scholarly journals Structural Aspects of Remelting of the AZ91 Magnesium Alloy Surface Layer

2016 ◽  
Vol 16 (1) ◽  
pp. 13-18
Author(s):  
J. Iwaszko ◽  
M. Strzelecka

Abstract In this study, modification of the AZ91 magnesium alloy surface layer with a CO2 continuous wave operation laser has been taken on. The extent and character of structural changes generated in the surface layer of the material was being assessed on the basis of both macro- and microscopy investigations, and the EDX analysis. Considerable changes in the structure of the AZ91 alloy surface layer and the morphology of phases have been found. The remelting processing was accompanied by a strong refinement of the structure and a more uniform distribution of individual phases. The conducted investigations showed that the remelting zone dimensions are a result of the process parameters, and that they can be controlled by an appropriate combination of basic remelting parameters, i.e. the laser power, the distance from the sample surface, and the scanning rate. The investigations and the obtained results revealed the possibility of an effective modification of the AZ91 magnesium alloy surface layer in the process of remelting carried out with a CO2 laser beam.

2007 ◽  
Vol 546-549 ◽  
pp. 547-550
Author(s):  
Wei Lv ◽  
Hui Zhao ◽  
Zhong Han ◽  
Zhen Liu

Effect of pulsed high-energy electron beam on the surface modification and the state of surface layer and wear resistance of AZ91 magnesium alloy have been investigated in this study. Optical microscope (OM) and X-ray diffraction (XRD) were employed to characterize the microstructure and phase composition of the modified surface layer. It was found that the thickness of melted layer on the surface varied with electron beam current and the numbers of pulses, the treated surface layer exhibited higher hardness than AZ91 alloy. The friction coefficient and the wear volume of AZ91 alloy after electron beam treatment decrease markedly. The wear resistance of treated samples were significantly improved, which may be attributed to high hardness as a result of grain refinement.


2013 ◽  
Vol 58 (2) ◽  
pp. 619-624 ◽  
Author(s):  
M. Szafarska ◽  
J. Iwaszko ◽  
K. Kudła ◽  
I. Łegowik

The main aim of the study was the evaluation of magnesium alloy surface treatment effectiveness using high-energy heat sources, i.e. a Yb-YAG Disk Laser and the GTAW method. The AZ91 and AM60 commercial magnesium alloys were subject to surface layer modification. Because of the physicochemical properties of the materials studied in case of the GTAW method, it was necessary to provide the welding stand with additional equipment. A novel two-torch set with torches operating in tandem was developed within the experiment. The effectiveness of specimen remelting using a laser and the GTAW method was verified based on macro- and microscopic examinations as well as in X-ray phase analysis and hardness measurements. In addition, the remelting parameters were optimised. The proposed treatment methodology enabled the achieving of the intended result and effective modification of a magnesium alloy surface layer.


Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4010
Author(s):  
Grzegorz Banaszek ◽  
Teresa Bajor ◽  
Anna Kawałek ◽  
Tomasz Garstka

This paper presents the results of numerical tests of the process of forging magnesium alloy ingots (AZ91) on a hydraulic press with the use of flat and proprietary shaped anvils. The analysis of the hydrostatic pressure distribution and the deformation intensity was carried out. It is one of the elements used for determining the assumptions for the technology of forging to obtain a semi-finished product from the AZ91 alloy with good strength properties. The aim of the research was to reduce the number of forging passes, which will shorten the operation time and reduce the product manufacturing costs. Numerical tests of the AZ91 magnesium alloy were carried out using commercial Forge®NxT software.


Author(s):  
Mohd Imran Ansari ◽  
Dineshsingh G Thakur

Incorporation of fine nanoparticles and cationic surfactant (Aliquat 336) within an ENi–P matrix has given a new dimension to the field of nanocomposite coatings. It describes the surface engineering processes currently used for the protection of AZ91 magnesium alloy surface against wear, including electroless nano-composite coatings. The present work aims to investigate the influence of Aliquat 336 cationic surfactant on the microhardness and tribological properties of electroless (Ni–P–ZnO) ternary alloy nanocomposite coatings on AZ91 magnesium alloy substrate from acidic bath. The results revealed that there was a significant improvement in the microhardness and wear resistance of the coated surface by the addition of cationic surfactant at a concentration of 1.5 g/L as compared to the coating obtained without the addition of cationic surfactant in the chemical bath. These results are thus clearly indicative of the fact that the component of life of members made from substrate subjected to nanocomposite coatings with varying the concentration of surfactant can be greatly improved, thereby preventing early or regular failures, and increasing service life.


2007 ◽  
Vol 546-549 ◽  
pp. 155-158
Author(s):  
Qu Dong Wang ◽  
Yang Zhao ◽  
Qing Hua Li

Effects of CaCO3 modificator on microstructure and mechanical properties of cast AZ91 Magnesium alloy have been investigated. Tensile fracture behavior of AZ91 alloys modified by CaCO3 has also been studied. Results show that CaCO3 modificator can obviously refine the grain of AZ91 magnesium alloy and Mg17Al12. Mg17Al12 in grain boundary of AZ91 alloy after modified by CaCO3 changes from continuous reticular structure to discontinuous reticular structure, even so much as granular structure and rod structure. After modified by 0.5wt% CaCO3 modificator, ultimate tensile strength, yield strength, impact toughness and elongation of AZ91 alloy increase from 186MPa to 200MPa, from 147MPa to 160MPa, from 4J to 9J and from 2.6% to 5%, respectively. And 0.5wt% CaCO3 modificator brings about an optimal refining effect. The study also shows that the fracture mechanism of modified AZ91 alloy is between cleavage fracture and quasi-cleavage fracture, which is as same as that of unmodified AZ91 alloy.


