LC_4合金的显微组织与屈服应力

以SIMA法制备的非枝晶LC4合金为例,进行了大量的压缩试验,测出了变形速率、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少,且在共晶点附近急剧下降。屈服应力随着保温时间的增加略有减小,这主要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。此外,分析了不同变形温度及保温时间的显微结构进化规律,阐明了屈服应力与显微结构之间的内在联系。

Study on Yield Stress of LC_4 Alloy in the Semi-solid State

Extensive compression experiments were conducted to measure yield stress under different strain rates, deformation temperatures and holding times. In this study, non-dendritic LC4 alloy fabricated by SIMA method was used. This paper presents results of yield stress measurements in a constant strain rate. Yield stress value decreases slightly with increasing of temperature in solid state, whereas yield stress value decreases dramatically with increasing of temperature in semi - solid state. A sharp drop in yield stress was found to occur at eutectic point. Grain size, spheroidization, cohesion between solid grains and entrapped liquid inside grains are different with increasing of holding time, these result in a decrease of yield stress. This paper also presents results of yield stress measurements in a constant temperature and holding time. Yield stress value increases dramatically with increasing of strain rate. In addition , microstructure evolution of different temperatures and holding times are analyzed. Inherent relationship between yield stress and microstructure is clarified.