铸造Al-5Cu合金准固态断裂行为的研究

Research of Quasi-solid Fracture Behavior of Casting Al-5Cu Alloys

采用SEM观察手段并结合EDX分析 ,在合金的准固态区 ,通过观察Al 5Cu Mn合金准固态拉伸和热裂应力测试试样的断口形貌 ,研究了Ti、Ce等合金元素及其交互作用对Al 5Cu Mn合金准固态断裂行为的影响及其影响机理。通过对试验合金准固态力学性能的测试和大量SEM断口的观察分析研究 ,结果表明 ,Al 5Cu Mn中添加Ti元素可明显提高合金抗热裂能力 ,主要是由于其良好的细化晶粒效果 ;适量Ce元素的加入 ,不仅可细化晶粒 ,而且其在晶间富集形成的化合物还可有效改善低熔点共晶反应在准固态区的力学行为 ,对减小热裂倾向非常有利 ;Ti和Ce的综合作用对合金抗热裂水平的提高比单一元素更有效 ;热裂的产生首先表现为枝晶枝臂的屈服 ,其后的扩展则表现为脆性断裂占优的穿晶。

The influence mechanism of elements Ti and Ce and their interactions on fracture behaviors of casting Al-5Cu-Mn alloy was studied by means of SEM and EDX instruments in quasi-solid region through observing fracture shape of quasi-solid tensile and hot cracking stress testing samples. By testing of quasi-solid mechanic properties and observing SEM fractures of the alloys, the results indicated that: resistance to hot-crack ability can be improved evidently by the addition of Ti, which contribute the grain refinement when Ce is added into the alloys, the crystal grains can be refined and dynamics behavior of low melting point eutectic reaction at quasi-solid region can be improved efficiencyly by precipitation of compound at grain boundaries, which is very favorable to diminishing tendency of hot cracking; colligate effects of Ti and Ce on the increasing of resist hot cracking ability is more efficiency than that of single alloy element; emerge of hot-crack is a yield of crystal grains firstly and thereafter its enlarge is represented to commix character of intergrainer and transgrainer of which brittleness fracture is superiority.