铸态镍钛形状记忆合金的断裂行为及显微组织

摘要

The as-cast ingot of equiatomic nickel-titanium shape memory alloy (NiTi SMA) was prepared by vacuum consumable are melting.The tensile tests and the compressive tests with respect to as-cast NiTi SMA were performed to study its mechanical properties of fracture.The microanalysis of as-cast NiTi SMA as well as its fractured samples was performed so as to better understand microstructure evolution and fracture behavior of NiTi SMA.Under tensile loading,the as-cast NiTi SMA shows higher plasticity and is characterized by ductile fracture at 750 ℃,but it demonstrates poorer plasticity and is characterized by cleavage fracture as well as transcrystalline fracture at room temperature and -100 °C.Under compressive loading at -100 ℃,the as-cast NiTi SMA is characterized by shear fracture where the normal to the shearing fracture surface inclines about 45° to the compressive axis,and belongs to cleavage fracture where the cracks expand via transcrystalline fracture.%通过真空自耗电极熔炼法制备等原子比镍钛形状记忆合金.为了研究其断裂力学性能,进行铸态镍钛形状记忆合金的拉伸和压缩实验.为了更好地理解镍钛形状记忆合金的组织演变及断裂行为,分析铸态镍钛形状记忆合金及其断裂样品的显微组织.在拉伸加载下,镍钛形状记忆合金在750°C时具有较高的塑性,表现为韧性断裂,但在室温和-100°C时表现出较差的塑性,具有解理断裂和穿晶断裂的特征.在-100°C的压缩加载下,铸态镍钛形状记忆合金发生剪切断裂,剪切断裂面法线与压缩轴呈45°,具有解理断裂的特征,裂纹经由穿晶断裂而扩展.