SiC颗粒增强铝合金基梯度复合材料拉伸力学性能及其评价

对SiC颗粒增强铝合金基梯度复合材料的拉伸力学性能进行了研究。提出了一种新的材料力学性能评价指标——梯度系数K_x。理论研究表明,金属基梯度复合材料(MMGC)各组分性能的差异使其在拉伸变形时产生了三轴应力。实验及断口分析表明,由拉伸试验获得的材料平均力学性能指标弹性模量E和屈服强度σ_0.2近似符合ROM法则;此类材料的拉伸力学性能受SiC颗粒梯度分布方式的影响。外层为基体,芯部为高SiC含量的材料拉伸断口具有韧性断裂特征,能发挥其性能优势。反之,断口表现出脆性断裂特征,降低了材料的力学性能;受多种因素影响,裂纹穿过层间界面时,会引起断裂方式和扩展方向的改变。当梯度层间SiC颗粒体积分数相差较大时,材料会产生分层开裂;梯度系数K_σb和K_δ可反映材料的梯度分布方式和性能的优劣程度,梯度系数K_E则反映了材料性能的稳定性程度。

TENSILE MECHANICAL PROPERTIES AND ITS EVALUATION OF ALUMINIUM ALLOY MATRIX GRADIENT COMPOSITESREINFORCED WITH SiC PARTICLES

The tensile mechanical properties are studied for the aluminium alloy matrix gradient composites reinforced with SiC particles. Gradient coefficient Kx, a new evaluating index of mechanical properties of materials, is put forward. The results of the basic research show that a tri-axial stress will be produced in the tensile specimens because of components property difference of the metal matrix gradient composites (MMGC). The results of the tensile test and fracture analysis show that the elastic modulus E and yield strengthσ0.2 of the MMGC obey approximately the Role of Mixture (ROM) law. The tensile mechanical properties of the composites are remarkably influenced by the distribution of SiC particles. Fracture of the tensile specimen appears to have a toughness character and the composites can develop their potential in tensile properties when the matrix component is in outside and the component with high SiC volume fraction is in inside. Conversely, the fracture appears to have a brittleness character and mechanical properties of the composites will be decreased. The fracture way and the crack propagating orientation will be changed by the influence of many factors when the crack grows through the bonding interface. Interface cracking could be produced if there is a great difference of SiC volume fraction between two layers of the composites. The coefficients Kσb and Kδ can be used to identify gradient distribution and tensile properties level, but the coefficient KE can be used to identify steadiness extent of the composites.