Meslet Al-Hajri

The tensile response and fracture behavior of 2009 aluminum alloy metal matrix composite

Abstract In this research paper the tensile properties and fracture characteristics of aluminum alloy 2009 discontinuously reinforced with silicon carbide particulates (SiC p ) are presented and discussed. The increased strength of the Al 2009/SiC p composite is attributed to the synergistic influences of residual stresses generated due to intrinsic differences in thermal expansion coefficients between the composite constituents, strengthening from constrained plastic flow and triaxiality in the ductile aluminum alloy metal matrix due to the presence of ceramic particle reinforcements. Fracture on a microscopic scale comprised of cracking of the individual and clusters of SiC particles present in the microstructure. Final fracture of the composite resulted from crack propagation through the matrix between the clusters of reinforcing SiC particles. The key mechanisms governing the tensile fracture process are elucidated.

Influence of titanium dioxide nanopowder addition on microstructural development and hardness of tin–lead solder

Abstract This paper presents the microstructure and hardness of composite solders obtained by the addition of nanopowders of titanium dioxide to a conventional solder. Titanium dioxide powders-reinforced lead (Pb)–tin (Sn) composite solders were prepared by thoroughly blending nano-sized titanium dioxide powders with powders of a eutectic solder and using a water-soluble flux. The blended solder paste was melted and allowed to re-solidify in a crucible placed on a hot plate and maintained at a constant temperature. Optical microscopy observations revealed that for additions of titanium dioxide up to 1 wt.%, the grain size and width of the grain boundary decreased. For the addition of 2 wt.% of titanium dioxide, nanopowders microporosity was observed both at and along the grain boundary regions coupled with the presence of second-phase particles. Microhardness measurements revealed that the addition of titanium dioxide nanopowders is helpful in enhancing the overall strength of the eutectic solder.

The influence of copper nanopowders on microstructure and hardness of lead-tin solder

Abstract This paper presents the microstructure and hardness of composite solders obtained by the addition of nanopowders of copper to a conventional solder. Copper powders-reinforced lead (Pb)–tin (Sn) composite solders were prepared by thoroughly blending nano-sized copper powders (average powder particle size 100 nm) with a powder of a eutectic solder and using a water-soluble flux. The blended solder paste was melted and allowed to re-solidify in a crucible placed on a hot plate and maintained at a constant temperature. Optical microscopy observations revealed the as-solidified microstructure of the composite solder to be altered by the addition of nanopowders to the eutectic Sn–Pb solder. The copper powders precipitated as intermetallic compounds that were non-uniformly distributed through the microstructure. Microhardness measurements revealed a 30–40% increase in hardness of the composite solder over the conventional unreinforced eutectic counterpart.

Influence of silicon carbide particulate reinforcement on quasi static and cyclic fatigue fracture behavior of 6061 aluminum alloy composites

In this paper, the quasi-static and cyclic fatigue fracture behavior of aluminum alloy 6061 discontinuously-reinforced with fine particulates of silicon carbide are presented and discussed. The discontinuous particulate-reinforced 6061 aluminum alloy was cyclically deformed to failure at ambient temperature under stress-amplitude controlled conditions. The influence of volume fraction of particulate reinforcement on high cycle fatigue response is presented. The underlying mechanisms governing the fracture behavior during quasi-static and cyclic fatigue deformation are discussed and rationalized in light of concurrent and mutually interactive influences of composite microstructural features, deformation characteristics of the metal matrix and reinforcement particulate, nature of loading and ductility of the microstructure.

The fatigue and final fracture behavior of SiC particle reinforced 7034 aluminum matrix composites

Abstract In this research paper, the cyclic stress-amplitude-controlled fatigue response and fracture behavior of aluminum alloy 7034 discontinuously reinforced with silicon carbide particulates (SiCp) is presented. In view of the limited ambient temperature ductility, test specimens of the 7034/SiCp composite, in both the under-aged and peak-aged conditions, were cyclically deformed under stress-amplitude-control at an elevated temperature corresponding to the aging temperature of the alloy. The cyclic fatigue tests were conducted at two different load ratios with the objective of documenting the conjoint influences of intrinsic composite microstructural effects, nature of loading, and magnitude of cyclic stress amplitude on cyclic fatigue life and fracture characteristics. The final fracture behavior of the composite is discussed in light of the concurrent and mutually interactive influences of composite microstructural effects, deformation characteristics of the composite constituents, nature of loading, and resultant fatigue life.

