Surface effects of hybrid vibration-assisted femtosecond laser system for micro-hole drilling of copper substrate

The ultrafast laser based hybrid machining system was studied and a novel approach was demonstrated to improve laser machining quality on metals by vibrating the optical objective lens with a low frequency (500 Hz) and various displacements (0-16.5 μm) during a femtosecond laser machining process.The laser used in this experiment is an amplified Ti:sapphire femtosecond (10-15 s) laser system that generates 100 femtosecond pulses having an energy of 3.5 mJ/pulse with a 5 kHz repetition rate at a central wavelength of 790 nm.It is found that both the wall surface finish of the machined structures and the aspect ratio obtained using the frequency vibration assisted laser machining are improved compared with those derived via laser machining without vibration assistance.     

Effect of pulse time on surface characteristics and corrosion resistance during pulse electrochemical polishing

Pulse electrochemical polishing (PECP) was used to improve the mechanical properties,such as surface roughness and corrosion resistance,of conductive metallic materials.PECP can provide a smooth,bright,reflective,and deburred surface that exhibits superior corrosion resistance.In this work,stainless steel was used as the anode,and copper was used as the cathode due to their low electrical resistances.The surface roughness of the PECP sample was measured by atomic force microscopy (AFM).A scanning electron microscope (SEM) was used to observe surface characteristics,and an Auger electron spectroscope (AES) was used to analyze the metallurgical composition and thickness of the passive film.The aim of this research was to compare the corrosion resistance rates of the unprocessed and PECP-processed stainless steel.     

Evaluation of microstructure and mechanical properties of Mg-xCe-0.5Zn alloys by nano-indentation

The microstructure and mechanical properties of Mg-xCe-0.5Zn(x=0.5,1.5,2.5,molar fraction,%) alloys were examined using a nano-indentation technique.The alloys were fabricated using a vacuum induction melting method under an argon atmosphere. The microstructures of Mg-xCe-0.5Zn alloys mainly consist ofα-Mg and eutectic Mg12Ce phase.The volume fraction and size of the eutectic Mg12Ce phase increase with increasing Ce contents.Nano-indentation test results show that the indentation hardness and elastic modulus of the eutectic Mg12Ce phase are higher than those of theα-Mg matrix.In addition,the mean indentation hardness and elastic modulus of the Mg-xCe-0.5Zn alloys increase with the Ce addition amount increasing.     

Influence of alloying elements on microstructure and microhardness of Mg-Sn-Zn-based alloys

The phase evolution in （88%-91%）Mg-8%Sn-l%Zn-X （X=A1, Mn and/or Ce） system was analyzed via CALPHAD method and simulations were used in precise selection of the chemical composition. The influence of the addition of different alloying elements such as A1, Mn and Ce on the microstructure and microhardness of Mg-8%Sn-l%Zn-based alloys was investigated. Combined addition of A1 and Mn shows features distinct from separate addition of A1 or Mn. Additions of l%AI and l%Mn to base alloy result in the formation of massive A1-Mn phase in a-Mg matrix grains. Addition of Ce element can refme the second eutectic precipitates and form intermetallic compounds with Sn. Fine rod-like Sn-Ce phase presents mainly on the grain boundaries and plays a role in inhibiting grain growth. The effects of alloying elements on Vickers microhardness and indentation size effect of base alloy were examined.     

钛沉积工艺制备TiN/cBN和TiC/金钢石涂层颗粒(英文)

用钛熔盐沉积及热处理工艺分别制备碳化钛涂覆的立方碳化硼颗粒(TiN/cBN)及碳化钛涂覆的金刚石颗粒(TiC/金刚石)。将cBN或金刚石颗粒分别与钛粉和KCl、NaCl和K2TiF6熔盐混合。将所得混合物在Ar气氛中加热至900°C,然后在H2气氛中于1000°C进行热处理。采用扫描电镜、X射线衍射和聚焦离子束技术对所制得颗粒进行表征。结果表明:cBN和金刚石颗粒表面已覆盖了纳米钛层。对Ti/cBN和TiC/金刚石涂层颗粒进行热处理后,颗粒表面沉积的Ti层与cBN和金刚石颗粒发生了原位化学反应,分别转化为钛化合物TiN和TiC。     

船用5052-O铝合金在海水中的力学和电化学性能(英文)

采用电化学实验和SEM表面形貌观察,对船用5052-O铝合金在海水中的腐蚀保护电位进行优化,以克服诸如点蚀、腐蚀、应力腐蚀开裂和氢脆等行为的发生。在外加电流阴极保护的条件下,最优的保护电位范围为-1.3V～-0.7V。在此电位下,试样的腐蚀电流密度较低,经恒电位实验后,试样表面形貌保持得较好。     

Linear Heating Rate Affects Gelation of Alaska Pollock and Pacific Whiting Surimi

Shear stress of Alaska pollock surimi gels with and without beef plasma protein (BPP) increased as heating rate decreased, but shear strain was unaffected. An increase in shear stress was accompanied by an increase of cross-linked myosin heavy chain. Slow heating rates increased proteolysis in Pacific whiting surimi as shown by degradation of myosin heavy chain and low shear stress and shear strain. Proteolysis of whiting surimi was lessened by BPP to a greater extent at rapid heating rates (20 and 30°C/min) than at slow heating rates (1 and 5°C/min).