Search

Aluminum matrix composites (AMCs) reinforced with the nano‐sized particles are very important materials for the applications in industrial fields. These aluminum matrix composites consist of an aluminum matrix and nano‐sized particles, which own very different physical and mechanical properties from those of the matrix. Nano‐sized particles show a more obvious strengthening effect on the matrix than the micro‐sized particles do, because of the high specific surface area which is positive for the pinning effect during the deformation process. Thus, the nano‐sized particle‐reinforced AMCs usually exhibit a good ductility. The main issues of the fabrication methods are the low wettability between the nano‐sized particles and the molten aluminum alloys, which is fatal to the conventional casting methods, and the agglomeration of nano‐sized particles which happened easier than the larger particles. Several alternative processes have been presented in literature for the production of the nano‐sized particle‐reinforced aluminum composites. This paper is aimed at reviewing the feasible manufacturing techniques used for the fabrication of nano‐sized particle‐reinforced aluminum composites. More importantly, the strengthening mechanisms and models which are responsible for the improvement of mechanical properties of the nano‐sized particle‐reinforced aluminum composites have been reviewed. [ABSTRACT FROM AUTHOR]

In the present work, the tensile properties at 77 K of the 0.3 wt% nano‐sized TiCp/Al–Cu composite is investigated to explore its potential application at cryogenic temperature. The TiCp/Al–Cu composite exhibits superior ultimate tensile strength (620 MPa), yield strength (531 MPa), and fracture strain (7.2%) at 77 K. The addition of TiCp leads to the refinement of θ′ precipitates and enhanced dislocation strengthening effect, contributing to the improved tensile strength. [ABSTRACT FROM AUTHOR]

A sandwich structure laminate composed of a ductile 2014Al inter-layer and two nanoscale SiC reinforced 2014Al (SiC/2014Al) composite outer layers was successfully fabricated through the combination of powder metallurgy and hot rolling. The ductile 2014Al inter-layer effectively improved the processability of the sandwiched laminates. Tensile test revealed that the yield strength and ultimate tensile strength of the sandwiched laminate were 287 and 470 MPa, respectively, compared with 235 and 425 MPa for monolithic 2014Al. The good performance of the sandwiched laminate results from the strong bonding between the SiC/2014Al composites layer and the ductile 2014Al layer. Thus, the sandwich structure with a composite surface and ductile core is effective for increasing the strength and toughness of composite laminates. [ABSTRACT FROM AUTHOR]

Abstract A novel Mg-8Al-2Sn-1Zn alloy with a bimodal structure prepared by hard-pate-rolling (HPR) exhibits both higher tensile strength and ductility than its fine-grained counterparts prepared by conventional rolling. By delicate electron back-scatter diffraction (EBSD) analysis, we found fine grains with weak basal texture is beneficial for basal slip and favors initial deformation. Meanwhile, coarse grains with a strong basal texture could accommodate abundant newly generated dislocations, promoting work hardening after fine grains are saturated with dislocations. For the first time, individual roles of fine and coarse grains and their synergy effect on enhancing ductility in bimodal structured Mg alloys is clarified. Graphical abstract Image 1 Highlights • A bimodal grain-structured Mg alloy is fabricated by hard-pate-rolling. • The bimodal sample has higher strength and ductility than fine-grained samples. • The synergy effect of fine and coarse grains on enhancing ductility is clarified. [ABSTRACT FROM AUTHOR]

