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2 results about "Intergranular fracture" patented technology
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In certain materials and under certain conditions, the boundaries between the grains are the weakest regions in the material. An intergranular fracture is a type of fracture in which the crack propagates along the grain boundaries of the material, usually when these grain boundaries are weakened. Intergranular fracture is to be distinguished from the more commonly seen transgranular fracture, where the crack grows through the material grains rather than at the grain boundaries. Though less frequently observed, intergranular cracking is likely to occur if there is a hostile environmental influence and is favored by larger grain sizes and higher stresses. Intergranular cracking is possible at a wide range of temperatures. While transgranular cracking is favored by strain localization (which in turn is encouraged by smaller grain sizes), intergranular fracture is promoted by strain homogenization resulting from coarse grains.
Preparation process of medical fine-grained nickel-titanium shape memory alloy rod
This disclosure provides a process for preparing fine-grained nickel-titanium shape memory alloy rods for medical use, comprising: forging a heated nickel-titanium alloy ingot through multiple passes, performing multiple high-temperature continuous rolling passes, and then performing thermomechanical treatment to obtain fine-grained nickel-titanium shape memory alloy rods. This invention, through a combination of specific multi-pass forging and strictly temperature-controlled high-temperature continuous rolling, utilizes a robust dynamic recrystallization mechanism to fundamentally refine and homogenize the austenitic matrix grains, and completely breaks down the continuous brittle Ti2Ni phase distributed along the grain boundaries into a randomly dispersed distribution, thereby obtaining fine-grained nickel-titanium alloy rods with high purity and excellent microstructure. This solves the practical problems caused by the coarse grains and brittle phase segregation of the original cast nickel-titanium alloy, such as easy intergranular fracture, difficult processing and forming, low yield, and poor fatigue life in medical applications.
Owner:NORTHWESTERN POLYTECHNICAL UNIV
Method and system for controlled opening of cracks in metal components based on fatigue guidance and real-time monitoring
This invention discloses a method and system for controllable crack propagation in metal components based on fatigue guidance and real-time monitoring, belonging to the technical fields of metal material failure analysis, non-destructive testing, and structural safety assessment. Through fatigue-guided propagation, the crack separates slowly and stably at extremely low stress levels, avoiding macroscopic plastic deformation, impact damage, and instantaneous fracture zone impact caused by traditional overload fracture, perfectly preserving the original microstructures such as fatigue striations, cleavage planes, and intergranular fracture. By deploying monitoring sensors and using a crack state fusion solution model based on real-time data acquisition, the crack propagation rate is dynamically calculated, thereby adjusting the parameters of high-frequency, low-amplitude cyclic loading. This closed-loop feedback control mechanism can perceive the crack state in real time, ensuring stable crack propagation under fatigue mechanisms, creating a core condition for obtaining high-quality fracture morphology.
Owner:XIAN THERMAL POWER RES INST CO LTD