method for qualitatively analyzing the weakest interface of the multi-layer heterogeneous gradient material by using the stretching single shear is characterized in that an obtained sample is horizontally placed on a plane and is projected perpendicular to the plane; the projected profile and dimensions conform to those of the projected profile and dimensions of the sheet stretched sample defined in national standard GBT 228-2002.
In practical application, the sample is prepared by the following steps: the sample pair obtained by adopting the wire cutting is characterized in that the existing powder metallurgy gradient composite material is firstly processed into a form shown in a three-dimensional view, then cutting processing is carried out on the existing powder metallurgy gradient composite material on the basis of the existing powder metallurgy gradient composite material, and polishing is carried out (the powder metallurgy gradient composite material is manually or mechanically polished to the surface roughness of about 6 levels after wire cutting, namely Ra=3.2), the size of the powder metallurgy gradient composite material is shown in fig. 4, the whole powder metallurgy gradient composite material is consistent with a plate sample tested by metal quasi-static stretching from the overlooking angle, and the powder metallurgy gradient composite material is in a 'step' structure in the side view direction of the sample.
As a preferred scheme, the method for qualitatively analyzing the weakest interface of the multi-layer heterogeneous gradient material by using the stretching single shear is characterized in that in the sample preparation, the width of each bonding surface is required to be consistent, and the width of each bonding surface is in the range of 0.5-10 mm (namely, the width of a parallel section). Keeping the widths of the bonding surfaces consistent is beneficial to ensuring that the area shapes of the bonding surfaces are consistent, so that the shearing stress of the bonding surfaces is consistent before fracture occurs, and the weakest bonding interface can be indicated when the bonding interfaces which fracture first occur under the condition that the shearing stress is consistent. The bonding surface width is kept consistent with the parallel section width for convenient processing and without additional and unnecessary structural stress concentration so as to prevent failure at an unexpected part in the sample testing process.
As a preferable scheme, the method for qualitatively analyzing the weakest interface of the multi-layer heterogeneous gradient material by using the stretching single shear has the advantages that the length of each joint surface is 0.5-3 mm, the length of each joint surface is kept consistent, and the total area occupation ratio of the joint position is ensured to be far smaller than the total area of parallel sections of a sample in a overlooking view angle of the sample. The uniform length of the bonding surfaces is beneficial to ensuring that the shape and the area of each bonding interface are uniform so as to ensure that the shearing stress of each bonding surface is uniform before fracture occurs. The total area of the bonding sites is much smaller than the total area of the parallel segments in order to reduce the upper limit of shear stress that each bonding interface can withstand, ensuring that the fracture occurs at the bonding interface rather than at the parallel segments, ensuring that the test is effective for the purpose of detecting the weakest bonding interface.
As a preferable scheme, the method for qualitatively analyzing the weakest interface of the multi-layer heterogeneous gradient material by using the stretching single shear has the thickness of 0.1-2 mm of the single-layer material of the sample. Considering the general thickness range of the actual powder metallurgy gradient material and the precision of wire cutting processing, the single-layer material thickness of a sample of 0.1mm-2mm can be suitable for most of multi-layer heterogeneous gradient materials, in most cases, the raw materials to be tested can be directly cut into the samples required by the test in a machining mode, time and materials are saved, and the thickness and structure of the raw material layers are not required to be readjusted to meet the sample requirements, so that errors possibly caused by the test are reduced, and the test precision is improved.
The whole test of the invention is kept in the category of quasi-static tensile test under the sample with the same size specification, so as to ensure the stability of the test.
As a preferred scheme, the method for qualitatively analyzing the weakest interface of the multi-layer heterogeneous gradient material by using the stretching single shear comprises the following steps:
step one
Preparing a test sample of the gradient heterogeneous composite material to be tested according to the requirement;
step two
Metal gaskets with proper thickness, size and shape are additionally arranged at the two clamping ends of the sample;
step three
Referring to the normal metal material plate sample tensile test step, loading a universal mechanical test instrument capable of executing quasi-static stretching of the metal material, and fixing by using a clamp;
step four
Setting the stretching speed to be 1mm/min;
starting stretching until the bonding interfaces of different layers of materials of the sample cannot bear shearing stress and are broken on a material bonding plane, wherein the broken bonding plane reflects the weakest bonding interface of the tested multi-layer heterogeneous gradient composite material; if the failure position of the sample after the test is not on the bonding interface of the heterogeneous materials, the strength of each bonding interface of the gradient material is larger than that of the material layer with the weakest strength in each heterogeneous material layer.