Abstract In situ TiC p /Al-Cu-Mg-Si nanocomposites were prepared in Al-Ti-C systems with different carbon sources (pure carbon black, mixed carbon source (50 wt% CNTs + 50 wt% carbon black) and pure CNTs) via a combination of the combustion synthesis, hot press and hot extrusion methods. The in situ TiC p /Al-Cu-Mg-Si nanocomposites synthesized by the mixed carbon source obtained the most uniform distribution of nanosized TiC p , highest yield strength (σ 0.2) and tensile strength (σ UTS) and best fracture strain (ε f). The 30 vol% TiC p /Al-Cu-Mg-Si nanocomposite synthesized by the mixed carbon source showed superior σ 0.2 (217 MPa), σ UTS (251 MPa), and ε f (17.7%) at 533 K, which were respectively 4.3%, 4.1% and 136% higher than those of the nanocomposite synthesized by pure C black (208 MPa, 241 MPa and 7.5%) and respectively 3.8%, 1.6% and 88.3% higher than those of the nanocomposite synthesized by pure CNTs (209 MPa, 247 MPa and 9.4%). The superior high-temperature tensile strength and ductility of the nanocomposites prepared by the mixed carbon source were attributed to the homogeneous distribution of nanosized TiC p. The strengthening of the nanosized TiC p and θ′ precipitates was the main strengthening mechanism of the in situ TiC p /Al-Cu-Mg-Si nanocomposites at high temperatures. Highlights • In situ TiC p /Al nanocomposites are prepared in Al-Ti-C systems with various carbon sources. • Nanocomposites prepared by mixed C/CNTs show the best dispersion of nanosized TiC p. • Nanocomposites prepared by mixed C/CNTs show the best strength and ductility at 493 K and 533 K. [ABSTRACT FROM AUTHOR]

The Al-Cu-Mg-Si matrix composites reinforced with in situ hybrid-sized TiC x -TiB 2 particles with sizes ranging from 20 nm to 1.3 µm were successfully synthesized using the Al-Ti-B 4 C reaction system via a method that combined the combustion synthesis and the hot press assisted with hot extrusion. The sizes of the fabricated TiC x and TiB 2 particles increased with increasing TiC x -TiB 2 content. The hybrid-sized TiC x -TiB 2 particles improved the elevated-temperature yield strength ( σ .2 ), the tensile strength ( σ UTS ), and the fracture ductility ( ε f ) of the composites at both 493 K and 573 K. The 40 wt% (TiC x -TiB 2 )/Al-Cu-Mg-Si composite exhibited superior σ .2 (141 MPa), σ UTS (164 MPa), and ε f (31.2%) at 573 K, with enhancements of 60.2%, 72.6%, and 22.4% compared to the Al-Cu-Mg-Si matrix alloy (88 MPa, 95 MPa, and 25.5%). The improvement of the elevated-temperature mechanical properties for the in situ (TiC x -TiB 2 )/Al-Cu-Mg-Si composites was attributed primarily to the strengthening effects induced by the hybrid-sized TiC x -TiB 2 particles and the θ′ precipitation strengthening. [ABSTRACT FROM AUTHOR]

The bimodal-sized (micron+nano) TiC p /Al-Cu composites were successfully fabricated by adding the in situ micron-sized and nano-sized TiC p -Al master alloys into the molten Al-Cu alloy. The composites reinforced with bimodal-sized TiC p exhibited finer α-Al grains and smaller θ′ precipitates, and possessed enhanced room- and high-temperature strength and relatively high ductility compared with the Al-Cu matrix alloy and their counterparts reinforced with monomodal-sized TiC p . The improved tensile properties may be attributed to the more significant precipitation strengthening due to the smaller θ′ precipitates, grain refinement and strengthening effects of the nano-sized and micron-sized TiC p . [ABSTRACT FROM AUTHOR]

A design map in regard to the generalized-stacking fault (GSF) energy is plotted for Ti 5 Si 3 (Ti 60 Si 36 ) alloying with 12 ternary elements in { 1 1 ¯ 00 } [ 0001 ] slip system. Hereinto, alloying elements occupy preferable Ti sites near slip planes. The elements with a larger radius difference from Ti tend to reduce the GSF energies more dramatically. Moreover, the elements smaller than Ti are more prone to decreasing GSF energies than those larger than Ti. Accordingly, the addition of ternary elements, like Ni, Cu and Co, will lead to an obvious decrease in GSF energies by 18.0%, 16.7% and 13.4% respectively, and therefore may facilitate the initiation of prismatic stacking faults and furthermore enhance ductility. Note that the decline of GSF energies is attributed to the weakening covalent bonds between slip planes with the introduction of ternary elements. Our calculations provide a guide to experiments on the design of Ti 5 Si 3 compounds with tailored properties. [ABSTRACT FROM AUTHOR]

