A two-step processing route for achieving a superplastic forming capability in dilute magnesium alloys

Horita, Zenji; Matsubara, Kiyoshi; Makii, Koichi; Langdon, Terence G.

doi:10.1016/s1359-6462(02)00135-5

Cited by 141 publications

(62 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…46) The grain sizes of these two materials remained large even after processing by ECAP and this led subsequently to the introduction of a two-step procedure, termed EX-ECAP, in which the grain size was initially reduced by extrusion prior to conducting ECAP processing. 47,48) Unlike f.c.c. metals, the mechanism of grain refinement in magnesium alloys is not always homogeneous throughout the grains and it does not exhibit evidence of an alignment of the refined grains parallel to the shear plane.…”

Section: The Principles Of Grain Refinement In Spd Processingmentioning

confidence: 99%

Using Severe Plastic Deformation for the Processing of Advanced Engineering Materials

Figueiredo

Langdon

2009

Mater. Trans.

Self Cite

View full text Add to dashboard Cite

The processing of metals through the application of severe plastic deformation leads to significant grain refinement and provides an opportunity for achieving superior properties. The two procedures of equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) are examined with emphasis on the mechanical properties at low and high temperatures and the nature of the grain refinement. It is demonstrated that grain refinement occurs relatively homogeneously in f.c.c metals through the formation of dislocation cells or subgrains and the evolution of these cells into an array of ultrafine grains separated by high angle boundaries. By contrast, grain refinement in h.c.p. metals such as magnesium is inhomogeneous and occurs through the nucleation of new grains along the initial grain boundaries due to the high stresses generated to activate multiple slip systems. Ultrafine-grained metals generally exhibit high strength but they may exhibit weakening if the processing conditions adversely affect the precipitate morphology. If the ultrafine grains are stable at high temperatures there is a possibility of achieving excellent superplastic properties.

show abstract

Section: The Principles Of Grain Refinement In Spd Processingmentioning

confidence: 99%

Using Severe Plastic Deformation for the Processing of Advanced Engineering Materials

Figueiredo

Langdon

2009

Mater. Trans.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Earlier experiments on pure magnesium and Mg alloys showed that it is often difficult to satisfactorily process these materials in ECAP when they are used in an as-cast form 17) but excellent processing may be achieved when the alloys are extruded prior to ECAP in a process designated EX-ECAP. 18,19) In the present investigation, the alloy was received as an extruded rod with a diameter of 15 mm and it was then machined to a diameter of 10 mm. Figure 1 shows the microstructure of the as-extruded AZ61 alloy and it is apparent that the grains are reasonably equiaxed, uniformly distributed and there was an average initial grain size of $22 mm.…”

Section: Experimental Materials and Proceduresmentioning

confidence: 99%

Microstructural and Mechanical Characteristics of AZ61 Magnesium Alloy Processed by High-Pressure Torsion

et al. 2008

Self Cite

View full text Add to dashboard Cite

Experiments were conducted on an AZ61 magnesium alloy to evaluate the microstructural characteristics and the mechanical properties after processing by High-Pressure Torsion (HPT). The results show that processing by HPT produces excellent grain refinement with average grain sizes of $0:22 and $0:11 mm after processing at 423 K and room temperature, respectively. Tensile testing after HPT revealed the potential for achieving superplastic elongations with a maximum recorded elongation of 620% when testing at a temperature of 473 K. Using microhardness measurements, it is demonstrated that the the microstructure gradually evolves with increasing torsional straining in HPT so that ultimately there is a reasonably homogeneous structure across the disk.

show abstract

“…Experiments suggest that ECAP is most eective in magnesium-based alloys when used after extrusion. This two-step process consisting of hot extrusion followed by several ECAP passes is designated EX-ECAP and was used eectively with a MgZr alloy [2] and subsequently with MgAl [3] and MgAl Zn [4] alloys. The magnesium alloy AZ31, investigated in this study, is one of the most commonly used magnesium alloy in the industry [5].…”

Section: Introductionmentioning

confidence: 99%

Activation Energy for Grain Growth of the Isochronally Annealed Ultrafine Grained Magnesium Alloy after Hot Extrusion and Equal-Channel Angular Pressing (EX-ECAP)

2015

View full text Add to dashboard Cite

Magnesium alloy AZ31 prepared by hot extrusion and 4 passes of equal-channel angular pressing (EX-ECAP) has ultra-ne grained microstructure with an average grain size of 900 nm. Grain growth is analysed using a general equation for the grain growth and an Arrhenius equation. The calculated value of the activation energy for grain growth diers with the annealing temperature. The tted value of activation energy for grain growth in the intermediate temperature range (210400 • C) is in accordance with the results of other authors, but it is shown in this study that such value is abnormally low and physically meaningless. More real values of apparent activation energy in this temperature range were calculated from the model assuming a linear increase of activation energy with increasing annealing temperature. Result of this linear model of evolution of activation energy in the temperature range between 210400• C is expressed by the interval estimation of apparent activation energy values. It is concluded that the evolution of apparent activation energy can be explained by a change in the mechanism underlying the grain boundary migration. In the low temperature range, the grain boundary diusion is dominant since the material is ultra-ne grained, whereas at higher temperatures, the lattice self-diusion is more important.

show abstract

A two-step processing route for achieving a superplastic forming capability in dilute magnesium alloys

Cited by 141 publications

References 19 publications

Using Severe Plastic Deformation for the Processing of Advanced Engineering Materials

Using Severe Plastic Deformation for the Processing of Advanced Engineering Materials

Microstructural and Mechanical Characteristics of AZ61 Magnesium Alloy Processed by High-Pressure Torsion

Activation Energy for Grain Growth of the Isochronally Annealed Ultrafine Grained Magnesium Alloy after Hot Extrusion and Equal-Channel Angular Pressing (EX-ECAP)

Contact Info

Product

Resources

About