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Dialog of "particle engulfment and tensing by strengthening interfaces: Section IIMicrogravity researches and theoretical diagnostic / author's answer
The article of Stefanescu et al. [1]deals with experimental willpower of the pushing/engulfment conversion (Furry friend) within the Al/ZrO^sub 2^ system under microgravity conditions and also with the theoretical diagnostic of this conversion, such as, with the theoretical computation of the critical interface velocity for Furry friend.
The researches functioned under microgravity conditions in the course of the LMS Assignment on board the space taxi Columbia are the initial of this type, and the effects offer a good chance to speak about theoretical back ground of the pushing/engulfment phenomenon without the results of sedimentation of particles and convection of the liquefy.. Within the ground experiments,[2] the experimental critical velocity for
The chief aim of this dialog is to speak about Part IV, "THEORETICAL Diagnostic" and the connected APPENDIX of the article.[1] The key reason for this dialog 's the misleading way my personal article[5]has been referenced (under Useful resource 29 in Useful resource 1). But still, the dialog is more general; therefore,, let me run after the article[1] in its order of debate in its Part IV and summarise my comments in a numbered path to make the authors' answer simpler to create and know. In later debates, original equations of the article[1] are numbered as Eq. [x], whilst equations use within this text are numbered as Eq. (x). Icons are utilized as given within the LIST OF Icons of Useful resource 1.
Discourse 2. On the critical distance of the particle from inside the interface (is needless to say the dearth of informations on Ato value 's the major and merely shortcoming in developing Furry friend hypotheses?)
Discourse 3. On the variation amidst the sigma and gamma amounts.
It was most likely not the goal of the authors[1] to characterize two distinct physiological amounts, delta^sub PL^ and gamma^sub PL^, as surface stress and surface energy of the particle-liquid interface, for instance. If it was, I request for explanation of the variation. If not, let me make clean which delta^sub PL^ = gamma^sub PL^, and delta^sub Playstation^ = gamma^sub Playstation^. To the discrepancy amidst the delta(sigma)^sub 0^ and delta(gamma)^sub 0^ amounts as outlined by Eqs. [4] and [7], I'll talk about this in time. In order to evade jumble, later in my dialog, a would be used no matter if gamma was made use of by the writers. [1]
Discourse 5. On the meaning of the worthiness sigma^sub Playstation^ (or gamma^sub Playstation^).
Discourse 6.
....[1] But still, for other ceramic/metal couples, the 2 proceedings normally could result in distinct digits.
(2) The low, positive value of delta(sigma)^sub 0^ computed here certifies the low critical velocity for Furry friend found experimentally in Useful resource 1.
The question of particle tensing and engulfment is really so complicated from inside the theoretical view point. Even within the most elementary case of microgravity conditions, when both liquefy convection and particle sedimentation or floating as a result of thickness discrepancy are eliminated, as follows burdens must be separately resolved in an appropriate way, and therefore the resulting equations must be intermix in to the fair final algorithm: (1) the willpower of the critical distance,
(4) willpower of the relevant physiological constants effective in the course of the Furry friend exhibition.
This era, all four of the preceding burdens have quite a few contradicting "resolutions." I wrote this dialog article to sketch the alert cognitive state of the readers of this Journal about the existence of this debatable and challenging circumstance.
ACKNOWLEDGMENTS
I am thankful to Dr.. Stefanescu for inviting me to his laboratory in 1991 and for introducing me about the wonders of the particle tensing trouble. I am also thankful to almost every other writers of the articlet[1] for their handy debates above days gone by years.
REFERENCES
1.. Stefanescu, Emergency room. Juretzko,. Dhindaw, A. Catalina, S. Sen, and dad. Curreri: MetalL Mater. Trans. A, 1998, vol. 29A, pp. 1697-1706.
2. Emergency room. Juretzko,. Dhindaw,. Stefanescu, S. Sen,. Curreri: Metall. Mater. Trans. A, 1998, vol. 29A, pp. 1691-96.
3.. Shangguan, S. Ahuja,. Stefanescu: Metall. Trans. A, 1992, vol. 23A, pp. 669-80.
