The dependence of normal and abnormal grain growth in silver on annealing temperature and atmosphere

Koo, Jae Bon; Yoon, Duk Yong

doi:10.1007/s11661-001-0063-4

Cited by 70 publications

(53 citation statements)

References 39 publications

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“…It is likely that these grain boundaries were actually rough with curved shapes at the annealing temperatures and the fine scale h&v structures formed during cooling. If the grain boundaries undergo roughening-singular transitions, their structures at low temperatures will depend on the cooling rate.The correlation between the grain boundary roughening transition and the change of grain growth mode from AGG to NGG is also consistent with the previous observations in metals 13,14,[16][17][18] and oxides. 19,20) As proposed earlier, 31,32) if the singular grain boundaries migrate by the movement of existing steps or those produced by two dimensional nucleation, [21][22][23][24][25][26] v(F) will be non-linear as observed by Tsurekawa et al 30) In polycrystals with singular grain boundaries, non-linear v(F) will cause AGG as confirmed by simulation.…”

supporting

confidence: 91%

“…Normal grain growth occurred at these temperatures. This correlation between the grain boundary structure and grain growth is similar to those found in other metals [13][14][15][16][17][18] and oxides. 19,20) The results of this study thus confirm that AGG can arise from the singular grain boundary structure without any precipitates, surface energy anisotropy, or texture.…”

supporting

confidence: 86%

“…[13][14][15][16][17][18] The transition temperature of approximately 1 000°C (about 0.73 T m ) also falls into the range of 0.6-0.9 T m observed in other metals, [13][14][15][16][17][18][27][28][29] although the transition temperatures vary among the grain boundaries and depend also on additives and impurities. In 316L stainless steel, the grain boundary defaceting transitions were observed at temperatures between 1150 and 1200°C.…”

Section: Resultsmentioning

confidence: 99%

“…It was recently observed that AGG and normal grain growth (NGG) in bulk polycrystalline metals [13][14][15][16][17][18] and oxides [19][20] were related to grain boundary structures. At low temperatures or in the presence of additives, grain boundaries had hill-and-valley (h&v) shapes with singular segments and AGG occurred.…”

Section: Introductionmentioning

confidence: 99%

“…At high temperatures or with different additives, all grain boundaries were defaceted and NGG was observed. 13,14,[16][17][18][19][20] The occurrence of AGG was attributed to the step growth of singular grain boundaries. [21][22][23][24][25][26] The purpose of this work is to determine experimentally if the same correlation between the grain growth and grain boundary structure exists in pure Si (about 3 wt%) iron at different heat-treatment temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Temperature Dependence of Grain Boundary Structure and Grain Growth in Bulk Silicon-Iron.

Choi

Yoon

2003

ISIJ International

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Grain boundary shapes and grain growth in bulk 2.61 wt% silicon-iron have been studied by heat-treating at temperatures between 700 and 1 200°C. Initial microstructure with fairly uniform fine grains has been obtained by recrystallization at 800°C for 5 min after deformation. When subsequently heat-treated at 700 and 800°C, a fraction of the grain boundaries have hill-and-valley shapes with several facet planes or kinks. Some of these facet boundary segments are expected to be singular. Abnormal grain growth occurs at 700 and 800°C and is attributed to step growth of the boundaries. When heat-treated at 1 000°C, all grain boundaries are defaceted with smoothly curved shapes, indicating that they are atomically rough. At temperatures above 1 000°C, normal grain growth occurs, because the rough grain boundaries move continuously. This correlation between grain boundary structure and grain growth is consistent with the earlier observations in other metals and oxides. It is thus shown that the abnormal grain growth in this alloy occurs at low temperatures because of the singular grain boundary structure.KEY WORDS: silicon-iron; silicon-steel; abnormal grain growth; grain boundary faceting; singular grain boundary.ing along the grain boundaries using an image analysis program. For the specimens with fine grains, about 500-2 000 grains were measured, and for those with large grains, about 100-300 grains were measured. The grain boundary shapes were also examined in a transmission electron microscope (TEM). Results and DiscussionWet chemical analysis of the heat-treated bar showed that the Si content was 2.61 wt% and the major impurities were P (0.015 wt%), Ni (0.06 wt%), and Cr (0.01 wt%). The C, Mn, and S contents were about 0.005 wt%. The specimens heat-treated at 800°C for 5 min after compressing to 66.7 % in height had typical primary recrystallization structures with fine grains of 8.7 mm in average radius as shown in Fig. 1. The X-ray pole figure and electron back-scattered pattern (EBSP) analysis of these specimens did not show any macroscopic or microscopic texture. Figure 1 is the initial microstructure for all subsequent heat-treatments at various temperatures to observe the grain growth behavior.The grain growth during the heat-treatment at 600°C was very slow. After 250 h at 600°C, the grains were only slightly larger than those shown in Fig. 1. During the heattreatment at 700°C, typical AGG behavior was observed as shown in the microstructures of Fig. 2, and grain size distributions in Fig. 3. After 3 h, some large grains began to appear as shown in Fig. 2(a), and after 24 h, some grains had grown to about 700 mm radius as shown in Fig. 2(d). In Fig. 3, those large grains that could be clearly identified as the abnormal grains are marked by arrows. The fine matrix grains grew slowly as can be seen in Figs. 2 and 3.When the heat-treatment temperature was increased to 800°C, distinct AGG behavior was again observed during 24 h, but the number density of the abnormal grains was larger than that observed at ...

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