Effect of composition on the texture and deformation behaviour of wrought Mg alloys

The microstructure and mechanical response of three extruded magnesium alloys, Mg-3Al-1Zn (AZ31), Mg-1.5Mn (Ml) and Mg-lMn-0.4RE (ME10) are examined. The tensile yield strength of ME10 was nearly half that of AZ31 and Ml. The tensile elongations were 6%, 11% and 19% for Ml, AZ31 and ME10, respectively. This range of properties is large and is attributed to the unique extrusion texture produced in ME10, and the high density of fine particles in Ml.

The origin of "Rare Earth" texture development in extruded Mg-based alloys and its effect on tensile ductility

The extrusion behaviour, texture and tensile ductility of five binary Mg-based alloys have been examined and compared to pure Mg. The five alloying additions examined were Al, Sn, Ca, La and Gd. When these alloys are compared at equivalent grain size, the La- and Gd-containing alloys show the best ductilities. This has been attributed to a weaker extrusion texture. These two alloying additions, La and Gd, were found to also produce a new texture peak with View the MathML source parallel to the extrusion direction. This “rare earth texture” component was found to be suppressed at high extrusion temperatures. It is proposed that the View the MathML source texture component arises from oriented nucleation at shear bands.

Effect of microalloying with rare-earth elements on the texture of extruded magnesium-based alloys

A series of alloys have been produced with microalloying additions of rare-earth (RE) elements in the range of 0.1–0.4 wt.%. The alloys have been extruded to produce grain sizes of 23 ± 5 μm. The texture of the extruded alloys was measured, and it was found that the extrusion texture was weakened by the addition of RE elements. The samples with weakened extrusion textures exhibited an increase in the tensile elongation.

Re-examination of the effect of NbC precipitation on shape memory in Fe-Mn-Si-based alloys

Current literature pertaining to the shape memory effect in the Fe–Mn–Si-based system is critically discussed. It is argued that the
enhanced shape memory previously attributed to NbC precipitation is mainly due to the associated thermo-mechanical treatments.
It is concluded that the thermo-mechanical processing of the alloy is the dominant factor that determines the shape memory effect in
this alloy system.

Texture and mechanical anisotropy in three extruded magnesium alloys

One ZM61 alloy (6·2%Zn, 1·2%Mn) and two magnesium alloys containing nominally 3% of neodymium and yttrium respectively have been prepared in the form of hot extruded flat strips. Their textures and microstructures have been quantified and series of mechanical tests were carried out to determine plane stress yield loci in both the solution treated and aged conditions. The ZM61 alloy had a sharp texture and marked anisotropy of strength that could be rationalised in terms of deformation by basal <a> slip and {1012}<1011> twinning. This material was much weaker in compression than in tension. Precipitation hardening on aging caused a greater impedance to twinning than to slip with the result that the anisotropy was somewhat reduced. The Mg–3Nd alloy had a very weak and different texture but nevertheless demonstrated a pronounced anisotropy of strength. Aging increased the yield stress by about 80% and also inhibited twinning to some extent although the degree of anisotropy remained almost unaffected. The Mg–3Y alloy which showed a texture of intermediate strength was different in type from either of the others. Its strength behaviour was close to isotropic; in particular, no difference existed between tensile and compressive loading, and aging produced only a marginal increase in strength. Twins were relatively infrequent in the deformed Mg–3Y alloy but its mechanical behaviour could not be rationalised according to simple models.

Some issues relating to the ductility of wrought magnesium alloys

The present work is concerned with gaining a better understanding of the factors that control the ductility of wrought magnesium alloys. The ultimate aim is to develop alloys with vastly improved room temperature formability. It is shown that 3D tomography of fractured tensile specimens reveals disk shaped voids aligned more or less at 45 deg. to the tensile axis. These voids are consistent with twin induced void formation. It is also shown that the double twins that produce such voids form in contradiction to Schmid predictions. Finally, it is demonstrated that low levels of rare-earth additions leads to vastly improved texture and ductility in extrusions, as they do in rolled sheet.

The microstructure evolution and mechanical properties of cryorolled Al alloys

A solutionized Al2024 alloy was subjected to rolling at liquid nitrogen temperature (cryorolling) resulting in an ultra-fine stmcture. The material was also subjected to recovery annealing at 160°C. The ultrafine structured material demonstrated increased strength but very low ductility. The uniform elongation of the material after recovery annealing increased without any sacrifice of strength.

