Microbridge Tensile Test Model And Study On Fracture Toughness Of CuZr Amorphous Alloy Film

The thickness of thin film materials is often limited to micron or even sub-micron sizes,and the traditional fracture toughness test methods of bulk materials cannot be applied to thin film materials.The previous research of the research group proposed the micro-bridge stretching method for the fracture toughness of the film.By loading the macro-size substrate sample,the uniaxial tensile test of the micro-film sample on the substrate surface was realized,but this method has no advantages in sample preparation and testing.To achieve standardization,the mechanical model of the core link needs to be studied in depth,which restricts the practical application of this method.This research is funded by the National Fund("Study on the Microbridge Tensile Method of Thin Film Fracture Toughness(51671153)")to conduct in-depth research on the method,establish a test model based on mechanical analysis,and realize the standardization of test samples and test process;Combined with the actual test of Cu Zr amorphous alloy film,the test method was systematically evaluated.The specific results are as follows:(1)The preparation of the zigzag back groove structure of the compact tensile sample of the single crystal silicon substrate and the formation of the gradient crack morphology during the unilateral three-point bending process,and the stability of the substrate crack during the tensile test are studied.The promotion of state expansion was analyzed mechanically,which laid the foundation for the tensile test of the microbridge film sample on the substrate surface.(2)The basic characteristics of matrix crack opening displacement under the existence of crack arrest holes are studied,and the concept of virtual crack tip is proposed based on the linear model.Experimental tests show that when the opening of the substrate crack tail is10-35?m,the position of the virtual crack tip O point is almost unchanged,which greatly simplifies the actual test and calculation model of the film tensile strain.(3)The uniaxial tensile model of the film was revised,and the test error caused by the non-uniform uniaxial tensile stress was determined to be 0.2-2.7%;the standardized table for calculating the test results and the Weibull model of fracture toughness were established Statistical analysis;two representative samples of Cu Zr amorphous alloy film were tested in parallel,the fracture toughness was 1.34 and 1.43MPa·m^1/2,and the test accuracy was about0.1MPa·m^1/2.(4)The microstructure study and fracture toughness test results of Cu Zr amorphous alloy film show that with the increase of thickness of Cu Zr amorphous alloy film,its microstructure,hardness,elastic modulus,residual stress,etc.basically unchanged,but fracture toughness The test results of the film have a gradually increasing trend;this size dependence of the fracture toughness of the film may be related to its plane stress state.(5)A large number of tests on the fracture toughness of the Cu Zr amorphous alloy film show that the measured value of the fracture toughness increases with the increase of the length of the film pre-crack,indicating that the film fracture toughness is not a fixed material under plane stress.parameter.