Mechanical stir casting of aluminium alloys from the mushy state: process, microstructure and mechanical properties
Mechanical stir casting of aluminium alloys from the mushy state: process, microstructure and mechanical properties
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DOI：
10.1016/s0921-5093(01)01832-9
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发表时间：
2002-03
期刊：
影响因子：
6.4
通讯作者：
D. Brabazon;D. Browne;A. Carr
中科院分区：
文献类型：
--
作者：
D. Brabazon;D. Browne;A. Carr
研究了控制搅拌对铝合金凝固组织和力学性能的影响，并与传统的重力冷铸材料进行了比较。一种新型的装置被用来加工糊状状态的铝合金，该装置包括在管状坩埚中旋转的凹槽反应结合氮化硅棒。搅拌铸造装置是专门设计的，也可以在这种条件下对合金进行流变学研究。采用析因试验设计，研究了剪切速率(γ̇)、剪切时间(Ts)和剪切过程中固相体积分数(F S)等工艺参数对搅拌铸造合金显微组织和静态、动态力学性能的影响。显微组织的研究包括对初生相形态的计算机辅助图像分析。在较低的f_s值时，初生相更加球状，但这并不是力学性能的最佳形态。在所有情况下，与常规铸造和以前的搅拌铸造相比，搅拌铸造条件下的力学性能得到了改善，气孔率也有所减少。然而，与商用电磁搅拌流变铸造的合金相比，后者具有更好的力学性能。建议在需要非常简单和厚壁形状的情况下，考虑将机械搅拌铸造工艺作为重力压铸的替代方案。
A comprehensive study was carried out to establish the effects of controlled stirring during solidification on the microstructure and mechanical properties of aluminium alloys, in comparison to conventionally gravity chill cast material. A novel device comprising a grooved reaction bonded silicon nitride rod rotating in a tube-like crucible was used to process aluminium alloys in the mushy state. The stir casting device was specially designed to also enable rheometric study of the alloys in this condition. A factorial design of experiments was used to determine the effect of the process variables shear rate (γ ̇ ), shear time (ts), and volume fraction solid during shear (fs) on microstructure and both static and dynamic mechanical properties of the stir cast alloy. Investigation of the microstructure consisted of computer-aided image analysis of the primary phase morphology. A more globular primary phase was achieved at low values of fs, but this was not the optimum morphology for mechanical properties. In all cases, improved mechanical properties and reduced porosity were obtained in the stir cast condition in comparison with conventional casting and in comparison with previous work on stir casting. Comparison with alloy commercially rheocast via electromagnetic stirring, however, showed that the latter had superior mechanical properties. It is proposed that the mechanical stir casting process be considered as an alternative to gravity die casting in cases where very simple and thick walled shapes are required.