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1
Content available Investigations of the Effect of Heat Treatment and Plastic Deformation Parameters on the Formability and Microstructure of AZ91 Alloy Castings
Majerski Krzysztof, Siemionek Ewa, Szucki Michał, Surdacki Piotr
Advances in Science and Technology. Research Journal
|
2024
|
Vol. 18, no 1
1--9
EN
The article discusses the influence of heat treatment and metal forming parameters on formability and the structure of the AZ91 cast magnesium alloy. The aim of the article is to determine the optimal parameters of homogenization and plastic deformation of sand castings made of the AZ91 alloy in order to improve their properties and structure. In this study, sand castings made from the AZ91 alloy were examined. In the first stage, the castings were homogenized at: 385°C, 400°C, 415°C and 430°C with argon as a shielding gas for 24 hours and then quenched. Subsequently the upsetting tests were conducted at 380 C; 400 C; 420 C; 440 C for two deformation values: ε=0.7 and ε=1.1. After upsetting, the samples were water- and air-cooled. At this stage, a visual assessment was made and samples without cracks were subjected supersaturation at 415 C for 6 h, and artificial aging at 175 C for 24 h. Vickers microhardness tests and microstructure assessment were carried out, at individual stages of testing. Based on the results obtained from the upsetting, structure and hardness tests, the most favorable homogenisation and plastic deformation conditions were determined for AZ91 alloy sand castings. The best results are achieved by homogenizing sand castings at 415 °C for 24 h. Among the tested parameters for conducting metal forming processing in the range of 380-440 °C and deformation values: ε=0.7 and ε=1.1, forging of sand-cast AZ91 magnesium alloy at 420 °C and deformation of ε=0.7 with water cooling seems to be the most favourable. The final heat treatment applied after the deformation process consists of supersaturation at 415 °C for 6 hours water quenching as artificial aging at 175 °C for 24. This combination of heat and plastic treatment parameters of castings allows for improvement of the structure and properties of sand castings made of the AZ91 alloy.
2
Content available Effects of Post-Weld Heat Treatment on the Microstructure and Mechanical Properties of the AZ91 Laser Welded Joint
Dziadoń Andrzej, Musiał E.
Archives of Metallurgy and Materials
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2022
|
Vol. 67, iss. 2
435--440
EN
Plates of AZ91 magnesium alloy were butt-welded using a CO2 laser. The non-equilibrium solidification of the laser-melted metal caused fragmentation of the weld microstructure as well as the supersaturation of a solid solution of aluminium in magnesium, which enabled the T5 ageing of the weld. The weld proved to be a mechanically stable part of the joint; all the tensile-tested specimens, both as-welded and post-weld T5 aged, fractured outside it. During the ageing of the supersaturated joint, which involved heat treating it to the T6 condition, the weld was the region where discontinuous precipitation was observed and this was the location of fracture in the tensile specimens. Thus, the strength properties of welded, supersaturated and aged AZ91 were much worse than when the non-welded material was T6 tempered.
3
Content available remote Influence of gradient structure on wear characteristics of centrifugally cast functionally graded magnesium matrix composites for automotive applications
Saleh Bassiouny, Jiang Jinghua, Fathi Reham, Xu Qiong, Li Yuhua, Ma Aibin
Archives of Civil and Mechanical Engineering
|
2021
|
Vol. 21, no. 1
196--218
EN
In the past few years, the functionally graded materials (FGMs) have proved useful in many industrial applications such as aerospace, automotive, transportation and infrastructure because of their advantages like the ability to control mechanical properties, residual stresses, wear, and corrosion behavior through a smooth gradation of the elements in a particular direction of the products. In this current work, the microstructural and wear properties of AZ91 alloy reinforced with silicon carbide particles (SiCp) produced through the centrifugal casting method were investigated. Four weight fractions of SiCp with 10 µm average size were used to fabricate functionally graded (FG) tubes in the two mold rotational speeds of 1200 and 1500 rpm. Microstructural, microhardness, and wear tests were used for characterizing the developed FG tubes. From the results obtained, the gradient distribution of SiC particles inside the AZ91 matrix alloy substantially improved hardness and wear resistance for the FG tubes comparing to unreinforced alloy. Moreover, the mold rotational speed is the main factor in controlling the distribution of particles, thus determining the gradient properties of the manufactured FG tubes. These findings suggest that FG tubes are useful for aerospace and automotive applications that require more excellent surface resistance.
