关键词： 热变形   AZ80镁合金   高温流动应力   唯象模型   Fields-Backofen模型  

摘要： 基于铸态AZ80镁合金在应变速率为0.001~1 s^(-1)、变形温度为523~673 K下的热压缩试验,分别建立了原始的和改进的Fields-Backofen (F-B)模型来描述该合金的热压缩变形行为,通过线性拟合方法确定模型中的材料参数。结果发现:原始的F-B模型仅能够描述加工硬化现象,难以准确描述合金的热变形行为;而包含软化项s的改进的F-B模型中,综合考虑了加工硬化和动态软化效应,既可以相对准确地描述加工硬化阶段的流动应力,也可以描述流动软化阶段的流动应力,其相关系数R和平均绝对相对误差AARE的计算值分别为0.9858和7.07%;然而,改进的F-B模型不能描述稳态阶段的流动应力,其预测误差可能是由于使用在所有试验条件下获得的材料参数b和s的平均值引起的。

关键词： magnesium   superplastic forming   superplasticity   electron back-scattered diffraction(EBSD)   AZ41 magnesium alloy  

摘要： An AZ41 magnesium alloy in the hot-rolled condition without further thermomechanical processing to modify its microstructure was investigated to establish its suitability for use within a superplastic forming process and to establish optimum forming *** was assessed using elevated temperature tensile testing and hot gas bulging,across a range of strain rates(1×10^(−1)−1×10^(−3)s^(−1))and temperatures(350−450℃).Circle grid analysis with GOM Aramis cameras was used to understand peak strains and material thinning in relation to industrial forming *** forming EBSD and STEM analysis was conducted to understand the mechanisms responsible for the materials formability,with dynamic recrystallization being clearly *** elongation of 520%was achieved at 450℃ and 1×10^(−3)s^(−1);industrially relevant elongation was achieved at 1×10^(−2) s^(−1) at both 450℃(195%)and 400℃(170%).

关键词： Mg−Zn−Ca−Zr alloy   extrusion−shearing process   die design   dynamic recrystallization   mechanical properties  

摘要： A novel extrusion-shearing(ES) composite process was designed to fabricate fine-grained, high strength and tough magnesium alloy. The structural parameters of an ES die were optimized by conducting an orthogonal simulation experiment using finite element software Deform-3D, and Mg-3 Zn-0.6 Ca-0.6 Zr(ZXK310) alloy was processed using the ES die. The results show that the optimized structural parameters of ES die are extrusion angle(α) of 90°, extrusion section height(h) of 15 mm and inner fillet radius(r) of 10 mm. After ES at an extrusion temperature and a die temperature of 350 °C, ZXK310 alloy exhibited good ES forming ability, and obvious dynamic recrystallization occurred in the forming area. The grain size decreased from 1.42 μm of extrusion area to 0.85 μm of the forming area. Owing to the pinning of second phase and formation of ultrafine grains, the tensile strength, yield strength and elongation of alloy reached 362 MPa, 289 MPa and 21.7%, respectively.

关键词： AZ80镁合金   显微组织   力学性能   多向锻造   EBSD分析  

摘要： 为了改善铸态AZ80镁合金组织和性能,对均匀化处理的铸态AZ80镁合金进行了多向锻造试验,并采用金相分析、EBSD (电子背散射衍射)分析和拉伸试验等方法,进行了显微组织和力学性能的测试与分析。结果表明:与锻造前相比,多向锻造后的AZ80镁合金的平均晶粒尺寸减小了约76μm、抗拉强度增加了66 MPa、屈服强度增加了79 MPa、断后伸长率增大了6%,断裂方式从脆性断裂转变为韧性断裂,多向锻造后合金内部晶粒为细小的等轴晶。因此,多向锻造显著地改善了AZ80镁合金的内部组织、提高了AZ80镁合金的力学性能。

关键词： Magnesium alloy   Strain rate   Fractograph   Hopkinson bar system   Scanning electron microscope   Material model  