In vitro cytotoxicity of binary TI alloys for bone implants

Interest in using titanium (Ti) alloys as load-bearing implant materials has increased due to their high strength to weight ratio, lower elastic modulus, and superior biocompatibility and enhanced corrosion resistance compared to conventional metals such as stainless steel and Co-Cr alloys. In the present study, the in vitro cytotoxicity of five binary titanium alloys, Ti15Ta, Ti15Nb, Ti15Zr, Ti15Sn and Ti15Mo, was assessed using human osteosarcoma cell line, SaOS-2 cells. The Cell proliferation and viability were determined, and cell adhesion and morphology on the surfaces of the binary Ti alloys after cell culture were observed by SEM. Results indicated that the Ti binary alloys of Ti15Ta, Ti15Nb and Ti15Zr exhibited the same level of excellent biocompatibility; Ti15Sn alloy exhibited a moderate biocompatibility while Ti15Mo alloy exhibited a moderate cytotoxicity. The SaOS-2 osteoblast-like cells had flattened and spread across the surfaces of the Ti15Ta, Ti15Nb, Ti15Zr and Ti15Sn groups; however, the cell shapes on the Ti15Mo alloy was shrinking and unhealthy. These results indicated that the Mo contents should be limited to a certain level in the design and development of new Ti alloys for implant material applications.

Optimization of alloy design and hot rolling conditions for shape memory in Fe–Mn–Si-based alloys

The effect of composition and hot rolling conditions on the shape memory effect (SME) in the Fe–Mn–Si-based system has been studied to obtain improved shape memory without the need to rely on “training”. It has been found that the texture is not markedly affected by rolling conditions, and texture is therefore not a major factor in explaining variations in SME with processing conditions. Decreasing the pre-deformation temperature to below the Ms was found to have a beneficial effect on shape memory. It was found that the best SME was achieved in an alloy that had Ms just above room temperature, and had been processed by hot rolling followed by recovery annealing. Alloys of different compositions exhibited different optimum rolling temperatures for maximum shape memory performance.

Effect of second-phase particles on shape memory in Fe-Mn-Si-based alloys

The shape memory behaviour of two Fe–Mn–Si-based alloys has been investigated. One alloy was a reference alloy, and the other alloy was
similar in composition except that it contained 0.55 wt% Ti. Following solution treatment and quenching, strip samples were subjected to three types
of treatments; isothermal holding, cold rolling followed by isothermal holding, and hot rolling followed by isothermal holding. These treatments
resulted in the formation of intermetallic precipitates in the Ti-containing alloy, while the reference alloy remained precipitate-free. In comparing
the shape memory of the reference and the particle-containing alloy after identical heat treatments, it was found that the formation of precipitates
had a beneficial effect on the shape memory in all cases. In general, the larger precipitates caused a larger increase in the shape memory. The effect
of particle size on shape memory has been analysed using the current data and published results for a range of precipitate types.

Austenite stability in Fe-Mn-Si-based shape memory alloys

The stability of austenite in a number of Fe–Mn–Si-based shape memory alloys has been investigated. It was found that a grain boundary precipitate of BCC structure is formed over a wide range of alloy compositions and heat treatment temperatures. This grain boundary phase has been identified as the chi (χ) phase. Although up to 3 vol.% of the grain boundary precipitate was generated by isothermal aging in the range 500–800 °C, it was found not to markedly affect the mechanical properties or the shape memory effect. Nano-indentation indicated that the hardness and strength of the parent and precipitate phase are very similar, as are their compositions.

Processing and mechanical properties of open-cell Mg alloys

Mechanical properties of open-cellular magnesium alloys with three types of
geometric cell-structures, that is, a random round cell-structure (type A). a controlled diamond cell-structure for which the angle between the struts and the load direction is 45 degree (type B) and a controlled square cell-structure for which the angle between the struts and the loading direction is 0 degree (90 degree) (type C), are investigated by compressive tests. Results indicate that type C showed a higher collapse stress than the other two types. The collapse mechanism and the effects of the loading direction on collapse stress for the three types of magnesium alloys arc discussed from the viewpoint of bending, buckling and yielding of the struts. It is suggested that collapse for the open-cellular magnesium aHoys is associated with yielding of struts

Atom probe tomography of solute distributions in mg-based alloys

Atom probe tomography (APT) has been carried out on three magnesium-based alloys: M1 (Mg-1 wt pct Mn), AZ31(Mg-3 pct Al-1 pct Zn), and ME10 (Mg-1 pct Mn- 0.4 pct misch metal). The aims of this experiment were to measure the composition of the matrix and to investigate solute clustering in the matrix of the three different alloys. For AZ31, the matrix composition was variable but close to the bulk composition. For ME10 and M1, the matrix was depleted in alloying additions, with the remainder residing in precipitates. Most alloying additions were found to exhibit clustering to some extent, with misch metal having the strongest partitioning behavior to clusters. Solute clusters did not appear to affect mechanical twinning. It has been proposed that the clustering behavior of misch metal contributes to its ability to modify the recrystallization texture.