Low temperature formability of differently processed AZ31B magnesium alloy sheets

The research found changes in the performance (formability) of magnesium alloy sheets with a history of different processes. A key outcome found that the steel sheet metal processing of rolling and heat treatment caused a detrimental effect. The material's internal deformation was found to be linked to the poor formability.

Behavior of magnesium in Hank's solution aimed to trabecular pattern of natural bone

An ideal artificial bone is expected to grow together with other natural bones with aid of osteoblast cells and to fade out into other natural bones at the same rate of restructuring natural bone. Magnesium is thought to be one of candidate materials, since it has a potential to enhance natural bone growth and to homogenize the implanted artificial bodies with natural bone. In the present study, we are concerned with the formation of trabecular pattern in the natural bone to consider how to reconstruct this pattan in the artificial bone made from magnesium. For that purpose, a series of experiments were perfonned to observe the chemical behavior of dipped magnesium plate and cellular magnesium in Hank's solution. A magnesium specimen is annealed at 773 - 803 K for various periods in an atmosphere to homogenize its microstructure. Mass change of magnesium is estimated by immersing it in Hank's solution. It is well known that magnesium is easily corroded by chlorine ion. Both x-ray diffraction and energy dispersed x-ray analyses were carried out in order to identify a reaction product and its chemical composition. Mass of a magnesium specimen, which was annealed at 803 K for 32.4 ks or 14.4 ks, increases after immersing it into Hank's solution for 4.5 18 Ms (1255 h). Furthermore, the cellular magnesium, which was annealed at 803 K for 1.8 ks, fanned a reacted layer with around 80 μ in thickness and it contained Mg, Ca, P, and a little bit of CI.

Deformation modes and anisotropy in magnesium alloy AZ31

A strongly textured sheet of magnesium alloy AZ31 has been subjected to tensile testing at temperatures between ambient and 300°C. Structures have been examined by optical and transmission electron microscopy and also by atomic force microscopy to quantify surface displacements seen at grain boundaries. Plastic anisotropy varies strongly with test temperature as was observed previously by Agnew and Duygulu. The present findings do not support the view that crystallographic <c + a> becomes a major contributor to deformation at higher temperatures. Rather, the material behaviour reflects an increasing contribution from grain boundary sliding despite the relatively high strain rate (I 0^-3 s^-1) used in the mechanical tests.

Effect of particles on the formation of deformation twins in a magnesium-based alloy

The deformation behaviour of the age hardenable alloy Mg–5%Zn after different precipitation treatments has been examined. It has been found that during compressive deformation, fine particles increase the number of twins that form, but reduce the size and total volume fraction of twins. Visco-plastic selfconsistent modelling has been used to show that the presence of precipitates hardens the twin and prismatic slip systems more than the basal slip system. It is proposed that because the {10 ¯12} twin requires basal slip to accommodate the twinning shear, this twin type will always be hardened equal to, or more than, the basal slip system in response to precipitation.

Performance of wrought aluminium and magnesium alloy tubes in three-point bending

This present work examines the load carrying capacity, energy absorption and fracture characteristics of wrought magnesium and aluminium alloy tubes in three-point bending. Magnesium alloy AZ31, and aluminium alloys 6063 and 7075, were extruded into cylindrical tubes of both equivalent thickness and mass. A strong thickness effect was present meaning that the AZ31 tube had significantly higher load and energy absorption performance than an equivalent mass 6063 tube, albeit not as high as the 7075 tube. Hinge formation and maximum load was delayed for the magnesium alloy, meaning that a high energy absorption rate persisted to higher deformation displacements than the aluminium alloys. It was also found that fracture during deformation was dependent on the indenter diameter, tube thickness and lower support separation.

Role of grain boundary sliding in the anisotropy of magnesium alloys

The plastic anisotropy of magnesium alloy sheet drops rapidly with test temperature. It has previously been suggested that this may be due to an increase in the activity of (c+a) dislocations. The present note points out that the phenomenon may result, instead, from the action of grain boundary sliding. This can explain the strong effect of grain size on anisotropy. Furthermore, it points to a new avenue for alloy development.

The Challenge of inhomogeneous deformation in magnesium and its alloys

It is shown that wrought magnesium alloys display a number of significant types of deformation inhomogeneities. These are influenced by the variation in the ease of basal slip amongst grains, micro-textures, shear banding, twinning and grain boundary sliding. Key features of each of these effects are examined and their engineering consequences and challenges are identified.