Different dendritic grain morphology of an Al-Cu alloy was obtained by adjusting the casting parameters. Compared to the equiaxed dendritic grains, the tortuous dendritic grains led to increased tensile elongation (from 10.4% to 16.8%) and work of fracture (from 11.2 J/mm 2 to 17.2 J/mm 2 ) by more than 50%, respectively. Meanwhile, the high tensile strength (∼540 MPa) and grain size (∼80 μm) were unchanged. The intergranular fracture crack zigzagged along tortuous grain boundaries, reducing the stress concentration at the crack tip and increasing the propagation resistance and path, leading to increased toughness and elongation. The zigzag morphology of grain boundaries was attributed to tortuous dendritic grains. [ABSTRACT FROM AUTHOR]

Adding various amounts of nano-sized TiC p (0.1–0.7 wt%) made a simultaneous improvement in high-temperature strength and ductility of the Al-Cu matrix alloy. The influences of temperature and strain rate on the high-temperature tensile properties and θ′ precipitate sizes in the Al-Cu matrix alloy and the nano-sized TiC p /Al-Cu composites were investigated. Theoretical calculations suggest that the yield strength increment of the composites at 453 K was primarily attributed to the strengthening effect of both the refined θ′ precipitates and TiC p , while at 493 K only the strengthening effect of TiC p was predominant due to the significant coarsening of θ′ precipitates at this temperature. [ABSTRACT FROM AUTHOR]

Achieving bimodal grain structure via cold rolling remains a challenge for Al–Mg alloys. In the present work, a high tensile strength (∼525 MPa) and ductile (∼14%) Al–9Mg alloy was fabricated by a novel hard-plate rolling (HPR) route with a single-pass thickness reduction of 75%. Increasing solute Mg content promotes a bimodal structure and a high dislocation density in the HPRed Al–Mg alloys due to the severely retarding effect of Mg solutes on dynamic recovery/recrystallization. The simultaneous high ductility and strength is due mainly to the strong work hardening ability deriving from the bimodal grain structure and the high solute Mg content. [ABSTRACT FROM AUTHOR]

We report a new rolling route combining one pass of hard-plate rolling and two passes of conventional rolling. This route is efficient in achieving near-spherical Mg 17 Al 12 phase (~0.5 µm) and uniform fine-grained structure (~3 µm) featuring a weakened texture in AZ91-0.4Sn plates after a total thickness reduction of ~86.4% via 3 rolling passes. Moreover, the processed alloy exhibited superplasticity-like fracture strain of ~96% at 200 °C, owing to fine α-Mg grains distributed with a high volume fraction of Mg 17 Al 12 . This new route significantly reduces rolling passes and hence has a great potential for industrial production. [ABSTRACT FROM AUTHOR]

Inspired by nacre, we designed biomimetic metal–ceramic composites in which hard and ductile phases were alternately arranged. We first prepared lamellar-structured TiC scaffolds with 25, 30 and 35 vol% solid loadings using a unidirectional freeze casting technique and then measured wetting and infiltration dynamics for a commercial Al cast alloy, ZL107, with the main composition of Al–7Si–5Cu on the porous TiC scaffold using a modified sessile drop method at 850 °C. The wetting was affected by liquid spreading at horizontal surface and infiltration in depth, while the latter played a dominant role in the decrease in contact angle. On the basis of the wetting results, the lamellar ZL107/TiC composites were successfully fabricated by pressure infiltration of the molten ZL107 alloy into porous TiC scaffolds and their mechanical properties were evaluated. The compressive strength and elastic modulus increased while bending strength decreased with increasing TiC content, giving maximum values of 1166 ± 20 MPa, 205 ± 2 GPa and 363 ± 5 MPa, respectively. Formation of (Al m ,Si 1 − m ) 3 Ti, Al 3 Ti and Al 4 C 3 phases in the composites was presumed to deteriorate the toughness of the composites, leading to brittle fracture under loading. [ABSTRACT FROM AUTHOR]

