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The samples were fabricated by 220 t thixomolded machine made by Japan Steel Works. The microstructure from the AZ91D magnesium alloy chips to the thixomolded products was investigated. Melting behavior of the chips in thixomolding process was analyzed. The evolution processing of solid phase morphology was studied, and evolution model was put forward. The results show that microstructures in outer zone of a chip and the inner zone are obviously different, and the severe distortion takes place in the brim of the chip, where the grains are observed to be bent, distorted, even broken. The severe plastic deformation region is firstly molten, then segregation area in the inner of the chip continues to melt. The liquid phase in solid phase does not formed by liquid entrapped during shearing process, but primarily induced by internal composition segregation. 相似文献
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介绍了镁合金半固态注射成形工艺,阐述了成形温度控制、原料输送与熔融控制、注射速度控制等技术要求。试验研究了镁合金半固态注射成形设备注射速度的控制方法:一是采用高响应高速注射油缸的结构,其中活塞与注射螺杆相连接,通过液压油推动活塞带动螺杆实现高速注射;二是采用注射油缸进油与出油的组合伺服控制,通过高精度压力传感器和位置传感器在线监测注射速度,并进行实时双闭环控制,实现了对注射速度的精确闭环控制。 相似文献
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对高氮奥氏体不锈钢0Cr21Mn17Mo2Nb N0.83进行表面机械压磨处理,重点研究经360 min表面机械压磨后,高氮奥氏体不锈钢表面纳米层的组织结构和在不同加热温度、保温时间条件下,该纳米表面层的热稳定性。结果表明:高氮奥氏体不锈钢0Cr21Mn17Mo2Nb N0.83经360 min表面机械压磨处理后,表面晶粒尺寸达到纳米级别,表面层的硬度较芯部基体增加一倍以上,且由芯部基体到表面的晶粒逐渐细化;机械压磨以及随后的热处理均未造成高氮奥氏体不锈钢表面层单一奥氏体结构的改变,表明该种材料具有良好的结构稳定性;加热温度对高氮奥氏体不锈钢0Cr21Mn17Mo2NbN0.83表面纳米层及过渡层的组织稳定性起决定作用,而保温时间对其影响不大。 相似文献
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研究了Co基自熔合金、Ni基自熔合金 WC、Co基自熔合金 WC激光熔覆层在不同温度下的显微组织和各种化合物的硬度 ,结果表明三种材料在相同激光熔覆工艺参数下获得的熔覆层的高温显微组织、性能存在很大的差异。Ni基自熔合金 WC在 70 0℃时硬度开始显著降低且显微组织发生很大变化 ,而Co基自熔合金和Co基自熔合金 WC在 70 0℃时才开始发生变化且变化幅度较小。同时证明WC在加热过程中硬度没有显著降低。试验结果对获得具有抗高温粘着磨损的激光熔覆层有重要的理论和实际意义。 相似文献
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Mold filling in lately-developed Thixomolding process is a complex process, of which numerical simulation is necessary for development. Governing equations and numerical models are first given, and then the experiment and its filling simulation are carried out. The results demonstrate that the modeling temperature changes from 864 to 873 K when the barrel temperature is 873 K. The difference is primarily in the runner system, but nearly invariable in the part. Consequently, the slurry fills the cavity smoothly with low solid fraction, and the filling process finishes in 5 ms, the filling process completes successfully before solidification of the slurry, which has good agreement with the experiment. Through a snapshot of the filling process and defects tracking, drawbacks are displayed and confirmed in the experiment. 相似文献