The universal mechanical instrument can be provided with a clamp with a proper size, the loading force can reach 15kN and above, and the normal quasi-static tensile test can be completed; the sample with the gasket is clamped by using the universal mechanical instrument clamp, the tensile force provided in the process of the test can be a shearing force acting on the bonding layers of different materials, and when the shearing strength generated by the shearing force is greater than the limit born by the bonding surfaces, the fracture can occur on the bonding surfaces, and the bonding surfaces which are firstly fractured are the weakest bonding surfaces because the shearing strengths of the different bonding surfaces are different. Therefore, the invention can rapidly judge the weakest joint surface in a plurality of joint surfaces in the material under the condition of only one experiment, saves a great deal of time and basic materials, and has short time consumption, low cost, wide applicable instrument and range and good application prospect.
The temperature of the test environment related in the invention is kept within the range of 15-30 ℃, so that the material is prevented from being too brittle due to low temperature, or the strength of the material is prevented from being influenced by high temperature, so that the test accuracy is prevented from being influenced.
Principle and advantages
Aimed structural advantages:
1. structural characteristics of the powder metallurgy gradient material: multilayer multi-gradient powder metallurgy. In general, one of the most commonly used preparation methods of powder metallurgy gradient materials is hot-press sintering, which means that different raw material materials are layered in a mold at one time, and then sintered and formed under the synergistic effect of high temperature and high pressure, so that the prepared materials have a multi-layer structure, and the materials with different materials are correspondingly paved in different powder paving sequences at different depths. The unique sample structure designed by the patent is designed aiming at the structural characteristics of gradient powder metallurgy materials, the required detection materials are assumed to be of a three-layer structure, each layer of material is different from the other layer of material, and two different material combination interfaces are arranged on the sample, for example, a first material, a second material and a third material are three different materials as shown in the schematic diagram of the patent, and the sample is subjected to linear cutting and cutting processing after sintering and forming to obtain the sample with the ladder-shaped structure in the figure. The stepped sample structure can ensure that the interfaces between each different material layer are exposed, and the different layers are connected only by virtue of the bonding interfaces, namely, when axial loading is carried out in the subsequent test, the whole sample is connected by virtue of the rest bonding interfaces between the materials of the different layers, so that qualitative comparison detection of the mechanical strength of the material bonding layers can be obtained in the test, and the position of the bonding layer with the relatively weakest bonding strength is deduced;
2. to ensure that the weakest bonding interface can be detected in the test, the sample structural design is substantially identical to the sheet specimen of a typical quasi-static tensile test in the top view direction (fig. 3) because structural stress concentration is ensured by the circular arc segments such that fracture failure occurs in the parallel segments. At the same time, a certain material layer thickness and a smaller bonding layer area should be ensured to ensure that failure conditions occur on the material bonding layer rather than on the individual layers of material during testing. For example, the bonding layer between the first and second materials is the weakest, and failure should occur where the first and second material layers overlap, but not on the first or second material layers. When the sample is cut, in order to ensure that only the exposed bonding part plays a mechanical role, (namely, only the overlapping position of different material layers on the sample still exists the material bonding layer between the different layers), the bonding layer of the materials of the first layer, the second layer and the third layer on the sample except the bonding part is completely cut, that is, for example, in the case of the first material layer portion of the sample, the exposed surface thereof is free of any residue of the bonding layer bonded to the second material, and the bonding layer resulting from the fusion of the first material and the second material is present in the sample at the location where the first material and the second material are bonded.
