Zesheng JI
,
Maoliang HU
,
Xiaoping ZHENG
材料科学技术（英文）
To investigate the thixotropic fluidities, microstructures and mechanical properties of semi-solid AZ91D magnesium alloy during reheating, a self-made die set with channels of different sizes were used. The results show that critical forming forces and maximal forming forces could be obtained and related to the holding times in the semi-solid forming process. In the holding time of 0-2700 s, with increasing the holding time, maximal forming force decreased sharply and critical forming force decreased slowly. In the whole thixotropic flowing process, the filling-in was steady and the surface fineness was good. The forming force increased when the slurry changed the flowing direction or flowed from the big-diameter chamber to the small-diameter one. The tensile strength and elongation to failure of the sample after holding time for 2700 s, compared to as-cast sample, are increased by approximately 42.7% and 180%, respectively, and the fractured surfaces presented dimple-like pattern.
关键词:
AZ91D magnesium alloy
,
magnesium
,
alloy
,
semi-solid
,
thixot
W.M. Mao
,
Z.S. Zhen
,
H.T. Chen
,
X.Y. Zhong
金属学报(英文版)
With the help of an electromagnetic stirring device and alloy melt quenching technology, the microstructure of semi-solid AZ91D magnesium alloy slurry stirred by a rotationally electromagnetic field was studied and the experimental results are shown as the following. The primary α-Mg grains are refined obviously when the slurry is stirred by a rotational electromagnetic field during continuously cooling and they are eventually changed to fine rosette grains or spherical grains. If the above semi-solid slurry is further stirred isothermally for some time, much more spherical primary α-Mg grains can be obtained. If the melt is first cooled down to a given semi-solid temperature and then starts being stirred by the rotational electromagnetic field, the primary α-Mg dendrites will be large, and a longer time will be taken and a larger stirring power will be needed for the secondary arms of the dendrites to be remelted on the roots to prepare an ideal semi-solid slurry. Theoretical analysis indicates that the strong flow motion leads to a more even temperature field and a solute field and stronger man-made temperature fluctuation in the AZ91D magnesium alloy melt so that the spherical primary α-Mg grains are increased in the slurry. Moreover, all the measures promoting the temperature fluctuation will be favorable to the formation of spherical primary α-Mg grains and all the factors increasing the arm's root remelting difficulty will be favorable to the formation of rosette-type primary α-Mg grains.
关键词:
AZ91D magnesium alloy
,
null
,
null
张冀
,
徐淑强
,
李青
功能材料
以磷酸盐化学转化膜为研究体系,采用动电位极化和交流阻抗分析方法及检测手段,研究乙醇胺添加剂及其浓度对AZ91D镁合金磷化膜耐蚀性能的影响.研究发现,(1)乙醇胺(MEA)作为添加剂可有效改善AZ91D镁合金表面磷化膜的耐蚀性能.在MEA添加量为1.2g/L时,磷化膜的耐蚀性最好.添加乙醇胺1.2g/L时制备的磷化膜,在3.5%(质量分数)NaCl溶液中的耐蚀性能比AZ91D镁合金基体提高了10倍;(2)MEA浓度在0.4～1.2g/L时,磷化膜的R_(ct)随MEA浓度增加成线性增长关系.MEA浓度1.2g/L时达到最大值.磷化膜的R_p在MEA浓度为1.2g/L时达到最高值.当MEA浓度继续增加时,R_p明显下降.MEA浓度控制在0.8＜C_(MEA)＜1.6g/L时获得的磷化膜的耐蚀性能最好.
