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Accumulative Roll Bonding TZM Alloy Microstructure

TZM alloy after severe plastic deformation (SPD) the grain size is less than 1um, and it can improve the strength and toughness of the alloy to a certain extent. Accumulative toll bonding is one of SPD methods. People usually use in aluminium alloy plate and low carbon steel for refined crystalline strengthening. So many manufacturers use it for TZM alloy’s property improvement.

Observing TZM alloy’s microstructure by low magnification SEM photograph found processed ordinary rolling TZM alloy has fine grain size and has clear direction. Besides, there are a lot of elongated grains. After the first accumulative roll bonding, there are some local small crake, and these crake will lead to fracture. For another thing, the grains are coarser. On the basis of the first accumulative roll bonding to do the second rolling found alloy grain refinement is significantly, and the cross-sectional structure uniformity is improved. After third and fourth accumulative roll bonding was observed electron microscope photograph found, with rolling quantity increase, the composite surface position is more difficult to identify. This is mainly because, after many accumulated roll bonding deformation, bonding interface corresponding occurs strain gradually to achieve a good combination between the substrate, namely, the grain growing up, stretching, making the toughness of the alloy increased. And many stretched and elongated grain occur recovery and recrystallization, indicating high temperature rolling and annealing has negative impact on rolled refinement grain.

In the accumulative roll bonding process, TZM alloy’s fine grains directly into the center of the alloy by a composite process, and the internal grain will be refined. On the other hand, with rolling degree increases, the degree of grain refinement, dislocation density and interface quantity has a corresponding increase.

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