Relationship macro and micro plasticity of titanium alloys

In assessing consructions reliability the criteria selection and evaluation of the material parameters is still discussion question. Criteria selection and material parameters must provide the integrity and constant of design construction parameters (especially  geometric) under certain operating conditions. The most important of these are: material strength, ductility, fracture toughness and fatigue, in some applications: heat resistance, tribology, and others. The plasticity of material is the parameter that is not realized in operation because the product is often operated under conditions not allowing plastic deformation.

In fact, the plasticity of the material is a guarantee that the material is not in a brittle condition, which is unacceptable and can cause uncontrolled and unpredictable construction failure. In some cases, the plasticity of the material is indirectly related to fracture toughness and fatigue.

Plasticity of the material can be divided into macro level - to change the shape of the object in plastic deformation and micro level - local deformation of the material during cracks propagation (ductility).

There is a paradigm, inherited from steel, of the inseparable connection between the two of these parameters. In some cases macro plasticity level can be estimate on micro plasticity level and vice versa.

It is shown that the macro and micro plasticity titanium alloys are connected not directly proportional. In macro-scale brittle samples level micro plastic deformation is high enough.

Relationship macro and micro plasticity significantly different in the implementation of the grain-boundary fracture.