先进复合材料工艺理论基础-凝固

1、先进复合材料工艺理论基础 -凝固,主讲人：范清松 导师 ：陈善华(教授),提 纲,引言 浸渗凝固过程温度场 凝固组织,引 言,复合材料凝固的重要性： 凝固，是物质从液相变为固相的相变过程，是产生晶核和晶核生长的过程。 液相工艺最后一个环节； 不仅影响浸渗过程，而且决定最终显微组织； 对复合材料性能影响很大。,引 言,复合材料凝固涉及的问题： 凝固过程温度场； 凝固组织； 凝固对性能影响,凝固过程温度场 短纤维复合材料,实验条件： gas pressure infiltration：3 MPa using oxygen free nitrogen gas ； 0.16 volume fracti

2、on short SAFFIL fibre preforms ； commercial purity aluminium ； temperature from four points within the die, three within the reinforcement preform and one within the non-infiltrated melt,浸渗过程温度场,Temperature record during casting for (a) CP1 (b), CP2 and (c) CP3 each cast with a fibre volume fraction

3、 of 0.16 and an initial fibre temperature of 450 C, initial melt temperatures where 820, 775 and 675 C, respectively,positions are as depths below the top surface of the preform,凝固过程温度场,Casting conditions of samples CP1, CP2 and CP3,凝固过程温度场,Temperature record of the solidification of casting CP1,凝固过

4、程温度场,Axisymmetric section of casting CP1 (1.2) etched in Tuckers reagent. The white dashed line indicates the axis of symmetry and the white arrows the top of the preform,浸渗过程温度场 模拟,the fibres initially at 450 C, 0.2 volume fraction exposed to melt at a 100 C superheat, 760 C. the temperature equili

5、brates very rapidly, 106 s due to the fine scale of the fibre,浸渗过程温度场 模拟,Theoretical 3D plot of temperature against time and position within the casting,sample CP1. Temperature is plotted against both time and position within the final casting, a positive depth refers to the composite section of the

6、 casting while a negative depth infers a position within the non-infiltrated excess melt above the reinforced section,浸渗过程温度场 模拟,Theoretically calculated temperature plot for castings CP1, CP2 and CP3,凝固过程温度场 模拟,高导热材料和电子封装材料,HTCM Group,3D temperature/time/depth plot for the solidification of casting

7、 CP1,凝固过程温度场 模拟,Theoretical plot for the solidification of casting CP1,凝固过程温度场 颗粒复合材料,Ternary equilibrium diagram Al-Mg-Si,凝固过程温度场 颗粒复合材料,Scheme of the stand for ATD measurements ATD method (analysis of thermal derivative dT/dt ）,凝固过程温度场 颗粒复合材料,Solidification of the AlSi7Mg4 composite matrix: (a) AT

8、D curve, (b) heat source function calculated from the ATD curve (dT/dt); AB-dynamic of solidification of the -phase, CD-dynamic of the eutectic solidification, AC- phase solidification time, CE-eutectic solidification time, AE-composite solidification time, (dT/dt)g-basic (calorimetric) curve,凝固过程温度

9、场 颗粒复合材料,The thermophysical properties of the materials,凝固过程温度场 颗粒复合材料,Influence of the SiC particle content on the kinetics of solidification of the AlSi7Mg4-SiC composites,The ceramic particles introduced into the metal matrix change significantly the kinetics of the composite solidification, decr

10、easing the mass of the solidifying metal by the quantity corresponding to the volume occupied by the SiC particles, and by diminishing the quantity of liberated solidification heat, increasing the heat flow resistance caused by the presence of the particles (SiC Al).,凝固过程温度场 颗粒复合材料,Influence of the

11、SiC particle size on the kinetics of solidification of the AlSi7Mg4-SiC composites,Taking into account the registered course of the cooling curve and its first derivative dT/dt the following points can be determined:,凝固过程温度场 颗粒复合材料,The characteristic points of solidification,凝固组织,Back scattered elec

12、tron image of iron-rich precipitates in casting CP3 taken behind the position of the remelting front at the end of infiltration, i.e. from a region solidifying from a purely liquid matrix,凝固组织,Back scattered electron image of iron rich impurity precipitates in CP1 from below the final position of th

13、e remelting front where solid material formed during infiltration was present prior to final solidification,凝固组织,Microstructures of (a) the metal matrix and (b) the AlSi7Mg4-SiCp composite (20%).,SiC particles retard the growth of the phase,凝固组织,SEM microstructure of the SiCp/matrix interface in the AlSi7Mg4-SiCp composite,The lack of the Al4C3 phase has been also confirmed by electron microscopy,凝固组织,The influence of (a) content and (b) size of SiC particle on the liquidus temperature in AlSi7Mg4-S