Al-Mn Compounds Research Articles

Abrasive Wear Performance of Hot-Dipping Al-Mn Alloy Coatings on Q235

The Q235 steel was modified by hot-dip-aluminizing technique, and Al-Mn alloy layer was obtained on the steel surface. Scan electron microscopy (SEM), X-ray diffraction (XRD) and abrasive wear tester were used to investigate the microstructure and wear performance of the Al-Mn alloy coatings. The results show that the surface of the obtained pure aluminum coatings is acicular, while blocks Al-Mn compounds phase exists in Al-Mn alloys layer, and the Al-Mn alloy layer is composed of Al, FeAl3, Fe2Al5 and MnAl6 phases. The experimental results showed that wear weight loss of aluminum coating is more than Q235 steel. However, after manganese added to the aluminum, Al-Mn alloy coating abrasion wear loss of weight far below the Q235 steel and aluminum coating. And weight loss increases along with Mn content decreases. When worn after 100 h, Al-13% wtMn wear alloy coating weight loss of 45% of Q235 steel, aluminum coating of 35%. So the hot-dipping Al-Mn alloy layer has excellent abrasive wear resistance.

ろう付加熱後に180℃熱処理したAl–Mn–Cu系合金の粒界腐食感受性

The alternation of an air-conditioner refrigerant from a freon-based refrigerant to CO2 is proposed. A maximum temperature in the CO2 heat-exchange cycle approaches to 180°C after brazing, which might affect susceptibility to intergranular corrosion. In this work, the intergranular corrosion susceptibility of Al–Mn–Cu alloys heat treated at 180°C after brazing was investigated. In both of the heat treated and non-treated Al–Mn–Cu alloys, Al–Cu intermetallic compounds were observed at grain boundaries, while in the non-treated Al–Mn–Cu alloys, Al–Mn intermetallic compounds also existed at the grain boundaries, being in contact with the Al–Cu compounds. The observation indicates that the Al–Mn compounds promote precipitation of the Al–Cu compounds at the grain boundaries. It also means development of Cu depleted zone along the grain boundaries. However, the intergranular corrosion susceptibility was decreased when the heat-treatment time become longer because Cu solid solubility in the grains decreased down to the same level of the Cu depleted zone. With the Mn concentration, the decreasing rate is accelerated and the time needed to show no susceptibility is shortened.

Phonon and thermodynamic properties of Al–Mn compounds: A first-principles study

Based on first-principles calculations within the projector augmented wave method and the generalized gradient approximation, the structural, thermodynamic as well as phonon properties of Al–Mn compounds have been investigated. The compounds studied include Al12Mn, Al6Mn, Al8Mn5, Al10Mn3, Al11Mn4 (low temperature phase), γ-AlMn, ε-AlMn, and τ-AlMn. Besides phonon calculations, Debye model is also used to evaluate the thermodynamic properties at elevated temperatures, which are compared with available data from experiments and thermodynamic modeling. A good agreement is found between first-principles calculations and experimental values or CALPHAD-type calculations. For Al–Mn compounds with lower Mn content, it is observed that (i) the equilibrium volume decreases roughly linearly while the bulk modulus increases roughly linearly with increasing Mn content, (ii) the bonding strength follows the trend of Al–Al>Al–Mn (and Mn–Mn) at a fixed bond length, and (iii) roughly the higher the Mn content of Al–Mn compounds, the smaller the vibrational contribution to entropy, and in turn, to Gibbs energy. The demonstrated methodology herein, as well as the predicted thermodynamic properties, provides helpful insights into the stability of phases and thermodynamic modeling, especially for system where the experimental information is lacking or less reliable.

Microstructure evolution of semi-solid Mg-14Al-0.5Mn alloys during isothermal heat treatment

A new Mg-14Al-0.5Mn alloy that exhibits a wide solidification range and sufficient fluidity for semi-solid forming was designed. And the microstructure evolution of semi-solid Mg-14Al-0.5Mn alloy during isothermal heat treatment was investigated. The mechanism of the microstructure evolution and the processing conditions for isothermal heat treatment were also discussed. The results show that the microstructures of cast alloys consist of α-Mg, β-Mg 17Al 12 and a small amount of Al-Mn compounds. After holding at 520 °C for 3 min, the phases of β-Mg 17Al 12 and eutectic mixtures in the Mg-14Al-0.5Mn alloy melt and the microstructures of α-Mg change from developed dendrites to irregular solid particles. With increasing the isothermal time, the amount of liquid increases, and the solid particles grow large and become spherical. When the holding time lasts for 20 min or even longer, the solid and liquid phases achieve a state of dynamic equilibrium.

