(沈陽工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院，沈陽 110870)
摘 要: 基于修正的Clyne-Davies熱裂模型(CSC*)，對Mg-6Zn-xCu-0.6Zr(x%=0，1%，2%，3%，質(zhì)量分數(shù))合金熱裂傾向性進行預(yù)測；采用雙電偶熱分析法研究Mg-6Zn-xCu-0.6Zr合金凝固路徑、凝固過程中的特征溫度、枝晶干涉固相分數(shù)等。利用“T”型熱裂模具測試系統(tǒng)采集Mg-6Zn-xCu-0.6Zr合金凝固收縮力隨溫度(或時間)的變化曲線。實驗結(jié)果與CSC*預(yù)測值均表明合金的熱裂傾向性隨著Cu含量的增加而減小。Cu元素的加入使初生α-Mg相的析出溫度降低、MgZn2相的析出溫度升高，從而使合金的凝固溫度區(qū)間變窄，降低合金的熱裂傾向性。Mg-6Zn-(0,1)Cu-0.6Zr合金熱裂紋斷口主要為液膜和分離的自由枝晶臂。Mg-6Zn-(2,3)Cu-0.6Zr合金斷口表面生成大量的低熔點共晶相，液膜較厚，增強殘余液相對分離的枝晶補縮能力，降低合金的熱裂傾向性。
關(guān)鍵字: 鎂合金；熱裂傾向性；合金凝固路徑；凝固溫度區(qū)間
（School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110870, China）
Abstract:Hot tearing tendency of Mg-6Zn-xCu-0.6Zr (x%=0, 1%, 2%, 3%, mass fraction) alloys were predicted based on modified Clyne-Davies model (CSC*). The solidification path, characteristic temperature during solidification, the solid fraction in coherent dendrite point of Mg-6Zn-xCu-0.6Zr alloys were studied by the double thermocouples thermal analysis. The curve of solidification contraction stress with temperature (or time) of Mg-6Zn-xCu-0.6Zr alloys were measured using the “T” type hot tearing permanent-mold. The results show that the CSC* prediction values are in good agreement with the experimental results. The hot tearing tendency decreases with increasing Cu content. The precipitation temperature of primary α-Mg phase decreases and the precipitation temperature of MgZn2 phase increases by addition of Cu element, thus shortening the solidification temperature range of alloys and decreasing the hot tearing tendency. The hot cracking fractures of Mg-6Zn- (0,1) Cu-0.6Zr alloys are mainly occupied by the liquid film and separated free dendrite arm. A large number of eutectic phase with low melting point and the thicker liquid film were observed on the fracture surfaces of Mg-6Zn- (2,3) Cu-0.6Zr alloys which enhances the feeding ability and reduces the hot tearing tendency.
Key words: Mg alloy; hot tearing tendency; solidification path; solidification temperature range
