Research on twin-roll casting aluminum sandwich strip with a titanium particle-dispersed layer

This study successfully fabricated an Al-based sandwich strip reinforced with a titanium particle-dispersed central layer by twin-roll strip casting. Based on solidification theory and particle motion principles, a mathematical model was established. By investigating the particle distribution, compositional profile, hardness, and the distribution patterns of the flow field and temperature field in the melt pool, the formation mechanism of the sandwich layer in the cast strip was explored. The mathematical model results show that under the combined effects of centrifugal force, flow field, and solidification repulsion, titanium particles tend to accumulate near the core region of the melt pool, forming a particle-dispersed layer approximately 0.4 mm thick after solidification. The dispersed phase exhibits the structure in which titanium particles are encapsulated by an Al–Ti composite layer about 2.91 μm thick. The Vickers hardness in this region is approximately 42.3 HV, representing a 56.7% increase compared with the matrix material. The as-cast strip was further subjected to diffusion annealing. It was observed that with prolonged annealing time, the thickness of the TiAl 3 composite layer increased, following an exponential diffusion law. After 7 h, titanium particles were almost completely transformed into TiAl 3 . Correspondingly, the hardness increased significantly, reaching up to 56.3 HV, which is 108.5% higher than the Al matrix.