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Cf/SiC composite and Ti alloy (TC4) were successfully joined by the mixed powders of Ag, Al, Ti and short carbon fibres under vacuum condition. The Microstructure of the joints was investigated by X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry. The results show that the good chemical bonding and reactive composite brazing joints are obtained by reactive composite brazing with both (Ag-6Al)+Ti and (Ag-6Al)+Ti+C filler materials. The addition of short carbon fibres contributes a lot to the shear strength by alleviating the thermal stress of the joints and to the in situ synthesised TiC which surround the uniformly distributed short carbon fibres. Ti element can improve filler metal's wettability to Cf/SiC composite and restrain the oxidation of Al element. The max shear strength obtained is 90·8 MPa and the optimal parameter is brazing at 910°C within 10 min. [ABSTRACT FROM AUTHOR]

Uniaxial hot tensile tests were carried out in order to investigate the superplastic deformation of laser welded Ti-6Al-4V sheet. The results revealed that the welded specimens had good superplasticity at temperature of 870-920°C and strain rate of 10-3-10-2 s-1, and the elongation was 233-397%. Dynamic globularisation was observed in the weld bead, and the acicular structure of weld bead was transforming into equiaxed grains while straining. The increasing temperature and decreasing strain rate enhanced the globularisation process. [ABSTRACT FROM AUTHOR]

Carbon fibre reinforced SiC (Cf/SiC) was successfully joined to Ti alloys with Cu-Ti-C mixed powder by brazing. Microstructures of the brazed joints were investigated by SEM, EDS and XRD. The mechanical properties of the brazed joints were measured by a mechanical testing machine. The results showed that the performed joints have dense bonding layers reinforced by residual graphite and in situ synthesised TiC from the reaction of C and Ti in the bonding layers. The composite brazing layers relaxed the thermal stress of the joints effectively. These characteristics were beneficial to the joints, of which the shear strength was remarkably higher than the optimal shear strengths of the joints brazed with pure Cu-Ti. [ABSTRACT FROM AUTHOR]

The diffusion of atoms and the growth behaviour of intermetallic compounds (IMCs) at both Sn–3·5Ag–0·5Cu/Cu and 63Sn–37Pb/Cu interfaces under isothermal aging and thermal shearing cycling conditions have been investigated. The results show that a Cu6Sn5 IMC layer is formed at both the Sn–Ag–Cu/Cu and Sn–Pb/Cu interfaces, and the morphology of Cu6Sn5 changes gradually from scallop structure to plate-like structure with increasing number of thermal shearing cycling, while two IMCs, Cu6Sn5 and Cu3Sn, are formed at the Sn–Ag–Cu/Cu and Sn–Pb/Cu interfaces after isothermal aging for 100 h. The IMC growth follows parabola growth kinetics, implying that the IMC growth is controlled by the diffusion of Cu atoms. In Sn–Ag–Cu solder, Ag3Sn, forming uniform particles after reflowing, congregates gradually to be chunk-like. [ABSTRACT FROM AUTHOR]

Transient liquid phase diffusion bonding of SiC particulate reinforced 2618 aluminium alloy matrix composite (SiCp/2618Al MMC) was carried out by using interlayers of mixed Al–Ag–Cu and Al–Ag–Cu–Ti powders. The effects of Ti on formation, microstructure and properties of the joints were investigated. The results show that adding a certain amount of Ti can obviously improve the TLP bonding quality of SiCp/2618Al MMC by using an Al–Ag–Cu interlayer with the eutectic composition. Besides improving the wettability of Al–Ag–Cu eutectic liquid to surfaces of the parent materials during bonding, the Ti added into interlayers has an effect of shortening the solidification time of the joining layer, thus decreasing SiC particles from the parent materials entering into the joining layer. The joints bonded using Al–Ag–Cu–Ti interlayers have a maximum shear strength of 101 MPa when 2·1%Ti is added. [ABSTRACT FROM AUTHOR]

Mixed Al–Si, Al–Si–SiC and Al–Si–W powders were employed as insert layers to reactive diffusion bond SiCp/6063 metal matrix composites (MMC). The results show that using mixed Al–Si–SiC powder as insert layers, SiCp/6063 MMC can be reactive diffusion bonded by a composite joint. Because of the SiC segregation, however, there are a number of porous zones in the joining layer, which result in the low shear strength of the joints reactive diffusion bonded by the insert layer of mixed Al–Si–SiC powder, even lower than those bonded by the insert layer of mixed Al–Si powder. The Ti added in the insert layer obviously improved the joint strength of the mixed Al–Si–SiC powder. Nearly all the W added into the insert layer of Al–Si–W reacts with Al to form intermetallic WAl12 during bonding. The reaction between the W and Al facilitates the formation of a dense joint of high quality, in addition the WAl12 has a reinforcing effect on the joints, which enables the joints bonded by the insert layer of mixed Al–Si–W powder to have a high shear strength. [ABSTRACT FROM AUTHOR]

A mixture of ferrotitanium and sucrose was heated to carbonise the sucrose, so the ferrotitanium particles were bound by the carbon obtained from the pyrolysis of sucrose. Then a Fe-Ti-C composite powder was made for reactive thermal spraying, which could avoid separation of Ti and C during spraying. The carbon is a reactive constituent as well as the binder in the composite powder. While this powder was used to deposit cermet coating by plasma spraying, a mass of TiC particles were in situ synthesised and uniformly distributed within metallic matrix. Average microhardness and surface hardness of the TiC-Fe coating are about 1672·5 HV0·2 and 91·4 HR(15 N) respectively. Adhesive strength value of the coating reaches 61·86 MPa. Finally, the cermet coating has good wear resistance performance. [ABSTRACT FROM AUTHOR]

Ni50·9Ti49·1 specimens were heat treated using a thermal simulator. The martensitic transformation behaviours of selected areas of the thermal simulating treated specimens were studied with resistivity temperature measurements. In the thermal simulating process specimens were heated by a large electric current to a given peak temperature (400, 500, 600, 800, 900 or 1100°C respectively) and immediately water cooled to room temperature. As the two ends of a NiTi alloy specimen were fixed in copper jigs, unequal heat treatment effect areas were formed in the specimen segments near its two ends. In the unequal area of an 800°C thermal simulating treated sample, a wide transformation temperature range phenomena appeared. The experimental results indicate that non-equilibrium heat treatment proves to be an effective method to fabricate transformation temperature gradient shape memory materials. [ABSTRACT FROM AUTHOR]