Al-5%Fe-xNi合金的组织演变与热学性能

Microstructure evolution and thermal properties of Al-5%Fe-xNi alloys

通过传统铸造法制备Al-5%Fe-xNi(x=0%,1.5%,5%,7.5%,10%,质量分数,下同)合金,观察Ni加入后合金中初生相的形态和尺寸变化,分析合金凝固过程的转变情况以及Ni加入对初生相和共晶组织的影响,探讨Ni含量对合金组织及热学性能的影响。结果表明:随着Ni含量的增加,合金中的初生相由不规则块状转变为针状。当Ni含量超过5%时,共晶组织减少,初生相转变为规则排列的Al_(9)FeNi相。Ni的加入显著改变合金的凝固过程,使得初生相析出反应由L→Al_(13)Fe_(4)转变为L→Al_(9)FeNi或L+Al13Fe4→Al9FeNi,共晶析出反应由L→α-Al+Al_(13)Fe_(4)逐渐转变为L+Al_(13)Fe_(4)→α-Al+Al9FeNi和L→Al3Ni+α-Al+Al9FeNi。随着Ni含量的增加,析出相体积分数增大,合金的热导率和热膨胀系数随之降低,热膨胀系数从Al-5%Fe的19.9×10^(-6)K^(-1)(@25~200℃)降至Al-5%Fe-10%Ni的17.6×10^(-6)K^(-1)(@25~200℃)。采用通用有效介质理论(GEMT)模型和修正的Turner模型分别对合金的热导率和热膨胀系数进行预测,发现模拟值与实验值吻合较好。

Al-5%Fe-xNi alloys(x=0%,1.5%,5%,7.5%,10%,mass fraction,the same below)were prepared by the traditional casting method,and the morphology and size changes of the primary phase in the alloys after Ni addition were observed.The transformation of the solidification process of the alloys and the effect of Ni addition on the primary phase and eutectic structure were analyzed,and the influence of Ni content on the microstructure and thermal properties of the alloys was discussed.The results show that with the increase of Ni content,the primary phase changes from irregular bulk to needle-like.As the Ni content exceeds 5%,the eutectic structure decreases,and the primary phase changes to a regularly arranged Al9FeNi phase.The addition of Ni significantly changes the solidification process of the alloys,resulting in the precipitation reaction of the primary phase from L→Al_(13)Fe_(4)to L→Al_(9)FeNi or L+Al_(13)Fe_(4)→Al_(9)FeNi,and the eutectic precipitation reaction from L→α-Al+Al_(13)Fe_(4)to L+Al_(13)Fe_(4)→α-Al+Al_(9)FeNi and L→Al_(3)Ni+α-Al+Al_(9)FeNi.With the increase of Ni content,the volume fraction of the precipitated phase increases,and the thermal conductivity and thermal expansion coefficient of the alloys decrease.The thermal expansion coefficient of the alloys decreases from 19.9×10^(-6)K^(-1)(@25-200℃)of Al-5%Fe to 17.6×10^(-6)K^(-1)(@25-200℃)of Al-5%Fe-10%Ni.The thermal conductivity and thermal expansion coefficient of the alloys are predicted by using the general effective medium theory(GEMT)model and the modified Turner model,respectively.It is found that the simulated values are in good agreement with the experimental values.