3. The material shown in the patent drawings only takes three layers of gradient materials as an example, and in practical terms, the number of layers of the gradient materials can be measured by the method without too large limitation, the number of layers of the material is at least two, and the number of layers is at most not limited, and the upper limit of a machine and the limitation of the original preparation technology still need to be considered in practical application. If a sample with more than three layers of materials is needed to be measured, the area and the shape of the joint part between different layers of the sample are ensured to be unchanged, and a plurality of rectangular layers similar to the second material layer are added in the middle according to the total layer number of the materials. If the gradient material is 4 layers, and the material sequence is one, two, three and four, then the second material layer is combined with the third material layer, the projected area shape of the third material layer in the direction vertical to the plane is completely consistent with the second material layer, and the shape and the size of the combining position of the third material layer and the second material layer are completely consistent with the shape and the size of the combining position of other material layers. In the above described case, the greater the number of layers of gradient material to be tested, the longer the length of the sample to be processed may be, since more layers of material need to be exposed, and the thicker the auxiliary pad for balancing in fig. 1 will be to ensure that the sample is entirely parallel to the vertical direction when the sample is clamped.
Compared with the existing test method, the invention has the following advantages:
1. the instrument and equipment used in the invention are simple and easy to obtain;
2. the sample required by the invention is easy to prepare and the preparation method of the material does not need to be readjusted;
3. the invention has the advantages of less material consumption, short time consumption and low cost (compared with the traditional layering sequential detection mode, the material consumption is 1/2 to 1/(n-1), n is the number of layers of gradient material, and the time consumption is 1/2 to 1/(n-1), mainly because the required test times can carry out quick qualitative test on the bonding interface strength of the materials only once for single material, and find the interface with the weakest bonding acting force);
the invention has some extreme cases in practical tests, and the following concrete expression and coping methods are as follows:
1. when the bonding properties and strength of two or more material layers in the tested multi-layer heterogeneous gradient material are close, another interface with similar strength can be damaged when the weakest interface breaks or the broken interface is not the result of the interface with the lowest bonding strength in fact when tested by the method. Aiming at the possible situation, the invention adopts technical adjustment, and the specific direction is to adjust the stretching speed of the testing instrument according to the experimental situation and the characterization of fracture morphology. In theory, the performance difference between different bonding layers can be effectively amplified by reducing the existing stretching rate (1 mm/min) and controlling the rate within the quasi-static stretching rate range specified by national standard GBT228-2002 (specifically according to the actual parameters of the sample). This is because when the existing stretching rate is reduced, each bonding interface under the action of the shearing force will have a longer time for the dislocation to migrate, and the more the dislocation migrates, the more the work the material bonding layer itself absorbs, so that the energy absorbed by the bonding interface before fracture is more approximate to its theoretical value, in this state, the difference between bonding interfaces between the materials is further reflected, and the experimental result finally presented is more stable.
2. When an extreme condition that the strength of a material layer of a certain gradient heterogeneous material is far lower than that of a bonding layer between materials occurs, the situation that the material layer on a sample breaks before the bonding layer occurs is likely to occur in an experiment. In such cases, the reinforcement of the exposed frangible material layer may be directed to stretching the frangible material layer in a constrained state to prevent premature fracture thereof. In a specific embodiment, more auxiliary gaskets are added on the sample, or the fragile material layer is reinforced by using engineering adhesive, for example, an additional material with certain strength is adhered to the surface of the fragile material layer by using 502 glue for reinforcement. The projection of the reinforced sample in the direction vertical to the plane is consistent with that before the reinforcement, the reinforcement cannot lead the overall maximum thickness of the sample to exceed the maximum thickness before the reinforcement, and the main bearing part is still the joint part between the material layers. The testing procedure of the reinforced sample is identical to the original procedure of the invention.
Drawings
FIG. 1 is a schematic view of a vertical three-dimensional structure of a sample for testing the weakest bonding interface of a gradient heterogeneous multi-layer material according to the present invention;
FIG. 2 is a schematic view of a transverse three-dimensional structure of a sample for testing the weakest bonding interface of a gradient heterogeneous multi-layer material according to the present invention;
FIG. 3 is a two-dimensional top view of a sample of the weakest bonding interface for testing a graded heterogeneous multilayer material according to the present invention.