摘要： The performance of a structure depends on its material characteristics under various conditions of loadings, strain rate, and temperature, and therefore, it is necessary to understand these characteristics properly for the safe and reliable design of structures. In this paper, the flow stress behavior of AZ81 magnesium alloy is determined under tensile, compressive, and flexural loads at different strain rates and temperatures. An electromechanical universal testing machine of capacity 250 kN is used to perform quasi-static tests (0.0001-0.1 s(-1)) under tension and compression;and three-point bending (flexure) tests using suitable fixtures at crosshead speeds (1-100 mm/min) for varying span lengths (80-160 mm) and orientations (flat and transverse) at room temperature, 25 degrees C. The thermal and fracture behaviors of the alloy at various temperatures (25 degrees C, 100 degrees C, 150 degrees C, and 200 degrees C) are studied under quasi-static tension (0.001 s(-1)). The heating rate of the tensile specimens is 20 degrees C/min and the soaking time is 15 min. Dynamic tensile (850-1,400 s(-1)) and compressive (1,900-3,300 s(-1)) experiments are conducted using appropriate arrangements of Hopkinson bar systems. The effects of specimen geometry on the flow stress of the alloy are observed under compression. Ductility and toughness are determined to establish the energy dissipation capacity of the alloy. Fractographs of the fractured tensile specimens are studied by scanning electron microscope (SEM). Also, the applicability of the existing Cowper-Symonds and Johnson-Cook models in the aforementioned loading conditions is discussed. (C) 2020 American Society of Civil Engineers.

关键词： 高强镁合金   挤压温度   显微组织   力学性能   Mg-8Sn-1M镁合金  

摘要： 对建筑用Mg-8Sn-1Mn高强镁合金进行了挤压试验,并进行了不同挤压温度下镁合金的显微组织和力学性能的测试与分析。结果表明:随着挤压温度的升高,Mg-8Sn-1Mn高强镁合金试样的抗拉强度和屈服强度先增大后减小,断后伸长率和平均晶粒尺寸先减小后增大。与300℃挤压相比,390℃挤压温度下试样的抗拉强度、屈服强度增大,平均晶粒尺寸减小。

关键词： AZ31B镁合金   温热渐进成形   油浴加热   成形温度   微观组织   断口形貌  

摘要： 提出一种油浴加热辅助温热渐进成形技术,利用相关装置,通过实验的方法研究了成形温度对AZ31B镁合金成形性能、微观组织及断口形貌的主要影响并分析了原因。结果表明,AZ31B镁合金板材的成形温度越高,其最大成形角度越大,当成形温度达到200℃时,发生部分再结晶,导致晶粒细化,达到250℃时已经完全再结晶,晶粒显著细化,最大成形角度达到60°。但是过高的成形温度将增加能量消耗并提高AZ31B镁合金的氧化程度,并不是最经济的选择。在当前实验条件下,250℃左右的油浴加热温度是AZ31B镁合金比较理想的成形温度,非基面滑移系基本开动并参与材料的塑性变形,使AZ31B镁合金板材的成形性能得到显著改善。

关键词： 铝、镁合金   汽车发动机   制造工艺   常见故障  

摘要： 现阶段铝、镁合金由于自身较强的性能,在汽车工业生产中有着重要应用,尤其是铝、镁合金质地较轻并且自身强度较强,在汽车零部件轻量化使用阶段具有较大的优势。本文主要介绍了铝、镁合金材料在汽车工业生产中的应用,结合东风商用汽车,简要分析了该合金在汽车发动机中的应用。通过对于常见发动机故障的分析,重视铝、镁合金在汽车工业生产中的应用。

关键词： AZ31镁合金   限制模压变形   超声喷丸   晶粒细化   硬度提高  

摘要： 以AZ31镁合金板材为实验材料,先对其进行限制模压变形,再利用超声喷丸技术进行表面处理,研究限制模压变形和超声喷丸复合工艺对材料表层组织和硬度的影响。结果表明:限制模压变形和超声喷丸具有叠加效果,该复合工艺相对于单一工艺能进一步减小AZ31镁合金的晶粒尺寸,增强表面硬度。经复合工艺处理后,AZ31镁合金的最小平均晶粒尺寸为7.52μm,相比于原始试样细化43.16%;表面硬度最高达到236 HV,相比于原始试样提高306.90%。此外,与限制模压变形相比,超声喷丸对AZ31镁合金表层组织和硬度的影响更加明显。其中,随着喷丸时间的增加,晶粒逐渐细化,硬度不断升高,但当处理时间达到400 s时,晶粒尺寸不再有明显减小,硬度达到一定极限不再变化。

关键词： WE43镁合金   热处理   显微组织   力学性能  

摘要： 采用低压铸造制备了WE43镁合金,使用OM、SEM、EDS研究了热处理前后合金的显微组织及元素分布情况,并对其力学性能进行测试,分析热处理对其力学性能的影响。结果表明,WE43镁合金铸态组织主要由α-Mg基体和晶界上的Mg_(24)Y_(5)共晶相组成。经过520℃×10h+225℃×14h热处理后,WE43镁合金主要由α-Mg基体、方块相团簇、少量残余Mg_(24)Y_(5)共晶相及针状的时效析出相组成。与铸态合金相比,热处理后WE43镁合金的抗拉强度和屈服强度显著提高,分别达到305.9 MPa和191.8 MPa,但伸长率下降至3.1%。