Strength and Ductility with Dual Grain-Size and Texture Gradients in AZ31 Mg Alloy

Using surface rotation rolling (SRR) treatment with various vertical loads (120 to 280 N) while maintaining other processing parameters (rotation speed and horizontal velocity), the SRR-treated AZ31 Mg alloy sheets exhibit through-thickness gradients of both grain size and basal texture, as revealed by cross-sectional hardness tests and microstructure analysis. An optimal strength–ductility combination is achieved as the vertical load is around 200 N. The corresponding microstructure exhibits two characters: (1) The affected depth reaches the very center of the sheet and (2) the gradients approach the allowable maximum. Texture gradient is found to be the major contributor to the significant ductility enhancement.     

Application of Taguchi Method on Biaxial Stretch Forming of Friction Stir Processed Mg AZ31B Alloy

The present study describes the effect of friction stir processing parameters on formability of Mg AZ31B sheet under biaxial stretching. The formability of friction stir processed sheet was studied by limiting dome height test in biaxial strain deformation mode. The experiments were carried out as per the Taguchi parametric design concepts and an L9 orthogonal array was used to study the influence of various combinations of process parameters. Statistical optimization technique, ANOVA was used to determine the optimum levels and to find the significance of each process parameter. The results indicate that the traverse speed is the most significant factor followed by the rotational speed and the tilt angle in deciding the formability of friction stir processed magnesium alloy. In addition, mathematical model was developed to establish relationship between the different process variables with formability by regression analysis.     

AZ31镁合金的研究现状

综述了国内外对AZ31镁舍金的研究现状。讨论了主要合金元素对AZ31镁合金的组织和性能的影响,介绍了AZ31镁合金的晶粒细化、塑性成形技术的研究现状。对AZ31镁合金的发展前景进行分析。     

Effect of Neodymium on As-Cast Microstructure and Mechanical Properties of AZ31 Wrought Alloy

Nd in the form of powder or intermediate alloy was added to AZ31 wrought alloy. The as-obtained alloy was characterized and tested with respect to its microstructure and mechanical properties. The relationship between the microstructure, mechanical properties and tensile fracture mechanism were discussed, with relevant alloys as reference for comparison. Experimental results show that the same quantity of Nd was added into AZ31 in powder form or in intermediate alloy, the absorption rate of Nd reached only 10.8% for the former case and as high as 95% for the later case. Pure Nd powder was added, no new compound was detected, but it served as reductant and purified alloy melt, resulting in improving the tensile strength while Nd was added into AZ31 as Mg-Nd intermediate alloy. The compound Al2Nd and Mg12 Nd were formed in magnesium alloy, which were distributed in the matrix in the shapes of strip and particle, evidently refined the as-cast structure. The as-cast tensile strength (228MPa) of adding pure Nd powder approximated to the figure (245MPa) of adding Mg-Nd intermediate alloy. The tensile fracture mchanism of as-cast AZ31 transformed from cleavage fracture into quasi-cleavage fracture.     

Evaluating the Superplastic Flow of a Magnesium AZ31 Alloy Processed by Equal-Channel Angular Pressing

Experiments show that the magnesium AZ31 (Mg-3 pct Al-1 pct Zn) alloy exhibits excellent superplastic properties at 623 K (350 °C) after processing by equal-channel angular pressing using a die with a channel angle of 135 deg and a range of decreasing processing temperatures from 473 K to 413 K (200 °C to 140 °C). A maximum elongation to failure of ~1200 pct was achieved in this alloy at a tensile strain rate of 1.0 × 10^?4 s^?1. Microstructural inspection showed evidence for cavity formation and grain growth during tensile testing with the grain growth leading to significant strain hardening. An examination of the experimental data shows that grain boundary sliding is dominant during superplastic flow. Furthermore, a comprehensive review of the present results and extensive published data for the AZ31 alloy shows the exponent of the inverse grain size is given by p ≈ 2 which is consistent with grain boundary sliding as the rate-controlling flow mechanism.     

Grain Refinement Mechanisms in Gradient Nanostructured AZ31B Mg Alloy Prepared via Rotary Swaging

Metallurgical and Materials Transactions A - Gradient nanostructured AZ31B Mg alloy rods were prepared via cold rotary swaging in this study. The swaged sample exhibited the best...     

AZ31变形镁合金及其挤压工艺的研究现状

本文根据文献资料总结了AZ31变形镁合金的性能特点、高温流变应力方程及其挤压工艺的研究和应用现状，为进一步开展AZ31镁合金挤压工艺的研究，特别是计算机模拟提供了参考依据。     

均匀化热处理对AZ151镁合金显微组织的影响

采用热分析仪、光学显微镜和布氏硬度机等仪器,研究了不同的均匀化热处理条件下AZ151镁合金的显微组织和布氏硬度值,分析了温度对均匀化效果的影响以及硬度值随温度的变化,研究表明:温度是均匀化过程中的主要影响因素,并且扩散过程的速度随着温度的提高而增加;升高温度也不能使AZ151中的Mg17Al12完伞分解,AZ151镁合金合理的均匀化工艺为430℃/16 h.     

Effect of Oxide Bifilms on the Fracture Behavior of AM60B Mg Alloy

Transactions of the Indian Institute of Metals - The effect of entrained Mg oxide bifilms on the tensile properties and fracture behavior of AM60B Mg alloy was studied. For this purpose, tensile...     

