Effects of pouring temperature on the cooling rules of alloy melts and the semi-solid microstructure
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摘要: 介紹了一種實驗室自主研發的輕合金半固態漿料制備設備——錐桶式流變成形機(TBR),該設備利用刻有凸紋和溝槽的內、外錐桶的相對轉動,使合金熔體在凝固過程中受到劇烈的剪切攪拌,從而獲得合金半固態漿料.對TBR工藝的傳熱模型進行了推導,以A356為實驗材料得出制備的A356鋁合金半固態漿料溫度與澆注溫度的關系式,同時分析了不同澆注溫度下合金熔體的冷卻規律和獲得的半固態組織形貌.結果表明,適當降低A356合金熔體的澆注溫度可以延長初生固相受到的剪切時間和增加剪切次數,從而獲得細小、均勻的半固態組織.當澆注溫度為640℃時,初生固相平均晶粒尺寸為68μm,形狀因子為0.82.Abstract: A self-developed taper barrel rheomoulding(TBR) machine for preparing light alloy semi-solid slurries was introduced.Relative rotation of the internal and external taper barrel whose surface contains wales and grooves led to an intense shearing turbulence of alloy melts during solidification,and then the semi-solid slurries were prepared.A heat transmission model of TBR process was deduced.Taking A365 aluminum alloy as an experimental material,the related formula between slurry temperature(Tout) and pouring temperature(Tp) of the alloy was obtained.The cooling rules of the alloy melt and the semi-solid microstructure at different pouring temperatures were analyzed.The results show that properly decreasing the pouring temperature of A365 alloy melt can increase the shearing time and shearing frequency for the primary solid phase,thereby obtaining a fine and homogeneous semi-solid microstructure.When the pouring temperature is 640℃,the average grain size of primary particles is 68μm and the shape factor is 0.82.
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Key words:
- aluminum alloys /
- semi-solid slurry /
- solidification /
- microstructure
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