This paper presents an attempt to model the stir-welding process using three-dimensional visco-plastic modeling. The scope of the project is focused on butt joints for aluminum thick plates. Parametric studies have been conducted to determine the effect of tool speeds on plate temperatures and to validate the model predictions with available measurements. In addition, forces acting on the tool have been computed for various welding and rotational speeds. It is found that pin forces increase with increasing welding speeds, but the opposite effect is observed for increasing rotational speeds. Numerical models such as the one presented here will be useful in designing welding tools which will yield desired thermal gradients and avoid tool breakage.

Three-dimensional modeling of the friction stir-welding process

Current state of Fe-Mn-Al-C low density steels

https://www.tandfonline.com/doi/pdf/10.1088/1468-6996/14/1/014205

Fe–Al–Mn–C lightweight structural alloys: a review on the microstructures and mechanical properties

Hot corrosion is a serious problem in power generation equipment, gas turbines, internal combustion engines, fluidized bed combustion, industrial waste incinerators and paper and pulp industries. No alloy is immune to hot corrosion attack indefinitely although there are some alloy compositions that require a long initiation time at which the hot corrosion process moves from the initiation stage to the propagation stage. Superalloys have been developed for high-temperature applications. However, these alloys are not always able to meet both the high-temperature strength and high-temperature corrosion resistance simultaneously, so the need to be protected from corrosion. The high-temperature protecting system must meet several criteria, provide adequate environment resistance, be chemically and mechanically compatible with the substrate, be practically applicable, reliable and economically viable. This paper briefly reviews the hot corrosion of some Ni- and Fe-base superalloys to understand the phenomenon. Comprehensive reviews of the corrosion of coatings have appeared regularly since early 1970; the purpose of this paper is not to repeat the published materials but rather to focus on research trends and to point out some research prospects. High-velocity oxy-fuel (HVOF) spraying is a new and rapidly developing technology in combating high-temperature corrosion and is now challenging the vacuum plasma spraying technique (VPS), which is very expensive (capital costs approximately 2 million US$). HVOF coatings have very low porosity, high hardness, high abrasive resistance, good wear resistance with a strong ability to resist high-temperature corrosion resistance. The purpose here is to summarize the performance of such coatings on various substrates. The effect of coatings thickness, residual stresses induced in the substrates, pre and postheat treatment of the HVOF coatings have been reviewed with the aims of summarizing their high-temperature corrosion resistance properties.

Hot corrosion of some superalloys and role of high-velocity oxy-fuel spray coatings : a review

Mechanical properties of alloys consisting of two ductile phases

A comparative study of oxidation and hot corrosion of a cast nickel base superalloy in different corrosive environments

Effect of phase morphology on fatigue crack growth (FCG) resistance has been investigated in the case of an α-β titanium alloy. Fatigue crack growth tests with on-line crack closure measurements are performed in the microstructures varying in primary α (elongated/equiaxed/Widmanstatten) and matrix β (transformed/metastable) phase morphologies. The microstructures comprising metastable β matrix are observed to yield higher FCG resistance than those for transformed β matrix, irrespective of primary α phase morphology (equiaxed or elongated). But, the effect of primary α phase morphology is dictated by the type of β phase (transformed or metastable) matrix. It is observed that in the microstructures with metastable β matrix, the equiaxed primary α as second phase possesses higher FCG resistance as compared to that of elongated α morphology. The trend is reversed if the metastable β matrix is replaced by transformed β phase. The fatigue crack path profiles are observed to be highly faceted. The detailed fractographic investigations revealed that tortuosity is introduced as a result of cleavage in α or β or in both the phases, depending upon the microstructure. The crack closure concept has been invoked to rationalize the phase morphology effects on fatigue crack growth behavior. The roughness-induced and plasticity-induced crack closure appear to be the main mechanisms governing crack growth behavior in α-β titanium alloy.

V.M. Radhakrishnan

Papers

A comparative study of oxidation and hot corrosion of a cast nickel base superalloy in different corrosive environments

Effect of phase morphology on fatigue crack growth behavior of α-β titanium alloy—A crack closure rationale

Creep crack growth behavior at 1033K of directionally solidified CM 247 LC — a cast nickel-base superalloy

Fatigue and fracture behavior of a nickel−chromium free austenitic steel

Measurement of hot corrosion of 2.25Cr1Mo steel-347H steel welded joint in K2SO4NaCl mixture