The feasibility and parameters optimization of AA5183 aluminum cladding on AISI 1018 steel by electro spark microwelding (ESM) and the corrosion resistance of the clad plate were investigated. The optimum conditions were found as 15 A, 10%, 800 Hz and 2500 rpm for P, D, F and R factors, respectively. Confirmation test under optimum conditions showed that the model can be effectively used to pre...

ÐGamma-TiAl based alloys have recently received attention for potential elevated temperature applications in gas-turbine engines. However, although expected critical crack sizes for some targeted applications (e.g. gas-turbine engine blades) may be less than 0500 mm, most fatigue-crack growth studies to date have focused on the behavior of large (on the order of a few millimeters) through-thick...

When a propagating cleavage front encounters a high-angle grain boundary it first penetrates through the grain boundary stably. With increasing penetration depth the resistance of the grain boundary rises, resulting in the well-known R-curve. When the balance between the rates of the energy release rate and the grain boundary resistance is reached, the crack advance becomes unstable and the gra...

The role of crack-tip shielding in in ̄uencing mixed-mode (mode I‡ II) fatigue-crack growth thresholds for large, through-thickness cracks in a Ti±6Al±4V turbine blade alloy is examined under high-cycle fatigue loading conditions, i.e., at a loading frequency of 1000 Hz in ambient temperature air for load ratios (Kmin=Kmax) of R ˆ 0:1±0.8. Techniques are developed to quantify crack-tip shielding...

The thermal resistance of a bridged matrix crack in a fiber-reinforced ceramic composite is analyzed. The problem is cast in terms of a unit cell comprising an infinitely long composite cylinder with a single matrix crack perpendicular to the fiber axis. At the outset, it is demonstrated that the thermal resistance of such a crack can be represented by a simple circuit consisting of two paralle...

Dense Silicon nitride was investigated to determine the effect of its microstructural parameters and densification on thermo-mechanical properties and thermal stress resistance to fracture initiation during a hot or cold mechanical and thermal shock testing. The different materials and microstructures were obtained by changing the parameters such as the type of the powder, additive, forming p...

Crack tip shielding phenomena, whereby the "effective crack-driving force" actually experienced at the crack tip is locally reduced, are examined with reference to fatigue crack propagation behavior in metals, composites and ceramics. Sources of shielding are briefly described in terms of mechanisms relying on the production of elastically constrained zones which envelop the crack (zone shieldi...

Fatigue crack growth behavior has been examined in a particulate titanium diboride (TiB2)–reinforced iron-based composite that had been produced via a mechanical alloying process. Comparison with equivalent unreinforced material indicated that fatigue crack growth resistance in the composite was superior to monolithic matrix material in the near-threshold regime. The composite exhibited relativ...

Based on the analysis of the crack trapping effect of cleavage ridges and penetration of crack front segments in an iron–silicon alloy, the distance between break-through points along a high-angle grain boundary is investigated. If the break-through points are close to each other, the crack trapping effect is dominant; otherwise, the grain boundary separation in break-through windows governs th...

In this article, the crack growth driving force and the resistance to cleavage cracking associated with crack front transmission across a high-angle grain boundary in a silicon thin film are analyzed, and a closed-form solution of grain boundary toughness is obtained. It is noticed that the fracture resistance of the grain boundary is a function of the film thickness. This size effect is attrib...