Computer Science
Scientific paper
Jul 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992metic..27q.249l&link_type=abstract
Meteoritics, vol. 27, no. 3, volume 27, page 249
Computer Science
1
Scientific paper
Yanzhuang (H(sub)6) is a recent meteorite fall (October 31, 1990) from P.R.China [1]. It is one of the most severely reheated, most heavily shocked chondrites. This partly shock-melted meteorite was subjected to shock heating 2.6 Ma ago at the time it was spalled off its parent body and came into being as a meteoroid of ca. 30 cm radius (Begemann et al. 1992, personal communication). The melt phase contains round and elliptic FeNi-FeS blobs of various sizes ranging from 5 micrometers to 7 micrometers. The metal in the blobs shows the distinct dendritic structure in the forms of round, needle-like, spear-like, and petal-like dendrites which form the dendritic, beads-shaped and network structure characteristic of fast cooling [2]. Since the local melting, cooling and recrystallization of FeNi metal occur in the environment of microgravity, high vacuum and superlow temperature of space, the Yanzhuang chondrite serves as a valuable specimen for microgravity research on the mechanism of crystallization of FeNi metal in space. Results: Systematic SEM, CLSM, and EDX studies have revealed the following results: (1) The specific tetra-concentric-ring growth pattern (or growth line) is well developed on the head of each of the FeNi metal dendrites. The development and growth of this tetra-concentric-ring growth line is identical in the three-dimensional directions. (2) EDX analyses of the surface of the metal in blobs give an average chemical composition (wt%): Fe 85.40+-2.37, Ni 11.41+-2.26, equivalent to plessite composition. (3) SEM study shows the specific distribution of Ni in dendrites (Fig. 1). Each of the FeNi metal dendrites consists of a core (50-100 micrometers in size) and a thin crust (about 1 micrometer in thickness). The average chemical composition of the core is Fe 90.67+-0.96%, Ni 9.34+-0.95%, equivalent to martensite composition, but its X-ray diffraction pattern shows that it has the alpha-FeNi (kamacite) structure. The chemical composition of the crust is Fe 81.0+-3.35%, Ni 18.91+-3.95%, equivalent to gamma-FeNi(taenite). Conclusions: (1) The presence of gamma-FeNi crust and the alpha-FeNi core for each of the FeNi metal dendrites reflects fast cooling of the partly shock-melted Yanzhuang chondrite in space. (2) The Kamacite-Taenite-Plessite microstructure revealed in Yanzhuang has some similarity to the idealized nickel-iron meteorite microstructure for iron meteorites proposed by P.Z.Budka [3], so our study has provided evidence for formation of some iron meteorites through shock melting of ordinary chondrites. (3) Tetra-concentric-ring growth pattern is considered as the fundamental form of crystallization of FeNi metal in space, and the FeNi metal dendrites are thought to be formed as the results of the transfer and interaction of the separated tetra-concentric-ring growth structure under the microgravity conditions. References: [1] XIE Xiande et al. (1991) Abstracts 54th. Annual Meeting Meteorit. Soc. p. 254. [2] LI Zhaohui, XIE Xiande, and ZHANG Datong (1991) Abstracts 54th Annual Meetmg Meteorit. Soc. p. 134-135. [3] Budka, P.Z.(1988) Metallurgical Transaction A, Vol. 19A, p. 1919-1923. Figure 1, which in the hard copy appears here, shows an etched section of FeNi metal dendrites showing the core-crust microstructure.
Li Zaidong
Xie x.
Zhang Dengfu
No associations
LandOfFree
On the Mechanism of FeNi Metal Crystallization from Shock Melt in Space does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with On the Mechanism of FeNi Metal Crystallization from Shock Melt in Space, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and On the Mechanism of FeNi Metal Crystallization from Shock Melt in Space will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1209530