Magnesium Alloy Tubes Research Articles

Study on y-shape tube hydroforming of magnesium alloys at elevated temperatures

In this paper, uniaxial tensile tests are firstly conducted to evaluate the flow stress of AZ61 magnesium alloy at different temperatures and strain rates. A commercial finite element code of DEFORM 3D is used to simulate the plastic deformation of AZ61 magnesium alloy tube during a y-shape hydroforming process at elevated temperatures. The effects of loading paths with different feeding speed ratios and initial tube positions on the contact area at the counter punch surface at the bulge stage are discussed. The effects of friction coefficient on the contact area at the counter punch surface are also investigated. Finally, using a testing machine with a capacity of 40 tons of axial feeding, 30 MPa of internal pressure and 300oC of maximum temperature, y-shape hydraulic forming experiments of AZ61 magnesium alloy tubes at elevated temperatures are carried out. The analytical flow line patterns and thickness distribution of the formed product are compared with the experimental results.

Electromagnetic Field Simulation and Experiment of Electromagnetic Forming of Magnesium Alloy Tube

The AZ31 magnesium alloy tube was used for electromagnetic forming experiment of three kinds of input voltages. The stress-strain state of tube forming was analyzed. It was shown that the cause of oblique crack of tube was of axial inhomogeneous distribution and , and the cause of longitudinal crack was and of inhomogeneous distribution in circumferential direction. Moreover, the electromagnetic field and force field during electromagnetic forming was simulated by ANSYS software. The experiment proved the simulation result.

Formability testing of AZ31B magnesium alloy tube at elevated temperature

Magnesium alloy is a promising material for reaching the goal of weight reduction in automotive and aerospace industry. The mechanical properties of AZ31B seamless tube were tested by ring hoop tension test and compared with the results by axial tension test. Hydro-bulge test and newly proposed flatten-hydro-bulge test were also carried out to evaluate the formability of the tube. The effect of forming temperature and flattening displacement on the maximum expansion ratio and bursting pressure were measured and discussed. A tubular part with curved axis and different cross-sections was then manufactured successfully. It was found that the changing tendency of total elongation in hoop direction is quite different with that along axial direction. As temperature increased from RT. to 300 °C, two peaks of total elongation in hoop direction occurred at about 150 °C and 300 °C. In hydro-bulge test, the maximum expansion ratio increased as temperature increasing and reached the maximum value about 30% at 170 °C, then decreased quickly at higher temperature until 230 °C. In flatten-hydro-bulge test, flattening deformation has significant effect on the subsequent hydro-bulging process, and both maximum expansion ratio and bursting pressure decreased as flattening displacement increased. This should be taken into account during part design and process determining.

Hydraulic Bulge Tests of Magnesium Tubes at Elevated Temperatures

Evaluation of the formability of tubes is an important issue in tube hydroforming processes. Since tubular materials during tube hydroforming are under a biaxial even triaxial stress state, other biaxial-stress-based testing methods are needed. In this paper, uniaxial tensile tests at different temperatures are firstly employed to evaluate the material properties of magnesium alloy AZ61 tubes. A hydraulic bulge warm forming machine, which is used for hydraulic bulge tests with a fixed tube length, is also designed and manufactured. Using this self-designed testing machine, experiments of bulge tests of magnesium alloy AZ61 tubes at elevated temperatures are carried out. From the experimental results, the bulge formability of the magnesium alloy tubes at different temperatures is discussed.

Hydroforming of AZ61A tubular component with various cross sections

The effects of temperature on the mechanical properties and elongation of AZ61A tubular part were derived by uni-axial tension tests at various temperatures. Warm hydroforming of an AZ61A tubular part for passenger car was then numerically and experimentally investigated. The complete processes including bending, pre-forming and hydroforming were analyzed and discussed. Microstructure at the corner of the typical section was observed before and after the final hydroforming process. It is shown that the yielding strength, tensile strength and total elongation increase as temperature increases, while the elongation before necking decreases. The temperature range from 225 °C to 250 °C is more suitable for hydroforming of the AZ61A magnesium alloy tube with various cross sections. Pre-forming and hydroforming with high strain values are feasible at elevated temperature. Grain refinement is observed at the corner of the part after warm hydroforming. Thinning ratio analysis illustrates that non-uniform deformation at elevated temperature should be considered in process optimization to avoid severe local thinning.

Numerical modeling of formability of extruded magnesium alloy tubes

In this paper, a constitutive framework based on a rate-dependent crystal plasticity theory is employed to simulate the large strain deformation phenomena in hexagonal closed-packed (HCP) metals such as magnesium. The new framework is incorporated into in-house codes. Simulations are performed using the new crystal plasticity model in which crystallographic slip and deformation twinning are the principal deformation mechanisms. Simulations of various stress states (uniaxial tension, uniaxial compression and the so-called ring hoop tension test) for the magnesium alloy AM30 are performed and the results are compared with experimental observations of specimens deformed at 200 °C. Numerical simulations of forming limit diagrams (FLDs) are also performed using the Marciniak–Kuczynski (M–K) approach. With this formulation, the effects of crystallographic slip and deformation twinning on the FLD can be assessed.

