Influence of Welding Process on Microstructure and Properties of Laser Welding of SiCp/6061 Al Matrix Composite

Direct laser welding, laser welding with Ti interlayer, and ultrasonic-assisted laser welding with Ti interlayer were used to join SiCp/6061 Al matrix composites. Microstructural evolutions, compositional distributions and tensile strengths under three processes were compared and analyzed. The experimental results showed that ultrasonic-assisted laser welding with Ti interlayer can obtain joints with good continuity and without obvious defects. Due to combined effects of Ti interlayer and ultrasonic, formation of brittle Al4C3 phase was greatly suppressed and fine TiC precipitates were also uniformly distributed in weld metal. The strength shown by the welded joints could reach up to 77.2% of the strength of the base material. Because of the internal defects (voids and pores) and the generated large numbers of brittle phases of Al4C3 in weld metal, the joint strength shown by the other two techniques, direct laser welding and laser welding with Ti interlayer, only reached 49.4 and 64.8% of the base material strength, respectively.

Evolution of Microstructure, Texture and Mechanical Properties for Multilayered Al Matrix Composites by Accumulative Roll Bonding

Carbon nanotubes (CNTs) reinforced aluminum matrix nanocomposites were fabricated by Accumulative Roll Bonding (ARB). The surface morphologies, mechanical properties, grains texture and orientation of the Al/CNTs nanocomposites were characterized, and the mechanisms and influences of CNTs contents and ARB cycles on the mechanical performance and grain textures of Al/CNTs were investigated and revealed. The strength of the composites rose with increase of the CNTs content, and the ARB cycles showed a 26% improvement when the CNTs content varied from 0 to 1 volume percent (vol.%). The increase in the mass fraction of the carbon nanotubes made the grain distribution in the Al/CNTs nanocomposite samples more diffuse. Besides, the stable texture of the hot rolled crystal grains on the α orientation are constantly turning to {011}< 011> with the mass fraction of the reinforcing phase increased.

Study on the Microstructure and Wear Behavior of In-Situ Al3Ti/Al Composites Under Induction Heating

In the study, Ti fiber (200 μm, 99.8 wt.%) and pure aluminum (99.6 wt.%) were respectively used as the reaction source and matrix to prepare Al-based composites by in-situ synthesis methods. During the stage of preparing the preform, Ti fibers were fixed in the matrix at equal intervals to pre-control the initial position of the product. The preform was heated in an induction heating device finally, at the same time, parameter combinations of different frequencies and currents were applied to promote the in-situ reaction between Al-Ti, thereby the Al matrix composites reinforced by Al3Ti were obtained. The phase composition, microstructure and wear resistance of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and wear testers. The results show that when the frequency and current are 5 kHz and 15 A respectively, the Ti fiber is completely reacted, and the product is the isometric Al3Ti with a size of 1 – 2 μm and a particle spacing of about 5 μm, reaching the optimal microstructure under all parameters. Under the condition of a load of 9.8 N, the wear rate of the composites at 5 kHz and 15 A is 2.325 mg/mm2, indicating the best values in this experiment.

Spark Plasma Sintering of AlN/Al Functionally Graded Materials

In this paper, six-layer AlN/Al gradient composites were prepared by a spark plasma sintering process to study the influences of sintering temperature and holding time on the microstructure and mechanical properties. The well-bonded interface enables the composite to exhibit excellent thermal and mechanical properties. The hardness and thermal expansion properties of the composite exhibit a gradient property. The hardness increased with the volume fraction of AlN while the CTE decreased as the volume fraction of AlN. The thermal expansion reaches the lowest value of 13–14 ppm/K, and the hardness reaches the maximum value of 1.25 GPa, when the target volume fraction of AlN is 45%. The simulation results show that this gradient material can effectively reduce the thermal stress caused by the mismatch of the thermal expansion coefficient as a transmitter and receiver (T/R) module. This paper attempts to provide experimental support for the preparation of gradient Al matrix composites.

Corrosion of Aluminum Metal Matrix Composites: A Review of the Effect of Manufacturing Processes, Processing Routes and Secondary Phases

The vulnerability of Al matrix composites to general and preferential corrosion is due to the intrinsic proneness of binary materials to undergo advanced deterioration. Control of the prevalent sites for evolution and proliferation of confined corrosion strongly influence the corrosion resistance of the composites. The problem for enhanced utilization of composites, has exacerbated with attention on the productive life and resilience to environmental degeneration during operational service. This can be achieved through proper comprehension of the electrochemical mechanism, the intriguing nature of SiC grains and their importance on the secondary phases, metallurgical configuration, and manufacturing process routes. This review confirms the relevance of secondary phases, microstructures and manufacturing processes in relation to SiC particles on the corrosion invulnerability of Al matrix composites to further add corrosion mitigation in design and and technological advancement.