(西安理工大學(xué) 材料科學(xué)與工程學(xué)院， 西安 710048)
摘 要: 研究快速凝固Cu-20%Sn亞包晶合金的相結(jié)構(gòu)、 晶體生長行為和組織特征，分析冷卻速率與組織形成之間的相關(guān)規(guī)律。 結(jié)果表明： 在急冷快速凝固條件下， 合金的包晶轉(zhuǎn)變和共析轉(zhuǎn)變均受到抑制， 形成了以亞穩(wěn)的Cu5.6Sn金屬間化合物為主相的快速凝固組織； 隨著冷卻速率的增大， α-Cu相含量減少， Cu5.6Sn相數(shù)量顯著增多； 晶體生長的方向性增強(qiáng)； Cu5.6Sn生長方式由小平面向非小平面生長轉(zhuǎn)變， 組織形態(tài)由粗大板條狀向細(xì)密柱狀轉(zhuǎn)變。 TEM分析表明： 在Cu5.6Sn晶內(nèi)存在大量的位錯塞積及孿晶；孿晶之間相互平行， 間距約25~80 nm； 隨冷卻速率的增大， 位錯密度增大， 孿晶數(shù)量增多。
關(guān)鍵字: Cu-Sn合金； 快速凝固； 晶體生長； 相結(jié)構(gòu)；位錯
（School of Materials Science and Engineering,
Xi'an University of Technology, Xi'an 710048, China）
Abstract: The phase structure, crystal growth behavior and microstructural characteristics of rapidly solidified Cu-20%Sn alloy were investigated and the relationships between the microstructure formation and the cooling rate were analyzed theoretically. The results show that under rapid solidification condition, the peritectic transition and eutectoid transitions of the alloy are all suppressed, which results in the formation of microstructures characterized mainly by metastable Cu5.6Sn metallic compound. With increasing cooling rate, the amount of α-Cu phase decreases, while that of Cu5.6Sn phase increases. Meanwhile, the growth form transforms from faced to non-faced growth and the microstructure exhibits apparent growth orientation. TEM reveals that there exists large quantity of dislocation pile-up and twins in Cu5.6Sn grains. Those twins are parallel to each other with the interspacing about 25~80 nm, and extend to the boundary of Cu5.6Sn branches. The increase of cooling rate results in the increase of dislocation density and twin quantity.
Key words: Cu-Sn alloy; rapid solidification; crystal growth; phase structure; dislocation