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.

Finishing Advanced Surface of Magnesium Alloy Tube Based on Abrasive Belt Grinding Techology

A new maching method of pretreatment magnesium alloy surface was design based on abrasive belt grinding technology, which offered a kind of technology for magnesium alloy tube surface machining. Experimental results indicated that abrasive grain granularity, belt speed and workpiece feed speed play an important role in grinding for magnesium alloy tube surface, which made magnesium alloy tube surface roughness from 0.22 um to 2.93 um with 400 grade to 80 grade on abrasive grain granularity of belt, raise the belt speed to reduce surface roughness, but raise workpiece feed speed to deteriorate roughness.

Constitutive Description for Drawing Limit of Magnesium Alloy Tube Based on Continuum Damage Mechanics

The elasto-plastic behavior and the drawing limit of a kind of magnesium alloy tube were investigated based on the foundational theories of the larger deformation of material and continuum damage constitutive model. The corresponding finite element numerical algorithm was developed based on the constitutive model. The non-mandrel drawing limit graph according to the diameter at different tube thickness of an AZ31B tube with diameter 10mm at 250°C and drawing velocity 100mm/s was achieved, and safe & unsafe area got partitioned. The maximum damage value was evaluated to be 0.324 according to height reduction ratio limit and rigid-plastic FE analysis.

314 AZ61マグネシウム合金押出管材の超塑性成形性に及ぼす熱処理の影響(アルミニウム合金およびマグネシウム合金の創製と加工)

314 AZ61マグネシウム合金押出管材の超塑性成形性に及ぼす熱処理の影響(アルミニウム合金およびマグネシウム合金の創製と加工)

Mechanical property and formability of AZ31B extruded tube at elevated temperature

The mechanical properties of AZ31B magnesium alloy tube were tested by ring hoop tension test at different temperatures. The formability for tube hydroforming was also evaluated by free-expansion test. The results show that there exists a quick decrease of total elongation along hoop direction at the temperature range of 150–230 °C, which is quite different from that along axial direction. The total elongation along hoop direction of welded tube is quite close to that of seamless tube until 230 °C is reached. At higher temperature, the total elongation for seamless tube begins to increase while the value for welded tube continues to decrease. The maximum free expansion ratio of seamless tube increases considerably as temperature increases and reaches the maximum value of 30% at 170 °C, then decreases quickly at higher temperature.

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.

Microstructure Development in a Magnesium Alloy Tube during Ring Hoop Tension Testing and Warm Gas Forming

Microstructure Development in a Magnesium Alloy Tube during Ring Hoop Tension Testing and Warm Gas Forming

Influence of Process Parameters on T-Shape Tube HydroForming Characteristics for Magnesium Alloy

Due to the light weight and electromagnetic interference shielding capabilities in magnesium alloy material, it is widely utilized in 3C electronic components and automobile parts. However, its formability is very poor due to the phenomenon of negative strain hardening rate appearing as the deformation in large strain range, so it is usually formed as die casting or casting styles leads to much scrap, and manufacturing cost is thus increased. The objective of this study is to investigate the effect of process parameters on T-shape tube hydro-forming characteristics for magnesium alloy and it may offer the data resulting from the analysis to predict an acceptable product of tube fitting for magnesium alloy forming in industry. AZ31 magnesium alloy tube is used as the billet material for hydro-forming with hydraulic pressure as the main forming power combined with the mechanical auxiliary force from the punch to fabricate the T-shape tubing products. Finite element code DEFORM-3D is adopted to investigate the forming states of T-shape tube forming, by changing process parameters; such as punch velocity, hydraulic pressure, fillet radius of the die and tool-workpiece interface friction etc. to investigate the material flow of tube fitting, wall thickness variations, and stress and strain distributions. By qualifying the forming processes whether if it is completed or not, and synthesizing the overall analysis and judgment, we establish an admissible level of process parameter range for complete tube manufacture. The results show that suitable mechanical force can help material flow, prevent large strain deformation falling into the area of negative strain hardening rate, enhance magnesium alloy to become easy in forming and make tube fitting to be formed successfully.