The post-deformation recrystallization behaviour of magnesium alloy Mg–3Al–1Zn

Interrupted hot compression tests are employed to examine the kinetics of recrystallization in magnesium alloy Mg–3Al–1Zn. It is found that recrystallization results in an increase in the flow stress encountered in subsequent deformation. The increase in flow stress is used to infer the fraction of recrystallization and empirical equations are developed to describe the kinetics.

Effect of grain size on the performance of extruded magnesium alloy tubes in three-point bending

The performance of extruded AZ31, AZ61 and AM-EX1 tubes was examined in three-point bending. Different extrusion temperatures were used to investigate the effect of grain size on the load-carrying capacity, energy absorption and fracture propensity of the tubes. Results showed that while the peak load increased with a smaller average recrystallised grain size, the retention of large elongated un-recrystallised grains in the microstructure reduced the load. The presence of the large elongated grains also appeared detrimental to the ability of the tube to deform before fracture.

Wrought magnesium alloy

A magnesium-based alloy consisting of, by weight: 0.5 to 1.5% manganese, 0.05 to 0.5% rare earth of which more than 70% is lanthanum, 0 to 1.5% zinc and 0 to 0.1% strontium, the balance being magnesium except for incidental impurities.

New insights into the fundamental chemical nature of ionic liquid film formation on magnesium alloy surfaces

Ionic liquids (ILs) based on trihexyltetradecylphosphonium coupled with either diphenylphosphate or bis(trifluoromethanesulfonyl)amide have been shown to react with magnesium alloy surfaces, leading to the formation a surface film that can improve the corrosion resistance of the alloy. The morphology and microstructure of the magnesium surface seems critical in determining the nature of the interphase, with grain boundary phases and intermetallics within the grain, rich in zirconium and zinc, showing almost no interaction with the IL and thereby resulting in a heterogeneous surface film. This has been explained, on the basis of solid-state NMR evidence, as being due to the extremely low reactivity of the native oxide films on the intermetallics (ZrO₂ and ZnO) with the IL as compared with the magnesium-rich matrix where a magnesium hydroxide and/or carbonate inorganic surface is likely. Solid-state NMR characterization of the ZE41 alloy surface treated with the IL based on (Tf)₂N− indicates that this anion reacts to form a metal fluoride rich surface in addition to an organic component. The diphenylphosphate anion also seems to undergo an additional chemical process on the metal surface, indicating that film formation on the metal is not a simple chemical interaction between the components of the IL and the substrate but may involve electrochemical processes.

An investigation of a phosphinate-based ionic liquid for corrosion protection of magnesium alloy AZ31

This work reports a preliminary exploration of the potential of the ionic liquid trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (P_6,6,6,14M₃PPh) for use as a conversion coating agent for corrosion protection of magnesium alloy AZ31. Results obtained for the as received IL did not indicate any measureable improvement in protection. However, when the IL was allowed to reach equilibrium/saturation with moisture from the atmosphere, treatment with this ‘wet’ solution resulted in a substantial improvement in corrosion resistance. Preliminary electrochemical, optical, and spectroscopic characterization of the film will be presented along with a possible mechanism for film formation.

Corrosion of magnesium alloy ZE41 – The role of microstructural features

Magnesium alloy ZE41, used extensively in the aerospace industry, possesses excellent mechanical properties albeit poor corrosion resistance. This paper investigates the mechanism of corrosion and the interaction between the grain boundary intermetallic phases, the Zr-rich regions within the grains and the bulk Mg-rich matrix. The results of optical and scanning electron microscopy (SEM) together with energy-dispersive X-ray (EDX) and atomic force microscopy (AFM) potential map measurements have shown the importance of the microstructure in the initiation and propagation of corrosion in an aqueous environment, indicating that the Zr-rich regions play a distinct role in the early stages of corrosion in this alloy.

Synthesis and physical property characterisation of phosphonium ionic liquids based on P(O)2(OR)2− and P(O)2(R)2− anions with potential application for corrosion mitigation of magnesium alloys

Phosphonium cation based ionic liquids (ILs) have become of interest due to their unique chemical and electrochemical stability as well as their promising tribological properties. At the same time, interest has also grown in the use of phosphate and phosphinate based ionic liquids for corrosion protection of reactive metals. In this work we describe the synthesis and characterization of six novel ionic liquids based on the tetraalkylphosponium cation coupled with organophosphate and organophosphinate anions and their sulfur analogues. The conductivity and viscosity of these ILs has been measured and discussed in terms of the nature of the interactions, effect of anion basicity and the extent of ionic character. The reaction of the IL with a ZE41 magnesium aerospace alloy surface is also demonstrated.