FIG. 4 is a schematic diagram of a standard workpiece designed according to the present invention for testing the sample size and structure of the weakest bonding interface sample of the gradient heterogeneous multi-layer material.
Detailed Description
Example 1
The first embodiment is a qualitative testing method for the weakest bonding interface of the titanium aluminum magnesium powder metallurgy gradient composite material, which comprises the steps of sample preparation treatment, sample clamping and sample tensile shear testing as shown in the first figure.
The sample preparation process is specifically as follows:
the gradient heterogeneous materials (namely the titanium aluminum magnesium powder metallurgy gradient composite material) are processed by a linear cutting method to form a stepped sample, and the sample is broken on the bonding interface of different heterogeneous materials. Taking three layers of heterogeneous gradient materials as an example, unlike the samples generally used for quasi-static tensile test or single shear test, the samples required by the method are divided into three parts, as shown in fig. 1, the first part is material 1, the second part is material 2, the third part is material 3, and the area and shape of the lap joint interface 1 and the interface 2 are the same, the single lap joint interface occupies the second part (the first part and the third part have larger area than the second part due to the inclusion of clamping sections, and the area volume is necessarily larger than that of the second part, so the second part is taken as a main reference), the area of the lap joint interface is larger than or equal to 5% of the overlooking surface area (actually, the lap joint interface of the two occupies 10% of the area of the second part), and the area of the lap joint interface is larger than or equal to 2% of the area of the first part or the third part in overlooking direction (actually, the single lap joint interface occupies 3% of the overlooking surface of the first part or the third part);
for the composite material samples with 4 layers and above, processing is carried out according to the original arrangement structure of the gradient materials according to the ladder structure, and the hierarchical structure of the original gradient materials is reflected in the thickness direction of the sample.
Then cutting and polishing (the Ra=3.2 after linear cutting is manually or mechanically polished to the surface roughness of about 6 level), the dimension of which is shown in figure 4 (the sample length is 100mm, the width of the sample clamping end is 20mm, the length of the sample clamping end is 20mm, the radius of the circular arc section of the sample is R=20 mm, the thickness of each layer of material layer of the sample is 2mm, the width of the parallel section of the sample is 6mm, the length of the first part and the third part of the sample is 38mm, the length of the second part of the sample is 30mm, the overlap joint of the two parts and the third part is 3mm, the thickness of the adjusting gasket is 4mm, the width and the length are 20 mm), the whole is consistent with the plate sample tested by metal quasi-static tension from the overlooking angle, and the plate sample is in a 'ladder' structure in the side view direction of the sample.
The sample clamping procedure refers to: adjusting gaskets with the same size (the thickness is 4mm, the length and the width are 20 mm) are added at two ends of the sample, so that the sample is parallel to the tensile force; any end of the sample is the head; the lap joint width of each layer of the bonding surface is 6mm; the clamp is closed, clamping the sample.
The sample tensile shear test was: starting a universal mechanical instrument, adjusting the stretching speed to be 1mm/min until the sample is broken, and setting the loading force to be 10kN; due to the effects of the sample structure and the tensile stress, corresponding shearing force is generated on the overlapped joint surfaces between the layers of the sample, when the shearing stress caused by the loading of a machine breaks through the bonding strength of a certain overlapped interface, the interface is broken and fails first, the experiment is automatically terminated under the control of a computer program, at the moment, the sample is observed to obtain which overlapped interface between two layers of materials breaks, and the weakest combined interface between the layers in the materials is deduced to be the material combined interface where the breaking occurs. Meanwhile, according to the loading load recorded by the experimental program and the designed size of the sample, the bonding strength of the weakest bonding interface of the sample can be calculated and derived.
In the first embodiment, testing a gradient heterogeneous material sample compounded by titanium alloy, aluminum alloy and magnesium alloy in sequence, wherein the sample is firstly disconnected on an interface of the magnesium alloy and the aluminum alloy in the testing process, which shows that the strength of the aluminum-magnesium interface is weakest; the shear strength obtained by the conventional single shear test shows that the bonding interface strength of titanium and aluminum is larger than that of aluminum and magnesium, which proves the effectiveness of the test of the invention.
