Study On Isothermal Drawing Process Of Columnar Crystal Cu-Al-Be Superelastic Alloy Wires

Cu-AI-Be alloy which is casted by OCC process has the columnar crystal structure. It had eliminated the traditional polycrystalline material brittleness of equiaxed crystal boundaries with stress concentration, and it demonstrates excellent mechanical properties and memory performance. Memory alloy in practical applications often require subsequent plastic deformation, but general plastic processing will make it generate strain-induced martensite. If use the heat-treatment to eliminate the martensite, will make it recrystallized, columnar crystal transformed into equiaxed crystal, mechanical properties and memory performance deteriorated. Now, there are some studies on shape memory alloy plastic deformation at home and abroad. They used the isothermal deformation process, heating the workpiece and deformation tools in the same time, can produce the alloy which is neither strain induced martensite and equiaxed crystal under certain temperature conditions and the amount of deformation. So, this paper based on some of the conclusions of the previous, further to do the isothermal drawing experiment, for the data can make Cu-Al-Be alloy use in Industry.This paper prepared columnar crystal Cu-Al-Be alloy wires of φ1.4mm is castcd by OCC process. Let these alloy wires do isothermal drawing experiment under different temperature, different drawing speeds, different extending. Deformed sample is placed under the microscope to observe and analyze the deformation organizations. Specimens were done fatigue bending test, measured the specimen fatigue fracture times, and observed the morphology of the fracture in the scanning electron microscope. Specimens were done the cyclic tensile tests, made the test data to convert into a stress-strain curve. In order to analyze the impact of different process parameters on the microstructure and mechanical properties of Cu-Al-Be super-elastic alloy wires.The result showed that:The columnar crystal Cu-Al-Be super-elastic alloy isothermal drawing with10%and17%elongation, with different deformation temperature, the specimens were appear the necking. The wires isothermal drawing with6%elongation, the specimens appear the necking only with deformation temperature530"C and550"C. The isothermal drawing experiment in the same drawing speed, when the deformation temperature less than470℃, the specimen generated a large amount of martensite, when the deformation temperature more than470℃. the specimen separated out γ2phase. The isothermal drawing experiment in the same deformation temperature, when the drawing speed less than2500mm/min, the specimens generated much martensite. when the drawing speed more the2500mm/min, the specimen separated out Y2phase. The specimens fatigue fracture times first increased and then reduced with the deformation temperature and drawing speed increased. The martensite and the γ2phase both affect the specimen elongation, but the martensite more obvious. With small variable unloading, the specimens almost no residual strain. With30%variable unloading, the specimens generated2%-10%residual strain.