4
Content available Structure and Mechanical Properties of the CO2 Laser Welded Joint of AZ91 Cast
Dziadoń A., Musiał E.
Archives of Foundry Engineering
|
2020
|
Vol. 20, iss. 3
9--14
EN
Plates of AZ91 cast magnesium alloy with a thickness of 3.5 mm were butt-welded using a laser power of 2000 W and helium as the shielding gas. The effect of the welding speed on the weld cross-sectional geometry and porosity was determined by microscopic analysis. It was found that to avoid the formation of macropores, welding should be carried out at a speed of 3.4 m/min or higher. Non-equilibrium solidification of the laser-melted metal causes fragmentation of the weld microstructure. Joints that were welded at optimal laser processing parameters were subjected to structural observations using optical and scanning microscopy and to mechanical tests. The mechanical properties were determined through Vickers hardness measurements in the joint cross-section and through tensile testing. The results indicate that the hardness in the fusion zone was about 20 HV (30%) higher than that of the base material. The weld proved to be a mechanically stable part of the joint; all the tensile-tested specimens fractured outside the fusion zone.
5
Content available remote Study of the microstructure and mechanical characteristics of AZ91–SiCp composites fabricated by stir casting
Saleh Bassiouny, Jiang Jinghua, Fathi Reham, Xu Qiong, Wang Lisha, Ma Aibin
Archives of Civil and Mechanical Engineering
|
2020
|
Vol. 20, no. 3
102--115
EN
In recent years, the composite materials have been very desirable by researchers for many engineering applications such as aviation and biomedical because of the tremendous characteristics of magnesium matrix metal composite. This current investigation aims to develop the AZ91/SiCp composites with various weight fractions (0, 2.5, 5 and 10 wt%) of silicon carbide particles via the stir casting method. The effect of SiC particles content on microstructure, mechanical and wear behaviour was investigated. The optical microscope, scanning electron microscopy and EDX analyses were utilized to detect the distribution of hard particles as well as the interface between the alloy and particles. Based on the findings, the homogeneous distribution of particles, refinement of grains in addition to good bonding between AZ91 alloy and particles have been achieved in produced composites. Therefore, the mechanical characteristics and wear performance are improved in composites compared with the unreinforced alloy. Moreover, these results suggest that for applications demanding high mechanical properties and wear resistance the AZ91/SiCp will be effective composites.
6
Content available Effect of Solution Treatment on Mechanical Properties of Cast AZ91-(Ca) Alloys
Jun Joong-Hwan
Archives of Metallurgy and Materials
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2019
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Vol. 64, iss. 1
265--269
EN
Effects of solution treatment on room temperature mechanical properties were studied in cast AZ91 (Mg-9%Al-1%Zn-0.2%Mn) and AZ91-0.5%Ca alloys. In as-cast state, the Ca addition contributed to the suppression of discontinuous β phase precipitation and the formation of Al2 Ca phase. After solution treatment, the AZ91 alloy had only a small amount of Al8 Mn5 particles, while β and Al2 Ca phases were still present in the Ca-containing alloy. In as-cast state, the AZ91-0.5%Ca alloy showed better yield strength and hardness than the AZ91 alloy. The solution treatment increased the elongation in both alloys, which eventually led to the increase in ultimate tensile strength. The solution treatment resulted in a marked decrease in yield strength and hardness in the AZ91 alloy, whereas the decrements in those values were relatively negligible in the Ca-containing alloy due to the residual phases and solution hardening effect of Ca.
7
Content available Dependence of Room Temperature Tensile Properties on Volume Fraction of Discontinuous Precipitates in Cast AZ91 Magnesium Alloy
Jun Joong-Hwan
Archives of Metallurgy and Materials
|
2019
|
Vol. 64, iss. 3
1183--1186
EN
The objective of this study was to investigate the dependence of the room temperature tensile properties on the volume fraction of discontinuous precipitates (DPs) in a cast AZ91 magnesium alloy. In order to obtain various volume fractions of DPs, the solution-treated alloy was aged at 428 K for up to 48 h. The volume fraction of DPs increased from 0% to 72% with an increase in the aging time up to 24 h; for aging times longer than 24 h, discontinuous precipitation was substantially inhibited owing to the occurrence of significant continuous precipitation within the α-(Mg) grains. YS and UTS of the alloy increased with the volume fraction of DPs, whereas the elongation showed a reverse trend. A relatively rapid change in the tensile properties with increasing volume fraction of DPs up to ~40% was noted, which would be due to the reduction of the effective α grain size in response to the formation of DPs along the grain boundaries.
