Al-TiO_2-C系原位合成铝基复合材料高温拉伸性能及断裂机理

Mechanical Properties of the Composites Fabricated by In Situ Method in AlTiO_2-C System

讨论了Al-TiO2-C反应系原位反应合成铝基复合材料的常温和高温拉伸性能及其断裂机理。当C/TiO2摩尔比为0时,增强相由α-Al2O3和Al3Ti组成,随C/TiO2摩尔比的增加,Al3Ti逐渐减少,在C/TiO2摩尔比为1时,Al3Ti基本消失。室温抗拉强度和延伸率随C/TiO2摩尔比的增加而同步提高,分别由250.4 MPa和4.0%上升到350.8 MPa和6.0%。SEM观察发现有的Al3Ti自身解理开裂,并在四周形成较大韧窝,拉伸时裂纹核可在Al3Ti棒中和基体中α-Al2O3的聚集处形成,并分别在棒的解理面和基体中扩展引起断裂。高温时,热错配应力促使裂纹核先于基体在Al3Ti棒与基体的界面萌生扩展,Al3Ti从基体中脱离,断口出现洞坑,C/TiO2摩尔比为1的复合材料在727K时,拉伸强度降为93.3MPa,延伸率升为11.0%。

The room and elevated temperature mechanical properties, and fracture mechanism of the composites fabricated by in situ reaction method in the Al-TiO2-C system were studied. The results indicate that when the C/TiO2 mole ratio is zero, the reinforcements of the composites are composed of α-Al2O3 and Al3Ti, the ultimate tensile strength and elongation at room temperature are 250.4MPa and 4.0% respectively. The fracture mechanism of the composite is characterized by crack nuclei initiating and propagating in the some Al3Ti rods and segregation region of the α-Al2O3 in the matrix. When the C/TiO2 mote ratios increases, the amount of Al3Ti phase decreases. When the C/TiO2 mole ratio reaches 1, the Al3Ti phase almost eliminates, the ultimate tensile strength and elongation are promoted to 350.8MPa and 6.0% respectively. There are big ductile dimples around the Al3Ti and some fractured Al3Ti in the tensile cross section surfaces of the composites. With increasing the test temperature, the ultimate tensile strengths decrease and the elongations increase. The bonding strength of the Al3Ti with matrix decreases and the Al3Ti rods are pulled out from the matrix. The crack nuclei initiate and propagate in the interfaces of the Al3Ti rods with matrix are previous to taking place in the matrix. At the test temperature of 727K, the tensile strength and elongation of the composites with C/TiO2 mole ratio of 1.0 are 93.3MPa and 11.0% respectively.