Development of a New Wrought Magnesium-Aluminum-Manganese Alloy AM30

A new wrought magnesium alloy, AM30 (Mg-3 pct Al-0.4 pct Mn), has been developed. Compared to the current workhorse commercial wrought magnesium alloy AZ31 (Mg-3 pct Al-1 pct Zn), the new AM30 alloy has 20 to 50 pct higher maximum extrusion speed, up to 50 pct ductility improvement at temperatures up to 200 °C, with similar yield and tensile strengths. The tensile behavior of AM30 and AZ31 magnesium alloy tubes suggests a moderate temperature forming range of 100 °C to 175 °C in which strain hardening offsets plastic instability until fracture by cavity coalescence occurs. The AM30 alloy has slightly better formability than AZ31 at room and moderate temperatures, due to higher strain-hardening rates (dσ/de) and exponents (n). Microstructural evaluation indicates that twinning is the major deformation mechanism for these alloys at room and moderate temperatures in addition to slip mechanisms. Dynamic recrystallization (DRX) is observed at temperatures greater than ∼150 °C, which causes local instabilities to occur, leading to failure.

Mechanical Properties of Mg-8Zn-4Al-xCa Extruded Magnesium Alloy Tube at Elevated Temperature

Microstructures and tensile properties of Mg-8Zn-4Al-xCax=0.6wt.%, 1.0wt.%, 1.3wt.%, named as alloy 1#, 2# and 3# , respectively)extruded magnesium alloy tube were studied at room and elevated temperature. The results show that Ca can increase tensile strength of the alloy at 150 and 200°C significantly. At the temperature of 200°C, alloy 3# achieved optimal tensile properties, of which the ultimate tensile strength, the yield strength and the elongation were 165.8MPa, 108.7Mpa and 41.5% respectively. Compared with the properties of as cast ZAC8506 Magnesium alloy, it is shown that the tensile properties of alloy 3# are much higher than that of ZAC8506 at both room temperature and 150°C. Alloy 3# also gets better tensile performance than AZ91D extruded tube produced in the same way at the temperature of 200°C Mg2Al3 and Ca2Mg5Zn13 phases are found in the microstructure which should contribute to the higher performance of alloy 3# at elevated temperature

A Microstructure Study on an AZ31 Magnesium Alloy Tube after Hot Metal Gas Forming Process

An AZ31 magnesium alloy tube has been deformed by the hot metal gas forming (HMGF) technique. Microstructures before and after deformation have been investigated by using Electron Backscattered Diffraction (EBSD) and Electron Microscopy. Due to the inhomogeneous distribution by induction heating, there is a temperature gradient distribution along the tube axis. Accordingly, the deformation mechanism is also different. In the middle area of deformation zone where the temperature is ∼410 °C, almost no twinning has been found, whereas at the edge areas of deformation zone where the temperature is ∼200 °C, a high density of twins has been found. EBSD experiments show a weak (0001) fiber texture along the radial direction of the tube before and after deformation in the high-temperature zone. EBSD experiments on the low temperature deformation region were not successful due to the high stored energy. Schmid factor analysis on the EBSD data shows that, despite the (0001) fiber texture, there are still many grains favoring basal slip along both the axis direction and hoop direction.

Investigation of the influence of process parameters on hot extrusion of magnesium alloy tubes

During the hot extrusion of magnesium alloy, the change of process parameters will affect the mechanical properties of extruded products. In this study, Taguchi method and analysis of variance (ANOVA) are applied to analyze the influence of process parameters on the hot extrusion of magnesium alloy tubes under extrusion ratio of 21.05. The experiments are arranged by orthogonal array method in which magnesium alloys AZ31and AZ61 are used as outer arrays, the factors selected as inner arrays are the billet heating temperature, the initial extrusion speed, the container temperature and the lubricants. The extruded tubes will be carried out tensile test and flattening test, the test results are analyzed by the quality measurement of Taguchi method to find the relationship between the process parameters and mechanical properties of the products, and to acquire the optimal combination of parameters. Then based on the results obtained from the additive model, confirmatory experiments are performed. Besides, the microstructures of extruded tubes are observed to clarify the influence of process parameters on the grain size. Finally, with the same extrusion condition, the variations in tensile strength and flattening strength due to different compositions are discussed.

AZ31マグネシウム合金円管の<br>プレス曲げ加工性に及ぼす温度の影響

The bendability and deformation behavior of a magnesium alloy tube during press bending is experimentally investigated to clarify the effect of forming temperature. Bending experiments using a mandrel of wires are carried out at room temperature and at 473K. A magnesium alloy AZ31 circular tube with a 25.4mm outer diameter and a 1.5mm wall thickness is used in the experiments. The unique deformation behavior of the AZ31 tube is discussed in detail. In the bending experiments, the AZ31 tube was able to be bent with the internal mandrel at an R0/D0 of 2 and 473K. The bending limit of the AZ31 tube is considered to be enhanced, for the tube having a low average flow stress and a low r-value at room temperature, and a high average flow stress and a relatively low r-value at an elevated temperature in the compression range.

強ひずみ変形によるAZ31マグネシウム合金素形管材の結晶粒微細化とその超塑性特性評価

強ひずみ変形によるAZ31マグネシウム合金素形管材の<br>結晶粒微細化とその超塑性特性評価