Effects of manganese addition on microstructure and press formability of hot-rolled Mg–Al–Zn alloy sheets

Differential speed rolling (DSR) has been carried out on AZ31 alloys with Mn additions of 0 to 0.6 wt% for investigating the effects of Mn on microstructure, texture, mechanical properties, and formability. The Al–Mn compounds were formed in the sample with a Mn addition of only 0.2 wt% because of its low solid-solubility limit. There were tiny differences among the DSR-processed AZ31 alloys with different Mn contents, while the AZ31 alloy without Mn addition exhibited a more homogeneous microstructure, a weaker basal texture intensity, and a much superior formability together with a larger likelihood of grain growth during annealing. The Mn dissolving in αMg matrix exerted a far stronger influence on the resulting properties compared with those existing in form of the Al–Mn compounds. The Mn solute atoms induced an increase in c/a ratio, which may suppress activity of nonbasal slips and in turn degrade the deformation capability.

Effects of Manganese and/or Carbon on the Grain Refinement of Mg-3Al Alloy

The effects of manganese and/or carbon on the grain refinement of Mg-3Al alloy have been investigated in the present study. Significant grain refinement was obtained for the Mg-3Al alloy modified with either carbon or Al-Mn master alloy. There existed an optimal content of 0:1� 0:2 mass%Mn to obtain refining grain size for the Mg-3Al alloy. The Al-Mn intermetallic particles with molar ratio of 1:1 were considered as potent nuclei for Mg grains. The addition of Mn had no obvious effect on the grain size for the Mg-3Al alloy which was refined by 0.2 mass%C. The Al-C-O-Mn compounds were considered as the potent nuclei for Mg grains. A new hypothesis that the particles of Al-Mn compounds with Al4C3 coating film can act as potent nuclei for Mg grains was proposed. (doi:10.2320/matertrans.MRA2007196) with carbon or not. The ultimate purpose is to provide the important data to develop a suitable and reliable grain refiner to be applied for Mg-Al alloys. 2. Experimental Procedures The raw materials used in the present study included relatively high purity magnesium (99.95 mass%Mg, 0.002 mass%Fe, 0.002 mass%Mn), high purity aluminum (99.99 mass%Al), carbon powder (45 mm in average diameter and purity of higher than 99 mass%), magnesium powder (200� 400 mm in size and purity of higher than 99 mass%) and aluminum powder (70� 150 mm in size and purity of higher than 99.5 mass%). The pellets (about 3 mm in diameter and 5� 10 mm in height) comprised of carbon powder, magnesium powder and aluminum powder at a mass ratio of 1:5:4 were prepared by using a cold isostatic press (CIP) under a pressure of 150 MPa for 1 h. The Al-20 mass%Mn master alloy was prepared in advance as follows. The pure aluminium and electrolytic manganese were melted together at 950 � C, and then the Al-Mn melt was poured into a copper mould at a high cooling rate. The MgO crucible having high purity of more than 99.5 mass% was used in the present study. The pure Mg and Al as well as Al-20 mass%Mn master alloy were melted together in an electric resistance furnace at the temperature of 780 � C. In the present study, the Al content in the prepared samples was controlled to be at constant 3 mass% and the Mn content was controlled to be at 0.05 mass%, 0.1 mass%, 0.2 mass%, 0.5 mass% in turn. After the pellets containing carbon were plunged into the melt, the melt was held for 10 min. Then it was manually stirred for 1 min with a magnesia rod, and

Phase Analysis of Al-Mn Compounds in the AZ Magnesium Alloys

The powders of Al-Mn phases were obtained from the as-cast, as-rolled and as-extruded AZ magnesium alloys (AZ31, AZ61) by using the extraction technology, which was found to be one of the effective methods for analyzing Al-Mn phases in the AZ magnesium alloys. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion X-ray detector (EDX) were used to investigate the structure and morphology of these compound powders. The results showed that manganese existed in both the way of Al8Mn5 phases and dissociated manganese particles in the AZ magnesium alloys, and rolling or extrusion process did not change the type of the Al8Mn5 phases. SEM observation showed that Al8Mn5 phases were formed mainly in dendrite and leaf shape with the size of 15-100μm in the as-cast AZ magnesium alloys, and were broken into fine spherical fragments with the size of about 4-5μm after rolling or extrusion.

