Research On Tensile Mechanical Properties Of Alloy Metal Materials At Special Temperature

Titanium alloy with high strength, high tenacity, good causticity and hot stability, is a structural metal material which is widely used in aircraft industry. TC4 alloys have been widely used in engine fan, compressor disks, blades and some aircraft structural parts.The tensile test of TC4 alloy was carried out at room temperature and high temperature(200?400?600?800?1000?C) with Instron5892 tensile machine and Vic-3D(Video image correlate-3D) machine, we could get the tensile properties, and using a Matsuzawa MMT-X durometer test the hardness performance. The microstructure and phase composition at different temperatures test was discussed with the aids of Zeiss optical microscope(OM) and XRD test. Fracture surface analysis by SEM researched the effect of materials failure under different temperatures and drawing speeds. And it discussed the fracture mechanism of TC4 alloy at high temperature.When the drawing speed was 0.5mm/min, the tensile temperature were room temperature and high temperature(200?C, 400?C, 600?C, 800?C and 1000?C), the tensile experimental results showed that with temperature increasing, the tensile strength and yield strength of TC4 alloy decreased; the elongation increased firstly, and then decreased; the hardness increased firstly then decreased and increased finally The tensile strength of TC4 alloy decreased from 799.9MPa to 15.1MPa, and the yield strength decreased from 731.2MPa to 12.4MPa. The maximum elongation was 332% at 800?C. By the metallographic and XRD analysis, the volume of the first ?-phase declined with the tensile temperature increasing, the size of ? phase increased, and then ? phase converted to ? phase at 1000?C. The results of SEM showed that as the temperature increases, ductile fracture characteristics gradually increased, and the brittle fracture characteristics gradually reducing. At 800?C, the brittle fracture characteristics disappeared, it implied that the tensile fracture of the alloys occurred in a ductile mode.When the tensile temperature is 400?C, and the drawing speed are 0.1mm/min, 0.5 mm/min, 1 mm/min, 2 mm/min and 4 mm/min, the tensile experimental results show that with the tensile speed increasing, the tensile strength and yield strength of TC4 alloy increased, and the tensile strength of TC4 alloy d from 621.9MPa to 659.7MPa, and the yield strength increased from 495.1MPa to 529.1MPa. The elongation increased firstly, and then decreased. The maximum elongation was about 22% at the drawing speed of 0.5mm/min. The results of SEM showed that lots of dimples and small cleavage planes could be observed on the fracture surfaces. The fracture mechanism was between ductile fracture and brittle fracture. With the increasing of the drawing speed, the brittle fracture characteristics increased, and the ability to resist plastic deformation of the material increased.