六方结构 matrix c/a-材料的韧性和脆性 (111)twinning plane basal,pyramidal only basal slip twin and prismatic slip I basal slip and twinning (111)twinning plane matrix c/a 1.63 1.73 Fig.6.27.Influence of the c/a ratio on the deformation mode in hexagonal crystals. (a)Twinning elements of metallic crystals Lattice type Twinning plane Shear direction Displacement plane Prototype fee {111} (112) {110 Ag,Cu bec {112) (111) {110} a-Fe hcp {10i2} (10I1) (1210} Cd,Zn (b) Cd Zn Mg Co Zr Ti Be c/a 1.88 1.86 1.62 1.62 1.59 1.58 1.57六方结构 c/a --材料的韧性和脆性