Different Compression Rates Influence TZM Alloy Fracture Morphology Ⅱ

When compression rate is 60% TZM alloy has a clear dimple and the fracture mode of grains mainly transgranular fracture mode, a higher proportion of this fracture mode, indicating that the grain boundary of alloy has been some strengthening. But there is still a small part grains are cleavage fracture mode. The whole fracture mode mixed with cleavage fracture, ductile fracture and transgranular fracture mixed.

When the compression rare is 80%, the fracture morphology of TZM alloy shows the river-like pattern cleavage fracture. Although similar fracture pattern with compression rate 60% TZM alloy, but the proportion of grain which occur transgranular fracture and cleavage fracture further improved. And because the cleavage fracture during breaking process will occur plastic deformation so a lot of fibrous tissue will increase in alloy where you can see some small tearing ridge and shallow dimple belt. Usually the ductile fracture of alloy is higher when cleavage fracture happens.

When the compression rate is 90%, fracture morphology of TZM alloy is fiber microstructure and the area of fracture source can see platform, stairs and other morphology. Fracture mode is cleavage fracture and transgranular fracture. At the same time due to the plastic deformation of the grain the gaps and voids are crushed and welded together, so the gaps and voids volume of the alloy significantly smaller and reduced. The alloy has more fibrous tissue and the grains interaction coexist with each other making the alloy bonding force enhancement, material has been significantly strengthened, and tensile strength reached 846Mpa.

Effect of compression ratio of TZM alloy is mainly with the increase of the compression ratio, the alloy becomes denser and fracture mode mainly transition from ductile fracture, transgranular fracture to quasi-cleavage fracture.

Different Compression Rates Influence TZM Alloy Fracture Morphology Ⅰ

At different compression rates TZM alloy fracture morphology is different. TZM alloy which produced by powder metallurgy has four general fracture mode, along strengthen molybdenum particles internal fracture, along strengthen phase particles fracture, along the adhesion and strengthen phase internal fracture, along with enhanced adhesion particles internal fracture.
By analysis TZM alloy fracture surface under different compression ratio found that the un- rolling TZM alloy fracture mode is intergranular brittle fracture, from the SEM image can clearly see each grain exhibit polyhedral shape and full of voids. In the stretching process, these voids as source of crack and they connect with each other resulting in alloy breaks. When TZM alloy compression ratio is 40% the fracture mode is intergranular fracture and cleavage fracture, where individual grains have fracture phenomenon. At the same time, there are some small spherical particles dots and hollow on the grain boundary fracture. These spherical particles dots are TiC which play dispersion strengthen in alloys, but occurs at grain boundaries will reduce the strength of the grain boundaries to a certain extent. And because equiaxed structure and some do not weld holes exist, so the tensile strength is not high.