8
Content available The Effect of Non-Equilibrium Solidification on the Structure and Mechanical Properties of AZ91 Alloy
Dziadoń A., Bucki T., Porzucek P.
Archives of Foundry Engineering
|
2018
|
Vol. 18, iss. 3
120--125
EN
AZ91 alloy was cast in a steel mould pre-exposed to three different temperatures: -196 ºC, 20 ºC and 650 ºC. The aim of the study was to determine the difference in the microstructure and mechanical properties between the castings formed in a cold mould and those solidifying under near-equilibrium conditions in a mould pre-heated to 650 ºC. Solidification at a low temperature led to dispersion of the structure elements as well as supersaturation of the solid solution of aluminium in magnesium. The heat treatment results indicate that the alloy solidified in the mould pre-exposed to 20 ºC can be successfully aged (heat treated to the T5 temper). It was found that the effect of the ageing process (T5 temper) was greater than the effect of the microstructure fragmentation, which was due to rapid solidification. The ageing results were assessed by comparing the microstructure and mechanical properties of AZ91 brought to the T5 condition with those obtained for the material in the T6 condition.
9
Content available Formation of Structure and Properties in Casting Processes on the Example of AZ91 Magnesium Alloy
Augustyn B., Szymanek M., Kapinos D., Boczkal S., Korczak P.
Archives of Foundry Engineering
|
2014
|
Vol. 14, iss. 2
43--48
EN
Contemporary materials engineering requires the use of materials characterised by high mechanical properties, as these precisely properties determine the choice of material for parts of machinery and equipment. Owing to these properties it is possible to reduce the weight and, consequently, the consumption of both material and energy. Trying to meet these expectations, the designers are increasingly looking for solutions in the application of magnesium alloys as materials offering a very beneficial strength-to-weight ratio. However, besides alloying elements, the properties are to a great extent shaped by the solidification conditions and related structure. The process of structure formation depends on the choice of casting method forced by the specific properties of casting or by the specific intended use of final product. The article presents a comparison of AZ91 magnesium alloys processed by different casting technologies. A short characteristic was offered for materials processed by the traditional semi-continuous casting process, which uses the solidification rates comprised in a range of 5 - 20⁰C/s, and for materials made in the process of Rapid Solidification, where the solidification rate can reach 106⁰C/s. As a result of the casting process, a feedstock in the form of billets and thin strips was obtained and was subjected next to the process of plastic forming. The article presents the results of structural analysis of the final product. The mechanical properties of the ø7 mm extruded rods were also evaluated and compared.
10
Content available remote Influence of design factors on weldability of the AZ91E alloy
Adamiec J.
Archives of Foundry Engineering
|
2010
|
Vol. 10, iss. 1 spec.
339--344
EN
Basic design factors which influence weldability include casting shape, its stiffness and type of welded joint. The influence of casting stiffness on weldability, understood as susceptibility to hot cracking, in conditions of constant joint stiffness has been determined on the basis of the Fisco test results, and in conditions of varying stiffness on the basis of the Houldcroft test.
11
Content available remote Non-standard heat treatment of cast AZ91 magnesium alloy
Braszczyńska-Malik K. N., Kamieniak J.
Archives of Foundry Engineering
|
2008
|
Vol. 8, iss. 1 spec.
31--34
EN
Results of microstructure and mechanical properties investigations of AZ91 magnesium alloy as-cast and after heat treatment are presented. Cylinder samples for uniaxially compression tests were annealed at a temperature of 423 and 623 K for 16 hours (without solution annealing). Alter annealing at 423 K precipitates of γ-Mg17Al12 phase in areas enriched in aluminum solid solution were observed whereas annealing at 623 K caused only homogenizing of solid solution. Investigated materials showed insignificant changes in ultimate compression strength and clearly increase value of yield strength of samples annealed at 623 K.
