连铸速度对CUALNI记忆合金晶粒长大及弯曲疲劳的影响

Effects of Drawing Velocity on Grain Growth and Bending Fatigue of CuAlNi Shape Memory Alloy with Column Crystal in Heat Mould Continuous Casting

以4种速度连铸了柱状晶组织的CUALNI记忆合金丝并热处理,检验其晶粒长大及弯曲疲劳性能。连铸速度大于240MM/MIN,Γ2相的析出被抑制;速度达480MM/MIN时由于凝固前沿液相受到激冷而形成等轴晶。360MM/MIN为柱状晶加热长大的临界连铸速度。超过此速度,加热时晶粒将急剧长大。临界连铸速度以下提高连铸速度可细化晶粒,经热处理消除内应力后,弯曲疲劳断裂次数可大幅提高。

Abstract The grain growth and bending fatigue was examined for heat treated CuAlNi shape memory alloy with column crystal in heat mould continuous casting at four kinds of drawing velocity, such as 240mm/min, 360mm/min. 480mm/min. Precipitation of γ2 phase in CuAlNi shape memory alloy can be inhibited at drawing velocity more than 240mm/min, and increased to 480mm/min, the equiaxed crystal is formed in the alloy due to chilling effects acted on melt front during solidification. The critical drawing velocity during column crystal growth is observed at 360mm/min, and more than the velocity, the grain is sharply grown while less than the velocity, the grain size can be refined with increase in drawing velocity, where bending fatigue can be considerably improved by heat treatment eliminating the internal stress.