Microstructures of explosively consolidated rapidly solidified aluminum and Al-Li alloy powders

The microstructures and the characteristics of water-atomized, nitrogen gas-atomized Al powders and ultrasonic argon gas-atomized Al-Li alloy powder were investigated by means of metallography, SEM, Auger electron spectroscopy and X-ray diffraction techniques. Rapidly solidified powders were explosively consolidated into different sized cylinders under various explosive parameters. The explosively consolidated compacts have been tested and analysed for density microhardness, retention of rapidly solidified microstructures, interparticle bonding, fractography and lattice distortion. It is shown that the explosive consolidation technique is an effective method for compacting rapidly solidified powders. The characteristics of surface layers play a very important role in determining the effectiveness of the joints sintered, and the Al-Li alloy explosive compacts present an abnormal softening appearance compared to the original powder.

Experimental-study on the criteria and mechanism of spallation in an aluminum-alloy

In this paper, a damage function defined by the residual strength of spalled specimens of an aluminium alloy is given to characterize the spallation of the material. Based on this function a simple method for continuously describing the spallation may be developed. Stress wave profiles showing the signal of spallation were successfully obtained with carbon gauges. Microscopic observations of the spalled aluminium alloy specimens reveal that the nucleation of spallation initiates from cracking of the second phase particles. Spallation is a process of crack nucleation, growth and coalescence to final, complete disintegration.

BONDING OF ALUMINA AND METAL USING BULK METALLIC GLASS FORMING ALLOY

Metal-alumina joints have found various practical applications in electronic devices and high technology industry. However, making of sound metal ceramic brazed couple is still a challenge in terms of its direct application in the industry. In this work we successfully braze copper with Al2O3 ceramic using Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass forming alloy as filler alloy. The shear strength of the joints can reach 140 MPa, and the microstructrural analysis confirms a reliable chemical boning of the interface. The results show that the bulk metallic glass forming alloys with high concentration of active elements are prospective for using as filler alloy in metal-ceramic bonding.

Bonding Of Alumina And Metal Using Bulk Metallic Glass Forming Alloy

Metal-alumina joints have found various practical applications in electronic devices and high technology industry. However, making of sound metal ceramic brazed couple is still a challenge in terms of its direct application in the industry. In this work we successfully braze copper with Al2O3 ceramic using Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass forming alloy as filler alloy. The shear strength of the joints can reach 140 MPa, and the microstructrural analysis confirms a reliable chemical boning of the interface. The results show that the bulk metallic glass forming alloys with high concentration of active elements are prospective for using as filler alloy in metal-ceramic bonding.

Development And Characterization Of Composite Ni-Cr-C-Caf2 Laser Cladding On Gamma-Tial Intermetallic Alloy

A process of laser cladding Ni-CF-C-CaF2 mixed powders to form a multifunctional composite coatingd on gamma-TiAl substrate was carried out. The microstructure of the coating was examined using XRD, SEM and EDS. The coating has a unique microstructure consisting of primary dendrite or short-stick TiC and block Al4C3 carbides reinforcement as well as fine isolated spherical CaF2 solid lubrication particles uniformly dispersed in the NiCrAlTi (gamma) matrix. The average microhardness of the composite coatings is approximately HV 650 and it is 2-factor greater than that of the TiAl substrate. (C) 2008 Elsevier B.V. All rights reserved.

Influences Of Precursor Constitution And Processing Speed On Microstructure And Wear Behavior During Laser Clad Composite Coatings On Gamma-Tial Intermetallic Alloy

The effects of constitution of precursor mixed powders and scan speed on microstructure and wear properties were designed and investigated during laser clad gamma/Cr7C3/TiC composite coatings on gamma-TiAl intermetallic alloy substrates with NiCr-Cr3C2 precursor mixed powders. The results indicate that both the constitution of the precursor mixed powders and the beam scan rate have remarkable influence on microstructure and attendant hardness as well as wear resistance of the formed composite coatings. The wear mechanisms of the original TiAl alloy and laser clad composite coatings were investigated. The composite coating with an optimum compromise between constitution of NiCr-Cr3C2 precursor mixed powders as well as being processed under moderate scan speed exhibits the best wear resistance under dry sliding wear test conditions. (C) 2008 Elsevier Ltd. All rights reserved.