连续冷却条件下半固态7075铝合金的流变性能

Rheological behavior of semi-solid 7075 aluminum alloy in continuously cooling process

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()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(fs)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(3.99fs);当冷却速率v=4℃/min时,ηa=2.23exp(3.87)exp(-0.01fs)。

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（ηa） 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（fs） and shear rate on the apparent viscosity is fitted as follows： at =61.235 s-1,ηa=（0.21＋0.18v）exp（3.99fs）; at v=4 ℃/min,ηa=2.23exp（3.87）exp（-0.01fs）. It provides a model for the simulation of semi-solid 7075 aluminum processing.