为了准确表征铸造铝合金气缸盖材料微观组织与失效概率之间的相关性，提出综合反映材料强度和试样尺寸对失效概率影响的评价方法。首先，基于气缸盖不同位置微观组织表征和力学性能测试结果，利用灰色关联分析方法，以二维孔隙率、孔隙面积、孔隙最大Feret尺寸、硅相面积、硅相长宽比、硅相最大Feret尺寸和硅相颗粒圆度7个微观组织特征作为比较序列，以抗拉强度、弹性模量和维氏硬度3个力学性能指标作为参考序列，研究气缸盖材料组织特征与力学性能之间的关联关系。基于最弱链理论，通过考虑缺陷分布偏离理想均匀分布程度，构建了弱化试样尺寸效应的广义双参数Weibull分布模型，对气缸盖不同位置失效概率与材料强度关系进行描述。结果表明：孔隙最大Feret尺寸对铸铝气缸盖本体材料力学性能的影响相对较大，底板位置容易出现局部缺陷的集中分布，发生由铸造缺陷引起失效的概率较高。

An evaluation method collectively reflecting the influence of material tensile strength and specimen size on the failure probability was introduced to accurately characterize the correlation between microstructure and failure probability of cylinder head material. Firstly, based on the results of microstructural characterization and mechanical property testing of different positions in cylinder head, the grey relational analysis method was employed to reveal the relationship between microstructural characteristics and mechanical properties by using two-dimensional porosity, pore area, pore maximum Feret size, silicon phase area, silicon phase length-width ratio, silicon phase maximum Feret size, silicon phase particle roundness as relevant sequences and using tensile strength, elastic modulus, Vickers hardness as reference sequences. Based on the weakest chain theory, a generalized two-parameter Weibull distribution model with weakened specimen size effect was built to describe the relationship between failure probability and material strength at different locations of cylinder head by considering the degree of defect distribution deviation from the ideal uniform distribution. The results showed that the pore maximum Feret size had a relatively large role in influencing the mechanical properties of cast aluminum cylinder head body material, the bottom plate position was prone to the centralized distribution of local defects, and the probability of failure caused by casting defects was higher.