4. Q.. Hunt: Iron Steel Inst. Jpn. Int., 1995, vol. 35 (6), pp. 693-99.
5. G. Kaptay: Mater. Sci Discussion board, 1996, vols. 215-216, pp. 467-74.
6. S. Sen,. Dhindaw,. Stefanescu, A. Catalina, and dad. Curreri: J. Cryst. Maturation, 1997, vol. 173, pp. 574-84.
7.. Uhlmann, B. Chalmers,. Jackson: J. Appl. Phys., 1964, high pr domains vol. 35, pp. 2986-93.
8.. Neumann,. J. Szekely,. Rabenda: J. Colloid Interface Sci., 1973, vol. 43, pp. 727-32.
9. G. Kaptay: Submitted to Metall. Mater. Trans. in April, 1999.
10. G. Kaptay: Mater. Sci. Discussion board, 1996, vols. 215-216, pp. 475-84.
11. G. Kaptay: Proc. EUROMAT 97 Conf., vol. I, Alloys and Composites,.. Zeedijk, eds., FEMS, Maastricht, 1997, pp. 435-38.
A dozen. G. Kaptay: Proc. HTC 97, N. Eustathopoulos and N. Sobczak, eds., Foundry Research Institute, Cracow, Poland, 1998, pp. 388-93.
13.. Li: Ceram. Int., 1994, vol. 20, pp. 391-412.
14. G. Kaptay: Mater. Sci. Discussion board, 1991, vol. 77, pp. 315-30.
15. N. Eustathopoulos, L. Coudurier,. Joud, and P. Desr&: J. Cryst. Maturation, vol. 33, 1976, pp. 105-45.
16. D. Camel, N. Eustathopoulos, and P Desre: Acta Metall., 1980, vol. 28, pp. 239-47.
17. M. G*nduz and J. D. Hunt: Acta Metall., 1985, vol. 33, pp. 1651-72.
18. M. Gndz and J. D. Hunt: Acta Metall., 1989, vol. 37, pp. 1839-45.
Authors' Respond
. STEFANESCU,. JURETZKO, A. CATALINA,. DHINDAW, S. SEN, and dad. CURRERI
The dialog contributed by Dr. Kaptay[1] to our article[2] is sort of greet in which it makes clear the problem and the challenges of the analysis of the tensing engulfment conversion (Dog) of inert particles by strengthening interfaces. Because, according to Dr. Kaptay, "the key reason for this dialog 's the misleading way my personal article has been referenced," this matter probably will be addressed first. Within the Appendix to our article, the number delta(sigma)^sub 0^ proposed by Uhlmann et al.[3] was derived as Eq. [Al]. This derivation followed which proposed by Kaptay in a personal communication to us next his last holiday in the Solidification Lab, College of Alabama. Whilst the derivation proposed in his article [4] is mildly dissimilar, the outcome is similar:
On the negative aspect of typos, we wish to adjust some auxiliary ones. Equations [17] through [20] within the body of the Appendix have to read [A2] through [AS].
In his discourse 4, Dr. Kaptay further gripes which other results from his article "are overlooking from a article,"[2] and he proceeds in itemizing them in his dialog. Again, we haven't used his theoretical work, with that, since it could become clean from a tracking dialog, we don't agree; thus, we didn't feel obligated to present the listings. His article on the topic is publicized and completely ready to whomever is amused. Accordingly, we think that this citation is reasonable, and not in the least misleading.
In responding the remaining of the dialog on our article, quite than tracking the comments sequentially, we elect to address the pertinent issues within the tracking order:
(1) the equation for the critical velocity of Dog (discourse 2);
(2) the drag coerce (discourse 1);
(3) the appraisal of interface powers (comments 3 through 5); and
(4) the metal-ceramic researches (introductory comments).
Eventually, in our latest model[2] (SJD98), we certainly have also excluded the desire to assume a worth for d^sub cr^. The wonderful thing about this model is which it may at present foretell, with fair accuracy, the critical velocity for diverse matrix-particle systems with no changeable parameters. A listing of approval results for the SJD98 model for diverse systems is supplied in Table I. Realize that, as predicted, ground researches ordinarily show a taller critical velocity due to the contribution of convection.