Cyclic plastic strain response and fracture behavior of 2009 aluminum alloy metal-matrix composite

Abstract A study has been made to understand the role of composite microstructure on failure through mechanisms governing the quasi-static and cyclic fracture behavior of aluminum alloy X2080 discontinuously-reinforced with silicon carbide (SiC) particulates. Two different volume fractions of the carbide particulate reinforcement phase, in the aluminum alloy matrix, are considered. Quasi-static fracture of the composite comprised cracking of the individual and clusters of particulates present in the microstructure. Particulate cracking increased with reinforcement content in the aluminum alloy matrix. Final fracture occurred as a direct result of crack propagation through the matrix between particulate clusters. The composite specimens were cyclically deformed under fully-reversed, total strain-amplitude-controlled cyclic straining, giving lives of less than 10 4 cycles to failure. The plastic strain-fatigue life response was found to degrade with an increase in carbide particulate content in the metal matrix. The cyclic fracture behavior of the composite is discussed in light of concurrent and mutually interactive influences of composite microstructural effects, matrix deformation characteristics, cyclic plastic strain amplitude and resultant response stress.

Influence of heat treatment on tensile response of an oxide dispersion strengthened copper

In this paper, the influence of heat treatment on tensile properties and fracture characteristics of dispersion strengthened copper is examined. Heat treating the alloy in the as-drawn condition was found to have little influence on grain structure and intrinsic microstructural features. The strength of the material decreases with heat treatment with a concomitant improvement in ductility. The material maintains a high value of yield strength retention ratio. The influence of heat treatment on tensile properties and fracture characteristics is detailed.

The tensile deformation, cyclic fatigue and final fracture behavior of dispersion strengthened copper

Abstract The tensile deformation, cyclic stress response characteristics, cyclic stress–strain response, cyclic strain resistance and fatigue properties of an oxide dispersion strengthened copper alloy were studied over a range of cyclic plastic strain–amplitudes. The specimens were cycled using tension-compression loading under total strain–amplitude control. In the as-drawn condition, the dispersion strengthened copper alloy displayed continuous softening to failure at all cyclic plastic strain amplitudes. The rolled plus heat-treated microstructure displayed initial hardening followed by rapid softening to failure. The strain–fatigue life relationship is predicted using the parameters obtained from the fatigue test. Potential mechanisms controlling the stress response and concomitant cyclic strain resistance and cyclic fatigue life are also evaluated, and rationale for observed behavior is discussed in light of concurrent and interactive influences of initial state of the matrix dislocation arrangement, magnitude of cyclic strain amplitude, response stress and intrinsic microstructural effects.

Effect of Particulate Silicon Carbide on Cyclic Plastic Strain Response and Fracture Behavior of 6061 Aluminum Alloy Metal Matrix Composites

In this paper, the cyclic stress response and cyclic stress–strain response characteristics, cyclic strain resistance and low-cycle fatigue life, and mechanisms governing the deformation and fracture behavior of aluminum alloy 6061 discontinuously reinforced with silicon carbide (SiC) particulates are presented and discussed. Two different volume fractions of the carbide particulate reinforcement phase in the aluminum alloy metal matrix are considered. The composite specimens were cyclically deformed using fully reversed tension–compression loading under total strain-amplitude-control. The stress response characteristic was observed to vary with strain amplitude. The plastic strain-fatigue life response was found to degrade with an increase in carbide particulate content in the metal matrix. The fracture behavior of the composite is discussed in light of the interactive influences of composite microstructural effects, cyclic strain amplitude and concomitant response stress, deformation characteristics of the composite constituents and cyclic ductility.

Influence of temperature on impact fracture behavior of an alloy steel

Abstract In this paper, the influence of temperature on impact toughness and fracture behavior of alloy steel (AISI Classification 8320) is presented and discussed. Impact toughness decreased with a decrease in test temperature. The extrinsic influence of temperature on impact toughness–fracture resistance relationships is rationalized in light of the conjoint and mutually interactive influences of intrinsic microstructural features, local stress states and macroscopic fracture behavior.