Crystallization of Ti33Cu67 metallic glass under high-current density electrical pulses

We have studied the phase and structure evolution of the Ti33Cu67 amorphous alloy subjected to electrical pulses of high current density. By varying the pulse parameters, different stages of crystallization could be observed in the samples. Partial polymorphic nanocrystallization resulting in the formation of 5- to 8-nm crystallites of the TiCu2 intermetallic in the residual amorphous matrix occurred when the maximum current density reached 9.7·108 A m-2 and the pulse duration was 140 μs, though the calculated temperature increase due to Joule heating was not enough to reach the crystallization temperature of the alloy. Samples subjected to higher current densities and higher values of the evolved Joule heat per unit mass fully crystallized and contained the Ti2Cu3 and TiCu3 phases. A common feature of the crystallized ribbons was their non-uniform microstructure with regions that experienced local melting and rapid solidification

Electropulse-induced microstructural evolution in a ferritic–pearlitic 0.14% C steel

The present work reports the experimental observation of electropulse-induced microstructural evolution in a ferritic–pearlitic steel at ambient temperature. Electropulsing initially causes the fragmentation of lamellar structure. Further treatment leads to the formation of new cementite plates aligned with the current direction. This is attributed to the reduction of the system free energy. The hardness of the material decreased with an increase in the number of electric current pulses. Electrical resistivity is thought to be responsible for the observed phenomenon

Joule-heating Effects In the Amorphous Fe40ni40b20 Alloy

The effects of Joule heating on the amorphous Fe40Ni40B20 alloy are investigated by measuring the time behavior of the electrical resistance of ribbon strips during such a treatment. The structural transformations occurring in subsequent stages of the process are studied by means of x-ray-diffraction, differential-scanning-calorimetry, and magnetic-permeability measurements. A continuous evolution from a fully amorphous to a fully crystalline structure may be followed. The crystallization mechanisms observed in Joule-heated samples differ from the ones occurring under conventional heating conditions. The electrical resistance displays a bump in the course of Joule heating. A quantitative model relating such a bump to the extra heat released to the sample by fast crystallization is proposed and discussed

Uncovering of major genetic factors generating naturally occurring variation in heading date among Asian rice cultivars

To dissect the genetic factors controlling naturally occurring variation of heading date in Asian rice cultivars, we performed QTL analyses using F2 populations derived from crosses between a japonica cultivar, Koshihikari, and each of 12 cultivars originating from various regions in Asia. These 12 diverse cultivars varied in heading date under natural field conditions in Tsukuba, Japan. Transgressive segregation was observed in 10 F2 combinations. QTL analyses using multiple crosses revealed a comprehensive series of loci involved in natural variation in flowering time. One to four QTLs were detected in each cross combination, and some QTLs were shared among combinations. The chromosomal locations of these QTLs corresponded well with those detected in other studies. The allelic effects of the QTLs varied among the cross combinations. Sequence analysis of several previously cloned genes controlling heading date, including Hd1, Hd3a, Hd6, RFT1, and Ghd7, identified several functional polymorphisms, indicating that allelic variation at these loci probably contributes to variation in heading date. Taken together, the QTL and sequencing results indicate that a large portion of the phenotypic variation in heading date in Asian rice cultivars could be generated by combinations of different alleles (possibly both loss- and gain-of-function) of the QTLs detected in this study

Elastic and Anelastic Properties of Amorphous Thin Films

The interesting non-linear elastic and anelastic properties recently found in the metal-metal and the metal-metalloid amorphous alloys will be reported. The Young's modulus Ed measured by means of the vibrating reed method with the strain amplitude εt=10-6 is found to be lower than Es in the frequency f range below (103~104) Hz, showing a minimum at around 102 Hz, and to increase beyond Es in the f range above (103~104) Hz, where Es denotes the Young's modulus in linear elasticity observed for the static tensile or bending tests. These results suggest that a certain resonant anelastic-process is excited under alternating strain in the f range below (103~104) Hz. The εt dependence of Ed measured at f=102Hz shows that Ed increases towards Es with increasing εt. Further, for the measurements at f=102Hz with t=10-6, an increase in Ed is also found but under passing an electric direct current (PEC) with 107A/m2, suggesting that internal stress is induced under PEC. These results suggest the view that a certain cluster of many atoms undergoes a resonant motion under alternating strain, and also yields internal stress due to the concentration of the electromigration force through a collective motion under PEC. The effective charge number Z* which measures internal stress induced under PEC is found to be the order of 105 for all the amorphous alloys. The number of atoms involved in the above cluster is estimated to lie between 102 and 105