This is an interesting thread. Im not really sure why some are taking the stance that if it sounds better, dont worry about why? This is the Tech Talk forum and I believe the point for Ejliu starting this thread was to probe if anyone has a sound understanding of why cryo may make a difference, not necessarily anecdotal evidence that cryoing improves the sound of any particular piece of equipment.
As a metallurgical engineer (BS University of Illinois, 1989 for you credential seekers), I too have a guarded skepticism regarding the validity of potential mechanisms for the perceived changes/improvements attributed to cryoing mentioned in this thread. Please understand that I also rely on my ears primarily to guide me toward better sound. Since this activity is subjective in nature, I clearly dont fall into the trap, sometimes typical of engineers, that if it doesnt measure better/differently, there cant be an improvement/difference. I hear what I hear psychoacoustical explanations aside! But clearly, the point of this thread was the "WHY", right?
The asking of why is a very important step in my opinion. Technology does not advance without this step. A deeper understanding of the physical world and using this knowledge to design more advanced products is central to the technological world we live in. With all due respect to the rare black magic inventor, its the science that drives true advancement.
No one in this thread has yet offered credible science to explain why cryoing changes the sound of a component. What has been offered is speculation that whatever happens MAY be caused by a diffusionless phase change similar to a martensitic transformation. Since the temperatures involved (RT LN2) are so low, this really is the only possibility, IF the changes are caused by a reorganization of the crystal lattice. A mechanism involving mass transport (diffusion) would simply take way too long, possibly hundreds of years to accomplish.
I have a several issues with the martensitic transformation explanation though. First, transformations of this nature are not equilibrium transformations. They rely on trapping a non-equilibrium phase, usually through rapid cooling, leaving no time for the equilibrium phase to nucleate and grow. They occur very rapidly, in some cases at the speed of sound. They are basically a shear transformation, a small shift or rotation of a lattice plane, not unlike a seismic shift of plates in an earthquake. Since, in the case of ICs, PCs or SCs, there hasnt been any suggestion that cryoing must take place immediately after the Cu is solidified or drawn (strain-induced), this suggests that for a martensitic-type transformation to take place, an equilibrium phase different from RT equilibrium phase must be present on a Cu/Alloy ternary phase diagram at temperatures near LN2. Perhaps this is true, but given the extensive research in cold-temp physics, I would have assumed that the phase diagrams of commonly used materials would have been updated by now??
Secondly, if this were indeed true and the phase diagrams not understood/updated at low temperatures, then what would be the purpose for holding a component at this temperature for extended time, longer than necessary to get the temperature equalized? If it is a diffusionless transformation, time has no bearing on the volume fraction of the non-equilibrium phase present, only temperature and the rate of change of temperature are important.
Thirdly, very special conditions need to be met to practically induce martensitic transformations. By practical, I mean the cooling rates have to be reasonable. In steel, you have to alloy carefully to stabilize austenite at low enough temperatures to allow real world cooling rates to bring the piece to Ms before the onset of ferrite/pearlite nucleation. Not all materials can be forced into this type of transformation. Are we to believe that composition is unimportant for this transformation at cold temperatures, given the relatively poor heat transfer of LN2. If this were true, I would expect science would have stumbled upon this phenomenon a LONG, LONG time ago.
Finally, if this type of transformation were indeed happening, simple x-ray diffraction techniques could demonstrate this beyond a reasonable doubt. If the lattice structure changes, it is easily measurable!!!
I mean no disrespect to those that posited their thoughts on why/how perceived changes in sound may come about through cryoing. To be honest, though, without specific science to support it, it is just a guess. If anyone has access to peer-reviewed papers on the presence of meta-stable or non-equilibrium phases at low temps for the materials in question, please e-mail me or post it here. It would be wonderful for all of us if there was solid science supporting this further advancement would then be just around the corner!!
Regards,
Jordan
As a metallurgical engineer (BS University of Illinois, 1989 for you credential seekers), I too have a guarded skepticism regarding the validity of potential mechanisms for the perceived changes/improvements attributed to cryoing mentioned in this thread. Please understand that I also rely on my ears primarily to guide me toward better sound. Since this activity is subjective in nature, I clearly dont fall into the trap, sometimes typical of engineers, that if it doesnt measure better/differently, there cant be an improvement/difference. I hear what I hear psychoacoustical explanations aside! But clearly, the point of this thread was the "WHY", right?
The asking of why is a very important step in my opinion. Technology does not advance without this step. A deeper understanding of the physical world and using this knowledge to design more advanced products is central to the technological world we live in. With all due respect to the rare black magic inventor, its the science that drives true advancement.
No one in this thread has yet offered credible science to explain why cryoing changes the sound of a component. What has been offered is speculation that whatever happens MAY be caused by a diffusionless phase change similar to a martensitic transformation. Since the temperatures involved (RT LN2) are so low, this really is the only possibility, IF the changes are caused by a reorganization of the crystal lattice. A mechanism involving mass transport (diffusion) would simply take way too long, possibly hundreds of years to accomplish.
I have a several issues with the martensitic transformation explanation though. First, transformations of this nature are not equilibrium transformations. They rely on trapping a non-equilibrium phase, usually through rapid cooling, leaving no time for the equilibrium phase to nucleate and grow. They occur very rapidly, in some cases at the speed of sound. They are basically a shear transformation, a small shift or rotation of a lattice plane, not unlike a seismic shift of plates in an earthquake. Since, in the case of ICs, PCs or SCs, there hasnt been any suggestion that cryoing must take place immediately after the Cu is solidified or drawn (strain-induced), this suggests that for a martensitic-type transformation to take place, an equilibrium phase different from RT equilibrium phase must be present on a Cu/Alloy ternary phase diagram at temperatures near LN2. Perhaps this is true, but given the extensive research in cold-temp physics, I would have assumed that the phase diagrams of commonly used materials would have been updated by now??
Secondly, if this were indeed true and the phase diagrams not understood/updated at low temperatures, then what would be the purpose for holding a component at this temperature for extended time, longer than necessary to get the temperature equalized? If it is a diffusionless transformation, time has no bearing on the volume fraction of the non-equilibrium phase present, only temperature and the rate of change of temperature are important.
Thirdly, very special conditions need to be met to practically induce martensitic transformations. By practical, I mean the cooling rates have to be reasonable. In steel, you have to alloy carefully to stabilize austenite at low enough temperatures to allow real world cooling rates to bring the piece to Ms before the onset of ferrite/pearlite nucleation. Not all materials can be forced into this type of transformation. Are we to believe that composition is unimportant for this transformation at cold temperatures, given the relatively poor heat transfer of LN2. If this were true, I would expect science would have stumbled upon this phenomenon a LONG, LONG time ago.
Finally, if this type of transformation were indeed happening, simple x-ray diffraction techniques could demonstrate this beyond a reasonable doubt. If the lattice structure changes, it is easily measurable!!!
I mean no disrespect to those that posited their thoughts on why/how perceived changes in sound may come about through cryoing. To be honest, though, without specific science to support it, it is just a guess. If anyone has access to peer-reviewed papers on the presence of meta-stable or non-equilibrium phases at low temps for the materials in question, please e-mail me or post it here. It would be wonderful for all of us if there was solid science supporting this further advancement would then be just around the corner!!
Regards,
Jordan