2017 ◽  
Vol 898 ◽  
pp. 1369-1380 ◽  
Author(s):  
Hui Min Han ◽  
Dan Tong Wang ◽  
Hua Qian Yu ◽  
Min Zuo ◽  
Li Hong Wang ◽  
...  

The ceria coatings on AZ91 substrates were successfully synthesized by chemical conversion and the corrosion resistance of AZ91 samples with and without ceria coatings were evaluated by means of electrochemical corrosion in 3.5 wt.% NaCl solution. According to the parameters derived from the polarization date, the Icorr (the corrosion current density) values of the coated samples are smaller than that of bare one, indicating that the corrosion resistance of AZ91 alloys has been improved to some extent. The influence of fluoridated pretreatment, inter-layer heat treatment, sintering temperature and the layer of films on the performance of ceria coatings were also investigated. It was found that the inter-layer heat treatment has no influence on improving the anticorrosion resistance of AZ91 alloy. In comparison with the bare one, the Icorr of optimal sample is about 0.0219mA/cm2, which decreases by two orders of magnitude, indicating that the ceria coatings could significantly improve the corrosion resistance of AZ91 magnesium alloy.


Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1357 ◽  
Author(s):  
Jaromír Wasserbauer ◽  
Martin Buchtík ◽  
Jakub Tkacz ◽  
Stanislava Fintová ◽  
Jozef Minda ◽  
...  

The corrosion behavior of duplex Ni-P coatings deposited on AZ91 magnesium alloy was studied. The electroless deposition process of duplex Ni-P coating consisted in the preparation of low-phosphorus Ni-P coating (5.7 wt.% of P), which served as a bond coating and high-phosphorus Ni-P coating (11.5 wt.% of P) deposited on it. The duplex Ni-P coatings with the thickness of 25, 50, 75 and 100 µm were deposited on AZ91 magnesium alloy. The electrochemical corrosion behavior of coated AZ91 magnesium alloy was investigated by electrochemical impedance spectroscopy and potentiodynamic polarization method in 0.1 M NaCl. Obtained results showed a significant improvement in the corrosion resistance of coated specimens when compared to uncoated AZ91 magnesium alloy. From the results of the immersion tests in 3.5 wt.% NaCl, 10% solution of HCl and NaOH and 5% neutral salt spray, a noticeable increase in the corrosion resistance with the increasing thickness of the Ni-P coating was observed.


Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2331 ◽  
Author(s):  
Yang Chen ◽  
Zheng Yin ◽  
Hong Yan ◽  
Guo-Hua Zhou ◽  
Xiao-Quan Wu ◽  
...  

The effects of samarium (Sm) on the microstructure and corrosion behavior of AZ91 magnesium alloy treated by ultrasonic vibration were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and electrochemical measurements. The results showed that the addition of Sm resulted in the formation of Al2Sm, which reduced the volume fraction of the β-Mg17Al12 phase and changed its morphology to fine granular. The AZ91–Sm alloys treated by ultrasonic vibration revealed relatively lower weight loss, hydrogen evolution, and corrosion current density values compared to the ultrasonic-treated AZ91 alloy prepared without Sm. Locally, a coarse β phase in the ultrasonic-treated AZ91 alloy accelerated the possibility of micro-galvanic corrosion growing into the matrix. In the prepared AZ91–Sm alloys treated by ultrasonic vibration, the fine β and Al2Sm phases reduced the probability of micro-galvanic corrosion growth and, therefore, formed a uniform corrosion layer on the surface of the alloys.


Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 290 ◽  
Author(s):  
Alaa F. Abd El-Rehim ◽  
Heba Y. Zahran ◽  
Doaa M. Habashy ◽  
Hana M. Al-Masoud

In this study, an artificial neural network (ANN) model was used to simulate and predict the Vickers hardness of AZ91 magnesium alloy. The samples of AZ91 alloy were aged at different temperatures (Ta = 100 to 300 °C) for different durations (ta = 4 to 192 h) followed by water quenching at 25 °C. The age-hardening response of the samples was investigated by hardness measurements. The microstructure investigations showed that only discontinuous precipitates formed at low aging temperatures (100 and 150 °C), while continuous precipitates invaded all the samples at a high aging temperature (300 °C). Both discontinuous and continuous precipitates formed at the intermediate aging temperatures (200 and 250 °C). X-ray diffraction (XRD) analysis revealed that the microstructure comprised two phases: The α-Mg matrix and intermetallic β-Mg17Al12 phase. The alteration of the crystalline lattice parameters a, c, and c/a ratio with the aging time at various aging temperatures was also investigated. Both c and c/a ratio had the same behavior with aging time while a had an inverse trend. The observed variations of the lattice parameters were attributed to the mode of precipitation in AZ91 alloy. The ANN findings for the simulation and prediction perfectly conformed to the experimental data.


2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Deepak Kumar ◽  
Jayant Jain ◽  
Tulsi Bisht ◽  
Anuz Zindal

The present work involves the study of the effect of precipitates on mechanical and tribological properties of AZ91 magnesium alloy. Optical microscopy, scanning electron microscopy (SEM), and nanoindentation were used to characterize the microstructures and mechanical properties of the alloy. In addition, the wear behavior of the alloy was deduced using a pin-on disk tribological configuration under unidirectional sliding against steel (AISI 250). The elastic modulus of AZ91 alloy was found to vary significantly with changing precipitation state. The tribological evaluations showed that the specific wear-rate of solutionized sample is lowest as compared to the aged samples. This was attributed to the absence of γ-Mg17Al12 phase. Examination of worn surfaces suggested that microploughing coupled with the adhesive mode of wear is the main wear mechanism in the aged samples.


Sign in / Sign up

Export Citation Format

Share Document