CAJ | 학술논문

针对单轴压缩实验，根据颗粒增强金属基复合材料中颗粒和基体两相的局部变形协调条件，并通过简单的位错模型，确定出与变形协调相应的几何必需位错密度，进而导出一种颗粒强化-应变梯度律。从中可以清楚地看出，颗粒增强金属基复合材料的强化由材料的微结构特征几何参数l⌒和基体应变梯度联合控制。对于颗粒含量一定的复合材料，颗粒越小，应变梯度越高，强化效果越好。这一结果揭示了，颗粒强化及尺寸效应主要是通过应变梯度效应来表现的。这也同时说明，应变梯度可能是控制材料变形与断裂的重要因素之一。
침대단축압축실험，근거과립증강금속기복합재료중과립화기체량상 적국부변형협조조건，병통과간단적위착모형，학정출여변형협조상응적궤하필수위착밀도 ，진이도출일충과립강화-응변제도률。종중가이청초지간출，과립증강금속기복합재료적 강화유재료적미결구특정궤하삼수l⌒화기체응 변제도련 합공제。대우과립함량일정적복합재료，과립월소，응변제도월고，강화효과월호。저일결 과게시료，과립강화급척촌효응주요시통과응변제도효응래표현적。저야동시설명，응변제 도가능시공제재료변형여단렬적중요인소지일。
Although much efforts have b een made to understand the relationship between microstructures and deformation behaviors of particle-reinforced metal matrix composites(PRMMCs) during the pas t several decades,there are still some phenomena remained to be understood,one of which is size effects in PRMMCs.Recently,many experimental results demonstrate t hat reinforcing particle sizes have a significant influence on yield and flow st resses of PRMMCs.However,various micromechanical models which are based unpon ho mogenization technique for particulate composites predict particle volume fracti on effects on deformation behavior of composite materials but show an independen ce of particle sizes.According to this observation,a strengthening-strain gradi en t relation for particle-reinforced metal matrix composites was developed by mak ing use of the concept of geometrically necessary dislocation and proposed dislo cation model.A comparison with existing experimental results demonstrates that t he relation predicts a dependence of yield and flow stresses of composites on re i nforcing particle sizes.From this relation,we found that the strengthening effec t of mechanical behavior of composites is controlled by both characteristic micros tructure geometrical parameters and strain gradient in matrix.For a given PRMMCs ,the strengthening effect of the composite is completely controlled by particle si ze or strain gradient in the matrix.This tells us that the strain gradient in ma trix may be an important factor controlling deformation and fracture behavior of heterogeneous material systems.Moreover,effects of characteristic microstructur e geometrical parameters on deformation localization of PRMMCs are also discussed.