The tensile properties at elevated temperature of nano-SiC p /Al2014 composites have been investigated. The nano-SiC p can remarkably improve the tensile strength at 493 K of Al2014 alloy without sacrificing the ductility. The strengthening effect for the matrix alloy of 0.5 vol% nano-particles is superior to that of 4 vol% micron-particles. [ABSTRACT FROM AUTHOR]

Abstract: A first-principles method was performed to calculate generalized stacking fault (GSF) energies in Mg alloys with Sn, Pb and Sn+Pb dopings for acting as references of designing Mg–Sn–Pb alloys. We clarify the effect of Sn is dominated than Pb atom on reduced unstable stacking fault energy ( ), especially in basal and pyramidal slip systems. Such a reduction of non-basal slip GSF energy is in favor of improving the ductility of Mg matrix. [Copyright &y& Elsevier]

The effects of doping atoms (X) on the uniaxial deformation and universal ductility of Mg47X1 are investigated. A first-principles “design map” in regard to the generalized stacking-fault energy (GSFE) provides a database for new Mg alloys design. The calculation and analysis of GSFEs here, considering the weighting of each slip system, solubility of alloying elements and ductility capacity, provide a basis for further understanding and controlling alloying elements, which will inspire developing new Mg alloys with tailored properties. [Copyright &y& Elsevier]

Abstract: As-cast Mg–3Al–3Sn (AT33) alloy exhibits strong strain hardening ability, which is illustrated by the very high H c and n values. Decrease in generalized stacking fault (GSF) energies in AT33 alloys by Al and Sn additions facilitates the production of dislocations and activation of deformation twins, causing the accumulation of dislocations at twin boundaries, resulting in a high dislocation density in deformed alloys during tension deformation, which thereby mainly accounts for the strong strain hardening ability. [Copyright &y& Elsevier]

Generalized stacking fault energies of magnesium without and with Al and Sn dopings were studied using first-principles calculations to investigate mechanisms of improved ductility for a new Mg–3Al–3Sn alloy. Reduced unstable stacking fault energy (γus ) results in the improved activity of and the activation of the and slip systems. Moreover, the lower γus of than of leads to the replacement of the latter by the former to be the second primary slip system. [ABSTRACT FROM AUTHOR]

At high temperatures, the weakened strength and decreased ductility of Al alloys limit their industrial applications. (TiB 2 –TiC)/Al–Cu–Mg–Si composites were synthesized by adding in situ dual-phased and bimodal-sized (TiB 2 –TiC)/Al master alloys to molten Al–Cu–Mg–Si alloys. The addition of minor amounts of TiB 2 and TiC particles (0.05 and 0.1 wt%, respectively) effectively refined the α-Al grains and θ′ and Q′ precipitates and increased the elevated-temperature strength and uniform elongation of the Al–Cu–Mg–Si alloys. The 0.1 wt% (TiB 2 –TiC)/Al–Cu–Mg–Si composite showed the best yield strength (279 MPa), ultimate tensile strength (366 MPa), and uniform elongation (10.6%) at 493 K, with enhancements of 9.4%, 15.1%, and 24.7% compared to the Al–Cu–Mg–Si matrix alloy (255 MPa, 318 MPa, and 8.5%). The simultaneous increases in the elevated temperature strength and ductility of the composites were attributed to the strengthening effects of the bimodal-sized TiB 2 and TiC particles, θ′ and Q′ precipitation strengthening, and the refined partial recrystallization microstructure. [ABSTRACT FROM AUTHOR]