Troubleshooting Cracks in NiTiHf Alloy Produced Through VIM Process

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SUMMARY

The discussion centers on the occurrence of cracks in a NiTiHf alloy ingot produced via the Vacuum Induction Melting (VIM) process. The cracks appear after homogenization at 1000 °C and subsequent water quenching. The primary cause identified is the design of the casting mold, which may lead to non-proportional heat loss during solidification. Recommendations include avoiding right angle transitions in mold design and opting for polynomial transitions to minimize uneven cooling stresses.

PREREQUISITES
  • Understanding of Vacuum Induction Melting (VIM) process
  • Knowledge of alloy solidification principles
  • Familiarity with mold design characteristics
  • Experience with thermal stress management in casting processes
NEXT STEPS
  • Research mold design techniques for casting NiTiHf alloys
  • Study the effects of cooling rates on alloy solidification
  • Learn about polynomial transitions in mold design
  • Investigate methods to reduce thermal stresses during solidification
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Materials scientists, metallurgists, and engineers involved in alloy production and casting processes, particularly those working with NiTiHf alloys.

mah65
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Hi guys

I have produced an ingot of NiTiHf alloy through Vacuum Induction Melting (VIM) process and by using pure materials of Ni, Ti and Hf. Casting was done in a Y2O3-coated steel mold, and the crucible was made of graphite.

The problem is that, when I homogenize the ingot at 1000 oC and then quench it in water, some cracks happen in it. I have done this process several times before, but no crack was visible. These cracks are deep inside the ingot, which may hinder the rolling process.

What may be the reason for such cracks in this alloy ?

thanx
 
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one possible reason for this problem may be the design of the mold, in which the melt is cast. That is, these cracks may happen during the casting & solidification due to inappropriate and non-proportional heat loss, and not during the homogenization. Thus, the design of my new mold for casting may be the cause of the cracks.
What considerations should I give when I want to design a new mold? I mean what should I do to reduce the stresses that give rise to cracks during solidification? What are the characteristics of an appropriate mold?
 
mah65 said:
one possible reason for this problem may be the design of the mold, in which the melt is cast. That is, these cracks may happen during the casting & solidification due to inappropriate and non-proportional heat loss, and not during the homogenization. Thus, the design of my new mold for casting may be the cause of the cracks.
What considerations should I give when I want to design a new mold? I mean what should I do to reduce the stresses that give rise to cracks during solidification? What are the characteristics of an appropriate mold?

try to avoid right angle transitions, its most preferred to use polynomial transitions in order to avoid uneven cooling tension.
 

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