But still, once the solidification velocity is taller than the critical velocity (V^sub s^ = 2 (mu)m/s), as the particle tactics the interface, the drag coerce is appreciably taller than the interface coerce. The particle is consistently decelerated and the system can't reach continuous state. Another coerce probably will be thought out. If this coerce isn't incorporated, so therefore harmony would be set forth far away smaller than d^sub cr^ It's because F^sub D^ speeds up with lid, whilst F^sub gamma^ speeds up with 1/d^sup 2^. Thus, there has always a distance at that F^sub gamma^ > F^sub D^. This supplies the look which the model always forecasts tensing. A proper translation is which the SJD98 model could describe the physics just up about the critical velocity. Over V^sub cr^ continuous state breaks down and engulfment is assumed.
This diagnostic illustrates the restriction of steady-state editions, which by quality inside their rudimentary supposition, they disregard the contribution of particle swiftness about the coerce balance. We now improved a lively model to be submitted for e-newsletter. As well as that, a statistical model is under development.
Astonishingly, Dr. Kaptay alleges (discourse 1) which, because the vintage Stokes coerce is approximately 6 times taller than which computed with Eq. [2], it ought to be used in lieu. Supposedly, his affirmation is which the biggest calculable drag coerce can be used. But still, the derivation of Stokes coerce lies in unperturbed circulation and can't describe the present phenomenon that causes restrictive circulation amongst the particle and the interface. The problem is not that coerce is larger, but quite the purpose of the suitable equation which appropriately clarifies the physics. Accordingly, our choice of drag coerce is right.
Dr. Kaptay[4] has proposed a dissimilar definition for delta(sigma)^sub 0^ (discourse 4) than which use within our article. The writers were aware about this development at that moment the article was documented, from Kaptay's personal communication and, later on, from his publicized article. His hypothesis hasn't been approved by us and therefore wasn't use within our examines. The justifications for this discord are relevant to a few of the presumptions use within the numerical derivation. This can be presented in depth within the tracking paragraphs.
Let us talk about the derivation of the interface coerce proposed by Kaptay.[4] We're going to begin the study with his Eq. [8] reproduced in time:
This is further corroborated from informations which Kaptay's formulated in a dissimilar article[12] where he has computed (in his Table 5) interface powers for the Al-SiC system, speculative both oxidized and not oxidized aluminum surfaces. These valuations are reproduced in Table II.
It's really seen which for the situation of oxidized aluminum, sigma^sub Playstation^ > sigma^sub PL^. This contradicts the elemental supposition of his model presented in Statistic 2(a). But still, for the not oxidized aluminum, the realization holds. Surely, the perfect case scenario would be which sigma^sub Playstation^ == sigma^sub PL^, as highly recommended in Kaptay's discourse 5, Eq. [10].
In his discourse 6, Dr.. The initial value complies with to a heat level of 1100 deg C, whilst the aluminum complies with to 700 deg C (Useful resource 13). His opposition is which below 1,000 deg C, aluminum is covered by a slim alumina oxide stratum. This stratum progressively cuts down in density as the heat level speeds up. Thus, the upper value doesn't really represent the case within the Al-ZrO^sub 2^ liquefy,.
The evaporation-reduction response of the alumina motion picture by liquid aluminum at taller temperature ranges is well written within the literature. For instance, for the Al-SiO^sub 2^ system at 1073 K,. But still,,, within the authors' idea,. The lessen of the density of the alumina stratum has a smaller contribution. Not surprisingly, as represented in Statistic 8 of our article,[2] at temperature ranges of 950 deg C, zirconia particles react with the aluminum liquefy. As follows response comes up:
In his introductory comments, Dr. Kaptay alleges, referring about the Recommended Reading experimental critical velocity insistent in our ground experiments,[18] which "it's possible which the pup within this system is hooked up with subsidiary causes namely convection of the liquefy quite with interfacial forces taken into mind within the model." Whilst we most definitely accept to this discourse, we're truthfully bewildered by it since we reckoned which we made this clean in our article. Not surprisingly, we made clear in depth the role of convection through Statistic 1 in our article[2] and indeed within the text. We wrote, "from Eq. [1a], it's really seen which the lift coerce (formulated by convection) 're going to work like another grotesque coerce and, so,, will vary the critical velocity." To split the role of convection was the chief drive of this exploration.
