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TZM Alloy High Temperature Fracture Mechanism Affected by TiC and ZrC Doping Quantity

TiC / ZrC doping quantity have a certain influence on the microstructure and properties of TZM alloy. With the increased of TiC / ZrC doping quantity, the density of TZM alloy gradually increased, and room temperature tensile property decreased at first and then increased. Besides, when TiC / ZrC doping quantity is 0.4%, the strength of the alloy reached the highest value. Further traces of carbide can improve the high temperature strength of the alloy. The following main introduce the influence of carbide on TZM alloy high temperature fracture mechanism.

TZM alloy which does not dope with TiC / ZrC room temperature tensile fracture is typical intergranular brittle fracture. At 800 ℃ high temperature, its tensile fracture is transgranular cleavage fracture mixed with and dimple fracture. Observed the SEM photograph was found in the fracture surface of the alloy can be found the typical pattern of rivers like cleavage stage, surrounded by many small and shallow dimples.

Doped 0.4% TiC or ZrC TZM alloy at 800 ℃, there are a large number of parabolic tear dimple on tensile fracture. Besides, the dimple has bigger size and deeper, showing good plastic toughness. Because dimple is the main microscopic characteristics of metal fracture, and he main formation can be divided into three stages, microvoids nucleation, microvoids growth and microvoids aggregation. According to the second phase particle nucleation model, microvoids grew up together around the dispersed second phase particles to form dimple.

Observation doped TiC or ZrC TZM alloy high magnification SEM photograph was found, every dimple there is one or several fine second phase particles. From this, we will know doped with a small amount of carbide particles in the alloy can improve dimple to form during the high temperature stretching process, so that the high temperature fracture mechanism was changed form mixed fracture mode by the transgranular cleavage fracture and dimple to dimple fracture mode.

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