Hot Rolling Process Of Columnar Crystal Cuaibe Superelastic Alloy

Superelastic Cu-Al-Be shape memory alloy wires is casted by OCC process with columnar crystal structure. Which eliminated the traditional polycrystalline material brittleness of equiaxcrystal boundaries with stress concentration. The wires obtained excellent mechanical properties and memory performance. The OCC process allows the wires to obtain precise size and near net shape, so it was used in some field.The OCC process can not obtain the silk with less than lmm and easily bend and complex section,so the wires require to plastic processing in high temperature. Stress of the plastic processing will lead to parent phase to martensite, residual martensite will make the wire lose superelastic. Heat treatment can make martensite reverted parent phase, while stress come from phase transition and temperature changes in deformation, heating again will appear recrystallization phenomenon.Columnar crystal Cu-Al-Be alloy of8mm×2.5mm (wide×thick) and Φ1.5mm are casted by OCC process. Superelastic of strip Cu-Al-Be is compressed by different deformation temperature and deformation rate and small deformation. Analysis of the strip wire through XRD diffraction. The strip is heated again after deformation for finding critical temperature of static recrystallization. For measuring the influence of residual stress with holding time, the strip is measured by drilling method The deformation temperature is influenced the content of precipitate. The alloy wire of Φ1.5mm is processed by hot-rolled device which is designed by myself. Then bending fatigue and tensile performance is determined. To analysis the different deformation influence on the structure of Cu-Al-Be superelastic alloy wires.The result shows that:The wires are not occur dynamic recrystallization below450℃. Between450℃to550℃, along with the deformation temperature reduction or deformation rate increase, deformation increase gradually with dynamic recrystallization happen, and the best deforming temperature is450-500℃. Critical temperature of static recrystallization is610℃under deformation less than20%. The content of precipitate gradually increasing with the increase of temperature deformation before the dynamic recrystallization happened. The content of precipitate with the recrystallization fully and reduce once dynamic recrystallization happened. The content of precipitate increasing with deformation temperature and deformation when Static recrystallization happened. Holding more time will reduce residual stress below500℃. Instead, Rapid Cooling will reduce residual stress more than500℃. The alloy can keep good elongation rate at the hot rolling temperature of480℃. fatigue times first increases and then decreases with the increase of temperature between440℃to520℃, the highest time of bend fatigue is hot rolling temperature of480℃, as high as53600. The higher the deformation temperature, the easier to form γ2.