We think that we certainly have demonstrated Dr. Kaptay's criticism to be mainly unsupported. Nonetheless, we think that some further dialog of the chief issues confronting research workers fascinated by the sector of particle tensing is advantageous. Whilst massive amounts of labor has been functioned on particle tensing, we think that the sector 's still in its babyhood. The chief regions of activity which we perceive are the following:
(1) experimental work to judge the critical velocity for alloys and metals doped with ceramic particles, both on ground and in microgravity;
(2) experimental work to narrow down the costs of interface powers for metal-ceramic systems of interest; and
(3) development of statistical editions that are able to contain the complexnesses of non-steady-state phenomena linked with Dog.
Our present efforts fit beneath the first and 3rd devices. Definitely acquiring informations on other systems than Al-ZrO^sub 2^ is worth chasing. The chief restriction is transparency to Xrays, that is immediately the tactic of substitute for measure particle whereabouts. The statistical model will likely need to think about the alter of liquefy viscosity within the border stratum. That's, as the particle-interface distance cuts down beneath the micrometer grade, the viscosity speeds up. As well as that, the guesstimate immediately employed for K*, that's based on the relationship amongst K* and the radii of the particle and the interface at d = 0, should also be developed upon. In most cases, there has still a necessity for work, both theoretical and experimental.
[Useful resource]
REFERENCES
[Useful resource]
1. G. Kaptay: Metall. Mater. Trans. A, 1999, vol. 30A, pp. 1887-90.
2.. Stefanescu, Emergency room. Juretzko,. Dhindaw, A. Catalina, S. Sen,. Curreri: Metall. Mater Trans. A, 1998, vol. 29A, pp. 1697-1705.
3.. Uhlmann, B. Chalmers,. Jackson: J. AppL Phys., 1964, vol. 35, pp. 2986-93.
4. G. Kaptay: Mater Sci. Discussion board, 1996, vols. 215-216, pp. 467-474.
5.. Shangguan, S. Ahuja,. Stefanescu: Brass Trans. A, 1992, vol. 23A, pp. 669-80.
6. S. Sen,. Dhindaw,. Stefanescu, A. Catalina, and dad. Curreri: J. Cryst. Maturation, 1997, vol. 173, pp. 574-84
[Useful resource]
7. A. Cottrell: Unveiling about the New age Hypothesis of Af Alloys, The Institute of Alloys, London, 1988.
8... Catalina: Iron Steel Inst. Jpn., Int., 1998, vol. 38 (5) pp. 503-05.
9.. Stefanescu, Emergency room. Juretzko,. Dhindaw, S. Sen, and dad. Curreri: NASA Microgravity Materials Science Conf, 1998, pp. 599-604.
10... Cisse: J. Cryst. Maturation. 1971, vol. 10, pp. 56-66.
11... Rohatgi: Metall. Mater. Trans. A, 1998, vol. 29A, pp. 351-58.
[Useful resource]
A dozen. G. Kaptay: Mater. Sci. Discussion board, 1996, vols. 215-216, pp. 475-84.
13.. Li: Ceramics Int., 1994, vol. 20, pp. 391-412.
14. V. Laurent, D. Chatain, and N. Eustathopoulos: Mater. Sci. Eng., 1991, vol. A135, pp. 89-94.
15. N. Eustathopoulos, D. Chatain, and L. Coudurier: Mater. Sci. Eng., 1991, vol. A135, pp. 83-88.
. Y. Naidich: Kontaktnie Javelenia v Metallicheskih Rasplavah, Naukova Dumka, Kiev, 1972.
17. N. Eustathopoulos and B. Drevet: Mater. Sci. Eng., 1998, vol. A249, pp. 176-83.
18. FR. Juretzko,. Dhindaw,. Stefanescu, S. Sen,. Curreri: Metall. Mater. Trans. A, 1998, vol. 29A, pp. 1691-96.
[Author Network]
. STEFANESCU, FR. JURETZKO,. DHINDAW, A CATALINA, S. SEN, and dad. CURRERI: Metall. Mater Trans. A, 1998, vol. 29A, pp. 1697-1706.
G. KAPTAY, Associate Teacher and Skull, Division of Bodily Chemistry, and Dean, Faculty of Metallurgical Engineering, is with the College of Miskolc, Miskolc, Egyetemvaros, 3515 Hungary.
Dialog submitted Aug 10, 1998.
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