磁控溅射不同元素掺杂WS_(2)薄膜的组织和纳米压痕力学性能

采用磁控溅射法在不同沉积压力(0.8,1.2Pa)下分别制备WS_(2)薄膜、Ti/WS_(2)复合薄膜和La-Ti/WS_(2)复合薄膜,研究了薄膜的组织结构和纳米压痕力学性能。结果表明:WS_(2)薄膜呈疏松多孔结构,晶粒粗大,孔洞较多,组织致密性差;与WS_(2)薄膜相比,Ti/WS_(2)复合薄膜的晶粒尺寸减小,组织变得致密,掺杂镧后薄膜的晶粒尺寸进一步减小,组织更致密;镧的掺杂还降低了薄膜中硫与钨的原子比,增加了硬质钨相的相对含量,提高了薄膜的硬度和变形抗力。

磁控溅射制备Al-Cu合金薄膜的纳米压痕力学性能与强化机制

采用磁控溅射方法在不锈钢表面制备了铜原子分数在0~11.8%的Al-Cu合金薄膜,研究了铜含量对薄膜微观结构、纳米压痕力学性能和强化机制的影响。结果表明:纯铝薄膜呈现面心立方结构,铜原子分数在2.2%~6.5%时Al-Cu合金薄膜均形成过饱和固溶体相,当铜原子分数超过6.5%后,薄膜中生成了AlCu化合物。随铜含量的增加,薄膜的晶粒尺寸减小,硬度和弹性模量增加,当铜原子分数增至11.8%时,晶粒尺寸为34.7 nm,硬度和弹性模量分别比纯铝薄膜提高了212.5%,2.2%;当铜原子分数在0~6.5%时薄膜的强化主要来自于细晶强化和固溶强化,当铜原子分数超过6.5%后,薄膜的强化是细晶强化、固溶强化和第二相强化共同作用的结果。

Mechanical properties of tungsten nanowhiskers characterized by nanoindentation

The Mechanical properties of the hexagonal tungsten nanowhiskers, which were synthesized by chemical vapor deposition, were characterized by instrumented nanoindentation and atomic force microscope （AFM）. The nanoindentation results show that tungsten nanowhiskers exhibit a hardness of （6.2±1.7） GPa and an elastic modulus of （225±20） GPa. According to the comparative test results, the tungsten nanowhiskers possess a comparable hardness to tungsten microwhiskers, and an hardness increase of 35% to the bulk single-crystal tungsten. The increase in the hardness of whiskers is attributed to the lacking of dislocation avalanche observed in the bulk single-crystal tungsten. The measured modulus is about 80% that of the tungsten microwhiskers, which can be contributed to the size effects of the nanowhiskers and the substrate effects in the nanoindentation test.

Microscopic mechanical characteristics analysis of ultranano-crystalline diamond films

The microscopic mechanical characteristics of ultranano-crystalline diamond films which were prepared in four different atmospheres were investigated for the applications in microelectron-mechanical system（MEMS）.The loading-unloading curves and the change of modulus and hardness of samples along with depth were achieved through nanoindenter.The results show that the films which are made in atmosphere without Ar have the highest recovery of elasticity,hardness（72.9 GPa） and elastic modulus（693.7 GPa） among the samples.Meanwhile,samples fabricated at a low Ar content have higher hardness and modulus.All the results above demonstrate that atmosphere without Ar or low Ar content leads to better mechanical properties of nanodiamond films that are the candidates for applications in MEMS.

High-throughput determination of mechanical and diffusion properties of Ti–Ta–Fe alloys

The mechanical and diffusion properties of Ti-Ta-Fe alloys in the Ti-rich region were investigated by utilizing a high-throughput method, with the combination of nanoindentation and diffusion couple techniques.Five groups of ternary Ti-Ta-Fe diffusion couples were prepared after annealing at 1273 K for 25 h. The composition-dependent mechanical properties of bcc Ti-Ta-Fe system were experimentally determined by means of nanoindentation and electron probe microanalysis(EPMA) techniques. Moreover, the interdiffusion coefficients of Ti-Ta-Fe alloys at 1273 K were confirmed from the composition gradients of the ternary diffusion couples with the support of a pragmatic numerical inverse method. A composition-dependent database on the mechanical and diffusion properties of Ti-Ta-Fe alloys was carefully established and utilized for the discussion of the processability during the hot working. The results indicated that the content of Fe should be controlled for the Ti alloys with high hardness and low Young’s modulus.

Mechanical properties of AISI 1045 ceramic coated materials by nano indentation and crack opening displacement method

Abstract： An effective approach was conducted for estimating fracture toughness using the crack opening displacement （COD） method for plasma enhanced chemical vapor deposition （PECVD） coating materials. For this evaluation, an elastoplastic analysis was used to estimate critical COD values for single edge notched bending （SENB） specimens. The relationship between fracture toughness （Kic） and critical COD for SENB specimens was obtained. Microstructure of the interface between AleO3-TiO2 composite ceramic coatings and AISI 1045 steel substrates was studied by using scanning electron microscope （SEM）. Chemical compositions were clarified by energy-dispersive X-ray spectroscopy （EDS）. The results show that the interface between of Al203-TiO2 and substrate has mechanical combining. The nanohardness of the coatings can reach 1 200 GPa examined by nanoindentation. The Klc was calculated according to this relationship from critical COD. The bending process produces a significant relationship of COD independent of the axial force applied. Fractographic analysis was conducted to determine the crack length. From the physical analysis of nanoindentation curves, the elastic modulus of 1045/AI2O3-TiO2 is 180 GPa for the 50 μm film. The highest value of fracture toughness for 1045/A1203-TiO2-250 μm is 348 MPa·mv2.

Mechanical properties of Cu matrix composite fabricated by extrusion process

Carbon nanotube （CNT）was applied in various fields for itssuperior electrical, mechanical and thermal characteristics. After composites were fabricated by extrusion processusing ball-milledCu-CNT powders, mechanicalpropertiesofCu-CNT composites according to CNT fraction were reviewed. CNT （1%, 5% and 10%）,Cu （d=100 nm）, zirconia balls （90 g） and ethanol （20mL） were mixed and dispersed for5h at a speed of 500 r/minusing a planetary ball mill. A billet （d=50 mm, length=100 mm） was made with Cu, and the composite powderswerefilled up into billet using the uni-axial press. In the extrusion process, after the billet was heated at 880℃for1h, specimens were produced in the shape of a round bar using the billet by applying a load of 200 t. The composite powdersweremeasured for particle size byparticlesize distributionequipment. Then the specimen surface fabricated by extrusion was observed by SEM. Mechanicalpropertiesmeasured by the indentation equipment increased with increasing CNT content. The yield strength, tensile strength and hardness of theCu–CNTs composites canbeobviously improved.