Microhardness and brittle fracture of garnet single crystals
Microhardness and brittle fracture of garnet single crystals
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石榴石单晶的显微硬度及脆性断裂
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发表时间：
1984
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通讯作者：
M. Pardavi
中科院分区：
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作者：
M. Pardavi
使用维氏显微硬度测试在 25 至 100 g 的低载荷范围内测量硬度和断裂韧性，接近接近完美的石榴石单晶的断裂阈值。研究了晶体生长参数、钙杂质含量和晶体取向对 Gd3Ga5O12 (GGG) 和 Ca3Ga2Ge3O12 (CaGeGG) 样品的影响。断裂始于凹角处的径向裂纹，然后是两种不同模式的横向断裂。 [111]取向GGG的平均硬度为H=13 GN m−2，[111]取向CaGeGG的平均硬度为12 GN m−2，两种晶体的平均断裂韧性分别为Kc=1.2和0.8 MN m−3/2。杂质掺杂会稍微增加材料的强度。在所研究的晶体中，(111) 面的强度最低，(100) 面的 CaGeGG 的 H 和 Kc 值最大。约束因子 φ 和屈服应力 Y 由测量的硬度数据推导出来，给出 φ=2.2，Y 约为 7 GN m−2。
Hardness and fracture toughness were measured using the Vickers microhardness test in the low load range from 25 to 100 g near to the fracture threshold for near-perfect single crystals of garnets. The influence of crystal growth parameters, calcium impurity content and crystallographic orientation of Gd3Ga5O12 (GGG) and Ca3Ga2Ge3O12 (CaGeGG) samples was investigated. Fracture starts with radial cracking from indent corners followed by lateral fracture of two distinct modes. The mean hardness of [111] oriented GGG isH=13 GN m−2, for [111] oriented CaGeGG it is 12 GN m−2, the average fracture toughness beingKc=1.2 and 0.8 MN m−3/2, respectively for the two crystals. Impurity doping slightly increases the strength of the material. Among the investigated crystals (111) faces are the least strong, the (100) face has maximumH andKc values for CaGeGG. The constraint factor,φ, and yield stress,Y, were deduced from the measured hardness data, givingφ=2.2 andY about 7 GN m−2.