The foregoing examples are illustrative of the present invention and are not intended to limit the scope of the invention in any way, and any other modifications, substitutions, combinations, simplifications or equivalents which do not depart from the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (9)
1. A method for qualitatively analyzing the weakest interface of a multi-layer heterogeneous gradient material by using stretching single shear is characterized in that:
the multilayer heterogeneous gradient material consists of An A1 material layer, an A2 material layer and An material layer; wherein n is an integer of 2 or more; processing the multi-layer heterogeneous gradient material into a stepped sample according to different materials; according to the material and the step layers, forming a one-to-one correspondence, processing n material layers into n step-shaped samples, wherein the area of the overlapping part of any two steps is more than or equal to 5% of the corresponding step area; the thickness of any one step must be equal to the thickness of the corresponding material layer; and the total thickness of each step n is more than or equal to 0.5mm; the sample is then stretched using a stretching apparatus until broken.
2. The method for qualitatively analyzing the weakest interface of a multi-layer hetero-gradient material using tensile single shear according to claim 1, wherein: the total length of the sample is 80-140mm, and the sample comprises a clamping end and a non-clamping part; the width of the clamping end is 10-20mm, the length of the clamping end is 10-15mm, the clamping end corresponds to the parallel section part of a common metal stretching plate sample, and the width of the sample is not less than 0.5mm.
3. The method for qualitatively analyzing the weakest interface of a multi-layer hetero-gradient material using tensile single shear according to claim 1, wherein: the length of the non-clamping portion of the sample is 30-200mm.
4. The method for qualitatively analyzing the weakest interface of a multi-layer hetero-gradient material using tensile single shear according to claim 1, wherein: the thickness of each heterogeneous material layer of the tested sample material body is equal or unequal.
5. A method for qualitatively analyzing the weakest interface of a multilayer heterogeneous gradient material using tensile single shear as claimed in claim 2, wherein:
processing the multi-layer heterogeneous gradient material into a stepped sample according to different materials; according to the material and the step layers, forming a one-to-one correspondence, and processing n material layers into n step-shaped samples; then cutting and polishing are carried out on the basis of the prior art until the surface roughness Ra is 3-12.5.
6. A method for qualitatively analyzing the weakest interface of a multilayer heterogeneous gradient material using tensile single shear as claimed in claim 2, wherein: horizontally placing the obtained sample on a plane, and projecting the sample perpendicular to the plane; the projected profile and dimensions are consistent with the projected profile and dimensions of the sheet stretched sample defined in national standard GBT 228-2002.
7. A method for qualitatively analyzing the weakest interface of a multilayer heterogeneous gradient material using tensile single shear as claimed in claim 2, wherein: in the sample preparation, the width of each bonding surface needs to be kept consistent, and the width of each bonding surface ranges from 0.5mm to 10mm.
8. A method for qualitatively analyzing the weakest interface of a multilayer heterogeneous gradient material using tensile single shear as claimed in claim 2, wherein: the thickness of the sample single-layer material is 0.1mm-2 mm.
9. The method for qualitatively analyzing the weakest interface of a multi-layer hetero-gradient material using tensile single shear according to claim 2, wherein the method comprises the steps of; the method comprises the following steps:
step one
Preparing a test sample of the gradient heterogeneous composite material to be tested according to the requirement;
step two
Metal gaskets with the same thickness, size and shape are additionally arranged at the two clamping ends of the sample;
step three
Referring to the normal metal material plate sample tensile test step, loading a universal mechanical test instrument capable of executing quasi-static stretching of the metal material, and fixing by using a clamp;
step four
Setting the stretching speed to be 1mm/min; the loading force is 1 kN-30 kN;
starting stretching until the bonding interfaces of different layers of materials of the sample cannot bear shearing stress and are broken on a material bonding plane, wherein the broken bonding plane reflects the weakest bonding interface of the tested multi-layer heterogeneous gradient composite material; if the failure position of the sample after the test is not on the bonding interface of the heterogeneous materials, the strength of each bonding interface of the gradient material is larger than that of the material layer with the weakest strength in each heterogeneous material layer.
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