Change of Growth Modes and Calculation of Transform Point on Mg<sub>2</sub>Si in Al Alloys under the Different Cooling Rates

Qin Qingdong; Li Wei; Zhao Yuguang

doi:10.15980/j.tzzz.2015.11.002

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Change of Growth Modes and Calculation of Transform Point on Mg₂Si in Al Alloys under the Different Cooling Rates
Vol. 35, Issue 11, Pages: 1125-1129(2015)
Published： 2015 ，
DOI： 10.15980/j.tzzz.2015.11.002

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[1]秦庆东,李伟,赵宇光.不同冷速下Mg_2Si生长方式的转变及转换点计算[J].特种铸造及有色合金,2015,35(11):1125-1129.

Qin Qingdong, Li Wei, Zhao Yuguang. Change of Growth Modes and Calculation of Transform Point on Mg₂Si in Al Alloys under the Different Cooling Rates. [J]. Special Casting & Nonferrous Alloys 35(11):1125-1129(2015)
[1]秦庆东,李伟,赵宇光.不同冷速下Mg_2Si生长方式的转变及转换点计算[J].特种铸造及有色合金,2015,35(11):1125-1129. DOI： 10.15980/j.tzzz.2015.11.002.

Qin Qingdong, Li Wei, Zhao Yuguang. Change of Growth Modes and Calculation of Transform Point on Mg₂Si in Al Alloys under the Different Cooling Rates. [J]. Special Casting & Nonferrous Alloys 35(11):1125-1129(2015) DOI： 10.15980/j.tzzz.2015.11.002.

摘要

研究了不同冷却速度下铝合金熔体中Mg2Si的生长特征。结果发现

在常规凝固条件下

当凝固速度较慢时初生Mg2Si呈现为等轴晶;随着凝固速度增加

由等轴晶转变为树枝晶

晶体尺寸有所减小

但是树枝晶明显变长;进一步增加常规条件下的凝固速度

初生Mg2Si相尺寸更加细小

但是树枝晶的长度仍然超过了200μm

并以小平面的方式生长。在大过冷度和大冷却速率的条件下

Mg2Si相生长方式却发生了转变

由小平面生长转变为非小平面生长。经过计算

发现临界转换的冷却速率为1.169×106℃/s。

Abstract

The growth charicteristics of Mg2 Si in Al melts was described under varied cooling rates.The results show that Mg2 Si particles present equiaxed grain at the lower cooling rate.With the increase of cooling rate

the primary grain is transformed into dendrite with a refined size

however

the size along to dendrites’ direction becomes a longer.With the cooling rate further increase

the size of primary phase becomes the finer

while the length of dendrites’ direction still exceed 200μm with growth in form of facet.However

under the super-cooling degree and super cooling rate condition

the growth modes of primary Mg2 Si in Al melts is changed from facet to non-facet.The calculation results show that the critical cooling rate of growth manner transforming is 1.169×106℃/s.