VN/(Ti,Al)N纳米多层膜的共格生长与超硬效应

采用反应磁控溅射技术制备了一系列具有不同调制周期的VN/(Ti,Al) N纳米多层膜.利用高分辨透射电子显微镜、X-射线衍射仪和微力学探针表征了纳米多层膜的微结构和力学性能,从而研究其微结构与力学性能之间的关系.结果表明,小调制周期时,VN/(Ti,Al) N纳米多层膜沿薄膜生长方向呈现出具有面心立方(111)晶面择优取向的共格外延生长结构.由于存在晶格错配,在共格界面作用下,VN和(Ti,Al)N调制层分别受到拉、压应力,在多层膜中产生以调制周期为周期的交变应力场.这种应力场大大阻碍了薄膜中位错穿过界面的运动,从而导致薄膜产生硬度和弹性模量异常升高的超硬效应,并在调制周期为5.6 nm时,达到硬度和弹性模量的最高值38.4GPa和421 GPa.进一步增加调制周期,两调制层之间产生非共格界面,破坏了薄膜中的交变应力场,薄膜的硬度和弹性模量也随之降低.

The Coherent Growth and Superhardness Effect of VN/(Ti, Al)N Nano-multilayers

A series of VN/(Ti,Al)N nano-multilayers with various modulation periods were prepared(using) reactive magnetron sputtering method.The microstructure and mechanical properties of these multilayers were characterized with X-ray diffractometry,high-resolution transmission electron microscopy and nanoindentor.The relationship between the microstructure and the mechanical properties of the multilayers were studied.The results reveal that at small modulation periods VN/(Ti,Al)N nano-multilayers grow in a polycrystalline epitaxial growth mode with a(111) preferred orientation.An alternating strain field which has the same period with the modulation period was formed because of the lattice mismatch between(Ti,Al)N and VN layers during the epitaxial growth.Correspondingly,multilayers show significant hardness and modulus enhancement and the maximum hardness and elastic modulus can reach as high as 38.4 GPa and 448.8 GPa at the modulation period of 5.6 nm.Further increasing modulation period leads to the emerge of incoherent interface and the destroy of alternating stress field,accompanied by the decreased mechanical properties.