Effects of Manganese on Microstructure and Mechanical Properties of AZ31 Magnesium Alloy Processed by Differential Speed Rolling

A DSR processing with a roll speed ratio of 1.08 was carried out on an AZ31 alloys with Mn additions of 0, 0.2, 0.4 and 0.6 wt.% for investigating the effects of Mn on the microstructural evolution and mechanical properties. The amount of the Al-Mn compounds increased with increasing the Mn content. Compare with the DSR processed sheet without Mn addition with a homogeneous grain size, those with Mn additions exhibited an inhomogeneous microstructure due to the appearance of the shear bands comprising the small grains around 5 μm. The Mn addition exhibited a significant effect in grain refinement even for a low content of 0.2 wt.%, which reduced the average grain size from about 25 μm to 10 μm. The Mn addition resulted in the significant increases in the tensile strength and the 0.2% proof stress by about 25 MPa and 40 MPa, respectively.

マグネシウム合金の単結晶ダイヤモンド工具による超精密切削加工

Magnesium and magnesium alloys are increasingly being applied for various products and the application to precise machine parts is expected. This paper deals with an experimental study of ultra-precision diamond cutting of magnesium and magnesium alloys. In order to investigate the micro cutting performance and clarify the problem in the generation of good mirror surface, the ultra-precision cutting tests of magnesium and magnesium alloys with single crystal diamond tool are carried out. The cutting force, the chip formation and the surface integrity of finished surface in the micro cutting are mainly examined and discussed. Consequently, it is observed that the specific cutting force and the ratio of thrust force to principle force significantly increase under the condition of smaller depth of cut. The mirror surface with roughness (Ry) of 100 nm or less is obtained in this experiment. However, Al–Mn compounds cause the scratches on the finished surface and deteriorate the surface integrity. The continuous type of chip is formed in micro cutting, while the saw-tooth type of chip is formed in the conventional cutting.

ＡＺ３１マグネシウム合金圧延板の引張特性に及ぼすＭｎ量の影響

Samples of Mg-3%Al-1%Zn(AZ31) alloy containing 0∼0.5 mass%Mn were prepared. They were then hot rolled and subsequently annealed. The effect of the amount of Mn content on their microstructures and deformation behavior during tensile tests was investigated. As Mn content increases, a large amount of Al-Mn compounds is crystallized in the alloys. The grain sizes of hot rolled specimens are significantly reduced but there is only a slight difference in the grain size of each alloy. After annealing for 1 h, significant grain growth occurs in 0%Mn alloy. On the other hand, the grain growth is sufficiently suppressed at 0.15%Mn content but it is hardly affected by further Mn addition. The tensile strength and 0.2% proof stress are improved by Mn addition of 0.05% or more, but those of the 0.1%∼0.5%Mn alloys are almost the same, because particles of Al-Mn compounds do not contribute to the strength of the alloys. In the annealed specimens, larger elongations are obtained in 0.15%Mn-containing alloy than in other alloys due to activation of non-basal slip and uniform elongation without deformation band.

Preferred Mn spacings in Al-Mn compounds.

A model pair potential is calculated for Mn-Mn pairs in Al using a Green's function method. The pair potential has a preferred spacing of 4.7 A. The energy resulting from these Mn-Mn interactions strongly favors the Al 6 Mn, a-AlMnSi, and icosahedral quasicrystal structures relative to competing simple structures, providing a possible mechanism for stabilizing the complex structures

Electron Channelling Enhanced Microanalysis on Ni–Al–Mn and Al–Mn–Si

Atom location by channelling enhanced microanalysis (ALCHEMI) was performed for Ni–Al–Mn compounds and Al–Mn–Si quasicrystals. For Ni75Al25−xMnx (x=5, 9) with the L12-type structure, an occupation fraction of Mn atoms at the Ni site was quantitatively determined using planar channelling conditions. The occupation fraction increases with the Mn concentration or by quenching the compound from high temperature. In quasicrystals of Al74Mn20Si6 and Al68Mn20Ru8Si4, axial channelling conditions were used to locate Si and Ru, respectively. It was shown that Si atoms occupy the Al site in Al74Mn20Si6 whereas Ru atoms occupy the site different from that of Al in Al68Mn20Ru8Si4.