Effect of pre-straining on the aging behavior and mechanical properties of an Al-Cu-Mg-Ag alloy

The effects of cold deformation prior to aging on the precipitation behavior, microstructure and mechanical properties of an Al-5.6Cu-0.72 Mg-0.5Ag-0.32Mn-0.17Sc-0.12Zr (in wt%) alloy were investigated. Pre-straining disrupts the formation of Mg–Ag co-clusters, modifying the normal precipitation sequenc

Effect of grain size on cryogenic mechanical properties of an Al-Mg-Sc alloy

An aluminum alloy with a chemical composition of Al-6%Mg-0.35%Mn-0.2%Sc- 0.08%Zr-0.07%Cr (in wt.) and an initial grain size of ~22 μm was subjected to equal-channel angular pressing (ECAP) at 593 К up to a total strain of ~12. Extensive grain refinement provided the formation of fully recrystallized structure with an average grain size of -0.6 μm. The mechanical properties of the alloy in two different structural conditions were examined at temperatures ranging from 77 to 293 K. It was shown that ECAP highly enhanced the strength, ductility and fracture toughness of the material over the wide temperature interval. Positive effect of grain refinement tends to increase with decreasing temperature due to suppression of brittle intergranular fractur

Effect of rolling on mechanical properties and fatigue behavior of an Al-Mg-Sc-Zr alloy

An aluminum alloy with a chemical composition of Al-6%Mg-0.35%Mn-0.2%Sc-0.08%Zr-0.07%Cr (in wt.) was rolled up to different reductions of 75, 88 and 95% at 360°C and at ambient temperature. The static mechanical properties and the high-cyclic fatigue (HCF) life were examined. It was shown that the hot rolling results in increased yield stress (YS) and ultimate tensile strength (UTS). However, ductility and fatigue limit of the hot rolled alloy and initial as-cast ingot are nearly the sam

Abnormal grain growth in fine-grained aluminum produced by friction-stir welding

In this work, fundamental aspects of abnormal grain growth, which typically occurs during annealing of friction-stir welded (FSW) aluminium, were studie

Strengthening mechanisms in a Zr-modified 5083 alloy deformed to high strains

The effect of extensive grain refinement through equal-channel angular processing (ECAP) at 300°C on the mechanical properties was examined in a Zr-modified 5083 aluminum alloy. It was shown that any increase in the yield stress (YS) by increasing the number of pressings was attributed to additional contributions from three strengthening mechanisms :(i) grain boundary strengthening related to the size of the crystallites bounded by deformation-induced high-angle boundaries (HAB), (ii) dislocation strengthening related to highly increased dislocation density and(iii)solute strengthening related to promoting dynamic strain aging (DSA) by intense plastic strainin

Mechanisms of dynamic recrystallization in aluminum alloys

Mechanisms of dynamic recrystallization operating at severe plastic deformation in a wide temperature range are reviewed for aluminum alloys. The main mechanism of grain refinement in all aluminum alloys is continuous dynamic recrystallization (CDRX). Temperature, deformation process and distribution of secondary phases strongly affect the CDRX mechanism. Initial formation of geometrically necessary boundaries (GNBs) and a dispersion of nanoscale particles accelerate CDRX facilitating the formation of a 3D network of low-angle boundaries (LAB) followed by their gradual transformation to high-angle boundaries (HAB

Effect of cold plastic deformation prior to ageing on creep resistance of an Al-Cu-Mg-Ag alloy

Effect of thermomechanical processing on creep resistance at 150°C of an Al-5.6Cu- 0.72Mg-0.5Ag-0.32Mn-0.17Sc-0.12Zr (wt. %) alloy was examined. It was shown that increasing strain prior to artificial aging provides achieving high strength. However, a degradation of the creep resistance, i.e., significant decrease in the rupture time and increase in the minimal creep rate, took place, concurrently. The effect of cold rolling on the strength and creep resistance is discussed in relation with the strain effect on the dispersion of secondary phase

Effect of multidirectional forging and equal channel angular pressing on ultrafine grain formation in a Cu-Cr-Zr alloy

The microstructure evolution was investigated in a Cu-0.3%Cr -0.5%Zr alloy subjected to large plastic deformation at temperature of 400° C. Two methods of large plastic deformation, i.e., equal channel ang ular pressing (ECAP) and multidirectional forging (MDF) were used. The large plastic deformations resulted in the development of new ultrafine grains. The formation of new ultrafine grains occurred as a result of continuous reaction, i.e., progressive incr ease in the misorientations of deformation subboundaries. The faster kinetics of microstructure evolution was observed during MDF as compared to ECAP. The MDF to a total strain of 4 resulted in the formation of uniform ultrafine grained structure, while ECAP to the same strain led to the heterogeneous microstructure consisting of new ultrafine grains and coarse remnants of original grains . Corresponding area fractions of ultrafine grains comprised 0.23 and 0.59 in the samples subjected to ECAP and MDF, respectivel

Short-range ordering and mechanical properties of a Ni-20%Cr alloy

The mechanical behavior of a coarse-grained (100 mm) nickel-base alloy nichrome (Ni-20%Cr) was studied in compression at temperatures ranging from 150 to 1000°C. It was shown that in the temperature interval of 300-600°C this alloy demonstrates the following features of mechanical behavior: i) positive temperature dependence of yield stress; ii) jerky flow associated with the Portevin-Le Chatelier (PLC) effect ; 3) very high value (115 MPa) of “threshold” stress at 650°C. These features of mechanical behavior can be related to short- range ordering (SRO). It was shown by differential scanning calorimetry that SRO takes place in this temperature range, causing PLC effect and positive temperature dependence of yield stress. In addition, SRO has persistency effect on yield stress and creep resistanceyesBelgorod State Universit

Static grain growth in an austenitic stainless steel subjected to intense plastic straining

The post-dynamic recrystallization of an ultrafine grained 304-type austenitic stainless steel was studied during annealing at 800 and 1000°C for 7.5 to 480 minutes. The initial ultrafine grained microstructures have been developed by continuous dynamic recrystallization during isothermal multidirectional forging to a total strain of ~4 at temperatures ranging from 500 to 800°C. The post-dynamic recrystallization involves a rapid softening at early stage of annealing followed by a sluggish decrease of hardness upon further annealing. A transient recrystallization at early annealing stage results in somewhat heterogeneous microstructures in the samples subjected to previous deformation at relatively low temperatures of 500-600°C. This structural heterogeneity disappears with increasing the annealing tim