AZ31变形镁合金性能与组织的研究

对商业化的AZ31B和AZ31D变形镁合金挤压后的型材进行取样,对其拉伸性能、断口形貌和金相组织进行了观察。结果表明：挤压后的镁合金发生了动态再结晶,生成了细小的等轴晶粒,从而提高了材料的强度和塑性加工性能,其中AZ31D镁合金的塑性提高得更大。在此基础上进一步对镁合金的变形机制进行探讨。     

镁合金微弧氧化研究

本文介绍以硅酸盐溶液为氧化液对AZ31镁合金进行的微弧氧化实验。讨论了氧化膜的性能，并采用正交试验的方法分析了主要成膜物质对膜性能的影响。     

Size Effects on the Mechanical Responses and Deformation Mechanisms of AZ31 Mg Foils

An integrated experimental and microstructure-based simulation research was carried out to study the effect of thickness and grain size on the mechanical response and deformation mechanism of AZ31 Mg foils. Equal channel angle pressing (ECAP) and subsequent annealing were applied to fabricate the billets with tailored microstructures. Ex situ micro-tensile tests of the foils were conducted to explore the meso-scale size effect. The experimental results show that the flow stress, ductility, and microstructure evolution of the foils are significantly affected by both grain size and thickness. With the increase of grain number (λ) in thickness, the flow stress curve changes from convex-up to a typical sigmoidal shape, and the extension twinning is remarkably suppressed. Full-field crystal plasticity simulations successfully captured the micromechanical interaction between dislocation slip and twinning. Specifically, the decrease of λ enhances the dominance of extension twinning on the mechanical response and ductility of the foils and further intensifies the interaction of deformation twinning on slip resistance. As a measurement for describing the combined effect of grain size and geometrical size, λ is a critical factor affecting the interaction and competition between dislocation slip and deformation twinning.

     

Tensile behavior of friction-stir-welded AZ31-H24 Mg alloy

In the present study, tensile behavior of friction-stir-welded AZ31 (Mg-3.6Al-1Zn-0.6Mn in wt pct)-H24 Mg alloy was investigated. It was found that the tensile property, particularly tensile elongation, of AZ31-H24 alloy was significantly degraded with friction stir welding (FSW). The tensile fracture always occurred at the boundary between the thermomechanically affected zone (TMAZ) and the stir zone (SZ) on the advancing side. The fractographic examination on the tensile-fractured AZ31-H24 alloy specimen showed a mixed mode of cleavage and dimpled rupture. The AES analysis suggested that the significant reduction in tensile elongation of friction-stir-welded AZ31-H24 Mg alloy was attributable to the entrapped oxides along the boundary between the TMAZ and SZ.     

基于数值模拟的AZ31镁合金连续流变成形浇注温度的影响

本文首先通过ANSYS数值模拟软件模拟了不同浇注温度时设备型腔内AZ31镁合金温度的变化,并确定了半固态区在型腔中的位置。然后采用连续流变成形实验设备,在不同浇注温度下进行实验,得到了部分产品。对比实验得到的产品表面质量,确定了最佳的浇注温度范围为730-750℃。同时分析了740℃浇注时型腔中合金的组织演化过程,认为合金浇注进型腔后,在工作辊的剪切搅拌作用下经历了枝晶-玫瑰晶-球状晶的演化过程。     

Taguchi Optimisation of Friction Stir Processing Parameters to Achieve Maximum Tensile Strength of Mg AZ31B Alloy

In this investigation, the effect of friction stir processing process variables such as rotational speed, traverse speed and tool tilt angle on the tensile strength of magnesium alloy AZ31B was studied. The experiments were carried out according to the Taguchi parametric design L9 at various combinations of process parameters and statistical optimization technique ANOVA was used to determine the optimum levels and to find the percentage of contribution of the process parameters. The results indicate that the rotational speed is the most significant factor followed by the traverse speed and tool tilt angle for maximising the tensile strength of the friction stir processed magnesium alloy.     

温变形对AZ31镁合金组织的影响

对铸态AZ31 镁合金在210℃温变形时的组织演变和力学性能进行分析,为进一步开发镁合金的成形工艺提供实验依据.     

AZ31镁合金在海洋大气环境中的腐蚀行为

通过室外大气暴露试验,研究了AZ31镁合金在万宁和青岛2个海洋大气环境试验站点1～5年的腐蚀规律,用失重法测定了腐蚀速率,并用SEM和XRD分析了5年后表面腐蚀形貌和腐蚀产物的组成。研究表明,AZ31镁合金暴露在海洋大气环境5年后的腐蚀动力学符合幂函数规律,万宁站的腐蚀速率高于青岛站,且腐蚀速率都随暴露时间的延长而降低,但青岛站腐蚀速率降低幅度更大,腐蚀产物膜对基体保护作用较万宁站强;AZ31镁合金暴露在万宁站和青岛站5年后的腐蚀速率分别为37.6和13.5μm·a-1,腐蚀产物以MgCl2,MgCO3,MgSO3,MgSO4,Mg5(CO3)4(OH)2·8H2O和Mg2(OH)3Cl·4H2O为主;AZ31镁合金在海洋大气环境中不耐腐蚀,表面布满点蚀坑,相对湿度对镁合金较长周期的腐蚀有显著影响。