12
Vliv technologie výroby odlitku ze slitiny AZ 91 na jeho kvalitu a strukturu
Ptácková M., Klakurková L., Juřička I.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
|
2007
|
Vol. 321, z. 89
41-41
EN
The paper summarizes the results of structure analyses focused on differences in the technologies of manufacturing AZ91-alloy castings. The following technologies were used: A) die casting B) gravity casting into ceramic moulds As to their shape complexity the two castings are similar and are of roughly the same wall thickness. The die casting was selected form the manufacturing process while the precision casting made in a ceramic mould (shell mould) was cast individually within the process of verifying the potentials of manufacturing precise castings by the technology of investment casting into ceramic moulds.
13
Analysis of AZ91 alloy deformed at high velocities
Man O., Forejt M.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
|
2007
|
Vol. 321, z. 89
31-31
EN
The deformation of pure polycrystalline metals has been studied very extensively so far even in case of high strains and high deformation rates. However, only a few papers were presented about the deformation behavior of common commercial light-weight magnesium alloys under high deformation velocity (for instance [1]) but none has emphasized the effect of such extreme loading conditions on the microstructure and sub-microstructure. In this paper, there are presented some outcomes of metallographic and electronmicroscopic studies of samples of magnesium alloy AZ 91 deformed at high strain rates. The samples were made in two shape variants: one for “Split Hopkinson Pressure Bar” (SHPB) deformation test [2] and the second one for “Taylor Anvil Test” (TAT). The impact velocities were 14,36 m.s-1, 26,81 m.s-1 and 30,58 m.s-1 for SHPB test and 105,71 m.s-1 and 122,49 m.s-1 for TAT. No specimen exhibited disintegration during the test. Corresponding overall longitudinal plastic deformation of Hopkinson test specimens were 4,6%, 14,5% and 13,8% respectively. Taylor test specimens were evaluated only qualitatively. Analytical methods used were: 1. light microscopy of metallographic specimens – longitudinal sections of the test pieces; 2. scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) on the same specimens as above. Light microscopy analyses indicated growing amount of cracking at the interface of Al12Mg17 phase and the matrix with increasing impact velocity at HSPB test specimens. Results of SEM and EBSD analyses are beyond the extent of this abstract.
14
Content available remote Thermal analytical investigations of the magnesium alloy AZ91
Braszczyńska-Malik K. N.
Archives of Foundry Engineering
|
2007
|
Vol. 7, iss. 2
177-180
EN
The results of thermal derivative analysis (TDA), differential scanning calorimetric (DSC) measurements and microstructure investigations of commercial AZ91 magnesium alloy are presented. The performed examinations allowed to determine the microstructure after solidification process and also precipitation process during continuous heating of supersaturated solid solution. The [alpha]-phase and [alpha]+[gamma] semi-divorced eutectic were observed in as-cast material, whereas both discontinuous and continuous precipitates of [gamma] phase were revealed after heating supersaturated AZ91 alloy.
15
Content available remote Geometria nadtopień i współczynniki termiczne procesu nadtapiania odlewów ze stopu AZ91
Braszczyńska-Malik K. N., Mróz M.
Archiwum Odlewnictwa
|
2006
|
R. 6, nr 18/1
221--226
PL
W pracy przedstawiono wyniki badań wpływu parametrów technologicznych procesu nadtapiania metodą GTAW na geometrię nadtopień oraz sprawność cieplną i sprawność topienia odlewów ze stopu AZ91. Stosowano prędkość skanowania łukiem elektrycznym 200, 400 i 800 mm/min oraz natężenie prądu 100 200 i 300A. Określono szerokość i głębokość nadtopień. Sprawność cieplną i sprawność topienia określono z wykorzystaniem badań kalorymetrycznych. Wyznaczono związki pomiędzy geometrią nadtopień, ilością ciepła wprowadzonego do nagrzewanej próbki, sprawnością cieplną, ilością ciepła niezbędnego do utworzenia nadtopień i sprawnością topienia, a parametrami technologicznymi procesu nadtapiania.
EN
In this work the effect of GTAW process parameters on the fusion geometry, arc efficiency and melting efficient was presented. The surface fusion process was performed under varied electric arc travel speed 200, 400 and 800 mm/min and current intensity 100, 200, and 300A. Relationships between GTAW process parameters and fusion geometry, the total heat content of the weld sample, arc efficiency as well as the heat input that leads to melting of the weld volume, melting efficiency and were analyzed.
16
Intermetallic phase AL12MG17
Ptáček L., Janova D.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
|
2001
|
Vol. 279, z. 72
81-83
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