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Effect of cooling rate on microstructure and microhardness of hypereutectic Al–Ni alloy
Archives of Civil and Mechanical Engineering ( IF 4.4 ) Pub Date : 2021-01-12 , DOI: 10.1007/s43452-020-00159-2
A. P. Carrara , R. Kakitani , A. Garcia , N. Cheung

High solidification cooling rates during unsteady-state conditions of solidification of Al-based alloys can induce different microstructural length scales or metastable phases, leading to improved properties. The present study aims to characterize the microstructural arrangement of the hypereutectic Al–8 wt%Ni alloy, unidirectionally solidified in unsteady-state heat flow conditions, examining the influence of the cooling rate in the development of the Al–Al3Ni eutectic and the primary phase. A columnar-to-equiaxed macrostructural transition is shown to occur at a solidification cooling rate () of about 4.8 °C/s, with different microstructures associated with each morphological zone. The observation of microstructures of hypoeutectic, eutectic and hypereutectic Al–Ni alloys, has permitted an asymmetric coupled zone diagram to be proposed. The microstructural interphase spacings of the Al–8 wt%Ni alloy are experimentally determined and correlated to , and the Vickers microhardness (HV) is shown to decrease with the increase in such spacings. The higher experimental HV profile of the examined hypereutectic alloy as compared to that of the eutectic Al–Ni alloy is attributed to the formation of a supersaturated solid solution of Ni in α-Al.



中文翻译:

冷却速度对过共晶Al-Ni合金组织和显微硬度的影响

在铝基合金凝固的非稳态条件下,较高的凝固冷却速率会引起不同的显微组织长度尺度或亚稳相,从而改善性能。本研究旨在表征在非稳态热流条件下单向凝固的过共晶Al–8 wt%Ni合金的微观结构排列,研究冷却速率对Al–Al 3 Ni共晶和合金的发展的影响。初级阶段。的柱状到等轴宏观结构的过渡被示出在凝固冷却速率发生(Ť)的温度约为4.8°C / s,与每个形态区域相关的微观结构不同。对亚共晶,共晶和过共晶Al-Ni合金的微观结构的观察,已经提出了不对称耦合区图。在Al-8重量%的Ni合金的微观结构间距相间实验确定和相关Ť,和显微硬度(HV)被示出以这样的间距的增加降低。与共晶Al-Ni合金相比,所检验的过共晶合金具有更高的实验HV曲线,这归因于Ni在α- Al中形成的过饱和固溶体。

更新日期:2021-01-12
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