半固态LC4合金的屈服应力

以SIMA法制备的非枝晶LC4合金为例 ,进行压缩试验 ,测出了应变速率、变形温度及保温时间不同时的屈服应力。结果表明 :当应变速率相同时 ,在固态区 ,屈服应力随着变形温度的增加稍有减小 ;而在半固态区 ,屈服应力随着变形温度的提高明显减小 ,且在共晶点附近急剧下降。屈服应力随着保温时间增加而略有减小的主要原因是由于随着保温时间的增加 ,晶粒的尺寸、球形化程度、固相晶粒间的结合程度及晶粒内俘获的液体不同所致。当变形温度及保温时间相同时 ,随着应变速率的升高 ,屈服应力明显增加。通过分析不同变形温度及保温时间的材料显微组织进化规律 ,阐明了屈服应力与显微组织之间的内在联系

Yield stress of LC4 alloy in semi-solid state

Extensive compression experiments were conducted to measure yield stress under different strain rates, deformation temperatures and holding times. Non dendritic LC 4 alloy fabricated by SIMA method was used. The results of yield stress measurements in a constant strain rate were presented. Yield stress value decreases slightly with the increasing of temperature in solid state, whereas yield stress value decreases dramatically with the increasing of temperature in semi solid state. A sharp drop of yield stress was found to occur at eutectic point. Grain size, spheroidization, cohesion between solid grains and entrapped liquid inside grains are different with the increasing of holding time, which results in a decrease of yield stress. The results of yield stress measurements at a constant temperature and holding time were also presented. The yield stress value increases dramatically with the increasing of strain rate. In addition, microstructure evolutions at different temperatures and holding time are analyzed. Inherent relationship between yield stress and microstructure is clarified.