Cu-Zn-Al双程记忆合金中Ⅱ类孪晶的界面观察

HREM OBSERVATION Ⅱ TYPE TWIN INTERFACE IN Cu-Zn--Al TWO WAY SHAPE MEMORY ALLOY

用高分辨电镜观察了Ｃｕ－Ｚｎ－Ａｌ双程记忆合金中９Ｒ型热弹性马氏体内Ａ：Ｂ型变体对及其界面结构变体Ａ和Ｂ以［０１１］β（即［５９１］９Ｒ）为轴旋转了１８０°，呈Ⅱ类孪晶取向关系Ａ：Ｂ型变体对还具有（１１４）［１１０］９Ｒ，Ａ／／（１１４）［１９２］９Ｒ，Ｂ取向关系，在这一取向下，观察发现堆垛缺陷仅存在于变体Ａ中，变体Ａ与Ｂ以共格界面相匹配，界面为无理指数界面，即Ｋ１（１０．８４２９ ２．５８５９）．界面在原子尺度上大量存在着１—２个原子高度的结构台阶，偶尔存在７—８个原子高度的生长台阶．结构台阶面为（１１４）９Ｒ，台阶梯度方向为［２０１］９Ｒ台阶面与Ｋ１面边线夹角的测量值约为７．３°；接近理论计算值７．４５”．

HREM was employed in study the structures of 9R type martensitic variant plate pairA:B and its interface. An orientation relationship, (114)[110]9R,A // (114)[192]9R,B was found betweenthe A: B variant pair where the two variants are related by a rotation of 180°about [011]β parallel to [591]9R and form a Ⅱ type twin with an irrational interface. The illterface of A: B type is coherent and very straight. The or and β stacking faults only edest in variant A and seem not to affect the interface structure. Along the direction [192]9R,B, the atomic arrangement across the irrational A: B type interface composes of a series of stepped rational (114)9R,B planes with a step direction along [201]9R.The step is usually 1 - 2 atomic height, but occasionally 7 - 8 atomic height and forms a local bending. The measured angle is 7.3° between planes (114)9R,B and K1, which is slightly different from theoretical value of 7.45°.