SiC_w/Al composite was fabricated through a squeeze cast route and coldrolled to about 30 percent, 50 percent and 70 percent reduction In thickness, respectively. Thelength of whiskers in the composite before and afte...SiC_w/Al composite was fabricated through a squeeze cast route and coldrolled to about 30 percent, 50 percent and 70 percent reduction In thickness, respectively. Thelength of whiskers in the composite before and after rolling was examined using SEM. Some of therolled composites were recrystallization annealed to remove the work hardening of matrix alloy. Thetensile strength of the rolled and annealed SiC_w/Al composites was examined and then associatedwith the change of the whisker length and the work hardening of matrix alloy. It was found that thetensile strength is a function of the degree of cold rolling. For the cold rolled composites, withthe increase in the degree of cold rolling, the tensile strength increases at first, and decreaseswhen the degree of cold rolling exceeds 50 percent. For the annealed ones, however; the tensilestrength decreases monotonously with the increase in rolling degree. The different changes intensile strength between the rolled and annealed composites could be attributed to the result of thecompetition between the work hardening of matrix resulting from the cold rolling and the worksoftening arising from the change of whisker length.展开更多
A 15 vol. pct SiC_w/Al composite was fabricated by a squeeze cast route followed by hot extrusion in the extrusion ratioof 18:1 and cold rolling to 50%. Microstructural evolution in the cold rolled composite during an...A 15 vol. pct SiC_w/Al composite was fabricated by a squeeze cast route followed by hot extrusion in the extrusion ratioof 18:1 and cold rolling to 50%. Microstructural evolution in the cold rolled composite during annealing was studied usingmacrohardness measurement and transmission electron microscopy (TEM). It was found that, during cold rolling the plastic flowof the matrix was restricted by the whiskers around them along the rolling direction, which resulted in different microstructurefrom near whiskers to far away. The cold rolled composite exhibited different microstructural development on 1 h annealingat different temperatures. Under annealing at about 100℃, recovery reaction occurred obviously and the introduction ofSiC whiskers resulted in enhanced recovery reaction. Under annealing above about 200℃, recrystallization (growth of nucleiby high-angle grain boundary migration) and extended recovery took place simultaneously. When annealing temperaturewas increased up to 500℃, recrystallization fully took place in the cold rolled microstructure. The starting temperature ofrecrystallization was about 200℃. Whiskers played a role in stimulating the nucleation of recrystallization.展开更多
基金This work is financially supported by the National Natural Science Foundation if China(No.50071031)
文摘SiC_w/Al composite was fabricated through a squeeze cast route and coldrolled to about 30 percent, 50 percent and 70 percent reduction In thickness, respectively. Thelength of whiskers in the composite before and after rolling was examined using SEM. Some of therolled composites were recrystallization annealed to remove the work hardening of matrix alloy. Thetensile strength of the rolled and annealed SiC_w/Al composites was examined and then associatedwith the change of the whisker length and the work hardening of matrix alloy. It was found that thetensile strength is a function of the degree of cold rolling. For the cold rolled composites, withthe increase in the degree of cold rolling, the tensile strength increases at first, and decreaseswhen the degree of cold rolling exceeds 50 percent. For the annealed ones, however; the tensilestrength decreases monotonously with the increase in rolling degree. The different changes intensile strength between the rolled and annealed composites could be attributed to the result of thecompetition between the work hardening of matrix resulting from the cold rolling and the worksoftening arising from the change of whisker length.
基金This work is financially supported by the National Natural Science Foundation of China under grant No.50071031.
文摘A 15 vol. pct SiC_w/Al composite was fabricated by a squeeze cast route followed by hot extrusion in the extrusion ratioof 18:1 and cold rolling to 50%. Microstructural evolution in the cold rolled composite during annealing was studied usingmacrohardness measurement and transmission electron microscopy (TEM). It was found that, during cold rolling the plastic flowof the matrix was restricted by the whiskers around them along the rolling direction, which resulted in different microstructurefrom near whiskers to far away. The cold rolled composite exhibited different microstructural development on 1 h annealingat different temperatures. Under annealing at about 100℃, recovery reaction occurred obviously and the introduction ofSiC whiskers resulted in enhanced recovery reaction. Under annealing above about 200℃, recrystallization (growth of nucleiby high-angle grain boundary migration) and extended recovery took place simultaneously. When annealing temperaturewas increased up to 500℃, recrystallization fully took place in the cold rolled microstructure. The starting temperature ofrecrystallization was about 200℃. Whiskers played a role in stimulating the nucleation of recrystallization.
