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利用A356合金研究拉力在热裂的形成及其断裂行为中的作用。利用一个新型的实验装置进行相关实验研究。该实验装置能够同时测量并采集受限试样在凝固过程中施加的拉力和温度的数据。这些数据可以用来研究热裂的萌生和扩展。研究了在不同加载速度下,固相率的演变和热裂的形成之间的定量关系。由实验结果可知,施加的拉力在热裂萌生初期起着复杂的作用。在合金凝固过程中,随着固相率的不断增加,拉力会逐渐增大直至最大值,然后急剧下降,此时试样出现裂纹并在拉力的持续作用下产生断裂。对于A356合金,产生早高温下产生断裂的临界应力是0.1 MPa。由热裂纹的断口形貌可知,在凝固末期形成的晶间搭桥和液膜褶皱对热裂的形成起重要的作用。
A356 alloy was used to study the role of tensile force in the formation of hot cracking and fracture behavior. Use a new type of experimental device for experimental research. The experimental device can simultaneously measure and collect the data of the tensile force and temperature exerted by the constrained sample during the solidification process. These data can be used to study the initiation and propagation of thermal cracks. The quantitative relationship between the evolution of solid fraction and the formation of thermal cracking at different loading rates was investigated. It can be seen from the experimental results that the applied tension plays a complex role in the early stage of thermal cracking. During solidification of the alloy, as the solid fraction increases, the tensile force gradually increases up to the maximum value and then drops sharply. At this point, the specimen cracks and breaks under the continuous action of tension. For the A356 alloy, the critical stress producing fracture at high temperature is 0.1 MPa. It can be seen from the fracture morphology of hot cracks that the intergranular bridge and liquid film folds formed at the end of solidification play an important role in the formation of thermal cracking.