连续冷却条件下半固态7075铝合金的流变性能

摘要

The apparent viscosity and its affecting factors of the semi-solid slurry of 7075 alloy were studied through a Couette-type viscometer during continuously cooling process. The differential scanning calorimetry (DSC) was performed to examine the solid fraction at different temperature. The results show that the apparent viscosity (ηaγ) of the slurry increases with the increase of cooling rate (v) when shearing rate ( ) is identical, while it decreases with the increase of shearing rate when cooling rate is identical. The empirical equation that shows the effect of cooling rate, solid fraction (f s γ) and shear rate on the apparent viscosity is fitted as follows: at =61.235 s-1ηa =(0.21+0.18v)exp(3.99 fs);at v=4℃/min, ηa =2.23exp(3.87γ)exp(-0.01fs). It provides a model for the simulation of semi-solid 7075 aluminum processing.%通过差示扫描量热法确定半固态7075铝合金温度与固相分数的关系，采用Couette型同轴双筒流变仪研究连续冷却状态下半固态7075铝合金浆料的表观黏度及其影响因素。结果表明：在连续冷却条件下，当剪切速率(γ)不变时，冷却速率(v)越大，半固态7075铝合金浆料的表观黏度(ηa )越大；当冷却速率一定时，剪切速率越大，相同温度时半固态7075铝合金浆料的表观黏度越小。对半固态7075铝合金浆料的表观黏度与冷却速率、剪切速率及固相分数(f s )的关系进行数值拟合，为半固态7075铝合金成形的计算机模拟提供了依据：当剪切速率=61.235 s-1时，ηa =(0.21+0.18v)exp(3.99 fs)；当冷却速率v=4℃/min时，ηa =2.23exp(3.87γ)exp(-0.01fs)。γ