Papers by Keyword: AZ31 Alloy

Abstract: A new type of AZ31-1.3Ca-1.0Sm-0.3La alloy was obtained in this study by adding Ca, Sm and La to AZ31 alloy. Detailed analysis results on second phases showed that Al₂Ca phases, Al₂Sm phases with two kinds of morphologies formed in as-cast AZ31-1.3Ca-1.0Sm-0.3La alloy besides Mg₁₇Al₁₂ phases, and La atoms mainly dissolved in Al₂Ca/Sm phases. The average grain size of as-cast AZ31-1.3Ca-1.0Sm-0.3La alloys was 212 μm and the grain sizes distributions were uniform. After the hot extrusion, the average grain size decreased to 5.4 μm and the grain sizes distributions were uneven. The base texture of as-extruded AZ31-1.3Ca-1.0Sm-0.3La alloy was strong, and the maximum density value was 3.25. The yield strength, ultimate tensile strength and elongation of as-extruded AZ31-1.3Ca-1.0Sm-0.3La alloy was 216 MPa, 280 MPa and 16% at RT, and 145 MPa, 188 MPa and 42% at 150°C, respectively, which are much higher than those of the common MB2 alloy both at the room temperature and 150 °C.

Abstract: In this work, the tensile properties of AZ31 Mg alloy deformed by multi-directional forging (MDF) were investigated at room temperature. And the enhanced mechanical properties of yield strength of 93 MPa, ultimate tensile strength (UTS) of 253 MPa and elongation of 29% were achieved. It is discovered that the MDF deformation makes the crystallographic orientation of original as-cast microstructure randomization, providing the condition for the following twinning during tensile deformation. In addition, the original fine grains and continuously refined grains can enhance the strength by restricting the growth of grains and motion of dislocations.

Abstract: The effect of carbon addition on the hot rolling behavior of as-cast AZ31 alloy was investigated. It is found that the carbon addition can refine the as cast grain size of the AZ31 alloy to 140μm. The edge cracking occurrence on the surface during hot-rolling of the AZ31 alloy was practically eliminated by the grain refinement. Based on the microstructure examination during the hot rolling, the improvement in rollability of the carbon added AZ31 alloy is attributed to the more homogeneous DRX process during hot rolling, which can distribute and effectively absorb strain energy and prohibit crack growth.

Abstract: Semisolid metal forming (SSF) has been regarded as a potential process to shape the wrough Mg alloy base on the thixotropy and low deformation resistance of non-dendritic semisolid slurry. Therefore, it is necessary to develop the slurry production method of wrought Mg alloy as most current researches are focused on the cast alloy. In this paper, the AZ31 billet was refined by the self-inoculation method, and the partialy remelt method was employed to produce the non-dendritic microstructure. Results indicate that both the morphology and size of the primary Mg phase in AZ31 were refined by the grain refining treatment. When the billet were reheated under 595°C and 610°C with different holding times, the morphology of primary Mg phase undergo an evolution pattern from rosette or tiny dendritic to spherical, and with the prolonged holding time, the size of primary Mg phase increased and the shape turn to irregular. Moreover, the result show that the high holding temperature shorten the evolution time from irregular to spherical and the deteriorative grains obtained earlier compared to the low holding temperature.

Abstract: The grain refining technology of AZ31 alloy by using self-inoculation method (SIM) has been developed. Results indicated that SIM significantly decreased the grain size of as-cast AZ31 billet from 287 to 58 μm, changed the morphologies and size of the β-Mg17Al12 phase and decreased the solute elements segregation along grain boundaries. The average grain size is sensitive to the diameter of a cast rod; the microstructures of the large diameter rod are relatively inhomogeneous. The grain refinement was mainly attributed to the grain multiplication which derives from heterogeneous nucleation induced by self-inoculants and free crystals and dendrite fragments enhanced by fluid director, combined with a high solidification rate of alloy melt in the metal mold.

Abstract: In order to improve plastic property of AZ31 alloy tubes at room temperature and expand application of cold rolling process in magnesium (Mg) alloys, solution treatment (T4) and cryogenic treatment of AZ31 tubes obtained by drawing were investigated in this work. The results indicate that T4 can improve the microstructure of the alloy, refine grains and eliminate twins. The optimized T4 parameter is 300 °C for 8 h, in which the average grain size of 12 μm can be obtained and elongation reaches to Max of 16.1% and tensile strength reaches to 242 MPa. Moreover, tensile strength was decreased to 211 MPa, while, elongation was improved to 25.4% by T4+cryogenic treatment at-196 °C.

Abstract: The warm tension-rotation bending process of AZ31 Mg alloy profile was simulated. The distribution of stress and equivalent plastic strain of the profile during the bending process were analyzed. The results indicate that tangential stress of cross-section of profile from the inside to outside after bending is shown as "tensile-compression-tensile-compression", which is appeared as "N"-shaped. Equivalent plastic strain of the outside of profile is maximum, which is 0.132; the inside of profile is lower, which is 0.069; the middle of profile is minimum, which is 0.003.

Abstract: Warm-rolled AZ31 alloy sheets were annealed at different temperatures ranging from 150 to 450°C. Effects of annealing temperature on microstructure and properties of warm-rolled AZ31 alloy sheets, especially the formability, were investigated. The results revealed that the Lankford value (r-value) and strain-hardening exponent (n-value) first increased and then became relatively steady with the increase of annealing temperature. The Erichsen value (IE) first increased and then decreased with the increase of annealing temperature and the AZ31 alloy sheets exhibited the highest IE of 3.02 mm when annealing at 250°C, which can be mainly attributed to a larger elongation, a lower r-value and a higher n-value.

Abstract: Hot compression test for AZ3l magnesium alloy at deformation temperatures of 523-723K and strain rates of 0.01-10s-1 were carried out using Gleeble-3500 thermo-mechanical simulator. The experimental results show that the flow stress and microstructure vary apparently with deformation process parameters. Microstructure observations show that dynamic recrystallisation (DRX) takes place during the deformation. The characteristic with the dynamic recrystallization change with the process parameters.

Abstract: Compression properties, microstructure evolution and deformation behaviors of cast and extruded AZ31 alloys are investigated. The results show that compressive yield stress, ultimate strength and ultimate compression ratio between extruded and cast AZ31 alloy are quite different. The yielding pattern of as-cast AZ31 alloy is continuous, and the yield pattern of extruded AZ31 alloy demonstrate an obvious yielding plateau mode. The angle between the fractures and specimens axis of as-cast and extruded AZ31 alloy is about 45°. A mass of reliefs and damage can be found on the specimen surface of as-cast AZ31 alloy and the twinning is main deformation sign in as-cast AZ31 alloy as seen a rough surface. The slip activity might be a predominant deformation mechanism in extruded AZ31 alloy judged by smooth surface after fracture.