关键词:
AZ91D镁合金
,
磷化膜
,
耐蚀性能
,
电化学测试
游国强
,
王向杰
,
齐冬亮
,
郭强
,
龙思远
材料工程
doi:10.3969/j.issn.1001-4381.2013.10.010
通过显微组织观察、晶粒尺寸定量分析、显微硬度测试和拉伸实验等手段,系统研究了线能量变化对热挤压AZ91D镁合金钨极氩弧焊接接头微观组织、显微硬度和极限抗拉强度的影响.结果表明:线能量过低时,焊缝易出现未焊透和气孔缺陷,随着线能量的增加,熔合区和热影响区的晶粒尺寸均增大.线能量的增加导致热影响区和熔合区中的低熔共晶产物由连续状向颗粒状转变.适当的增加线能量有助于提高焊接接头平均显微硬度和极限抗拉强度,但过高的线能量会导致焊接接头的平均显微硬度和极限抗拉强度下降.这是因为当线能量增大到一定程度时,晶粒尺寸(霍尔-佩奇效应)、锌元素蒸发和过时效对金属材料强度产生的作用大于弥散强化(奥罗万强化机理)对材料强度产生的影响,霍尔-佩奇效应对材料性能的影响占主导地位.
关键词:
AZ91D镁合金
,
钨极氩弧焊
,
显微组织
,
极限抗拉强度
王开
,
何乃军
,
翟彦博
,
刘昌明
机械工程材料
通过降低浇注温度来制备半固态料坯,再将料坯重熔至半固态,最后运用高压铸造技术成型摩托车用AZ91D镁合金零件;用光学显微镜、拉伸试验机和硬度仪等研究了成型零件的显微组织和力学性能.结果表明:半固态料坯的组织由初生α-Mg相、次生α相和γ-Mg_(17)Al_(12)相共晶组织构成,降低浇注温度可使组织细化;重熔后组织由未熔的α-Mg 固熔体和部分液相转变相组成;经过半固态高压铸造成型后,零件显微组织由未熔的α-Mg相与网状分布的共晶相组成;用该工艺制备零件的力学性能受到组织缺陷和铸件内部缺陷的影响较大,需要进一步优化半固态成型工艺.
关键词:
AZ91D镁合金
,
显微组织
,
半固态高压铸造
,
力学性能
刘秋月
,
张修庆
,
浦海洲
,
徐金鹏
表面技术
doi:10.16490/j.cnki.issn.1001-3660.2015.02.007
目的：提高AZ91 D镁合金的耐腐蚀性能,扩大其应用范围。方法先在AZ91 D镁合金表面化学镀Ni-P镀层,再化学镀Ni-Sn-P镀层,形成Ni-P/Ni-Sn-P双镀层。研究Ni-P/Ni-Sn-P双镀层的表面形貌和耐腐蚀性能,并与Ni-P单镀层进行对比。结果 Ni-P/Ni-Sn-P双镀层表面分布更均匀平整,缺陷较少,孔隙率较低,具有无定形结构。二次Ni-Sn-P镀层的腐蚀电位约为-0.77 V,略低于一次化学镀Ni-P层(约-0.68 V),两镀层间的电位差使得其构成了微腐蚀电偶,Ni-P层作为阴极,Ni-Sn-P层作为阳极,阳极优先被腐蚀。结论 Ni-P/Ni-Sn-P双镀层的Ni-Sn-P外层能为Ni-P内层提供阴极保护,较好地横向分散腐蚀电流,从而增强AZ91 D镁合金基底的耐腐蚀性能。
关键词:
AZ91 D镁合金
,
Ni-P镀层
,
Ni-P/Ni-Sn-P双镀层
,
耐腐蚀性能
王亚军
,
张涛
,
罗杰
机械工程材料
采用由滑轮增力机构和液压增力机构组成的二级增力机构加载的稳态热流方法,通过自制的界面接触换热系数测量装置对AZ91D镁合金/H13模具钢界面的接触换热系数进行了研究,分析了接触面载荷和温度对界面接触换热系数的影响.结果表明:当接触面载荷较低时,随载荷的增大,接触换热系数变化较为显著,在高载荷区域接触换热系数对载荷的敏感性有所下降;接触面温度越高,接触换热系数越大,在320～370℃温度范围内,界面接触换热系数随温度升高的变化不明显,越过此阶段后又随温度升高而增大.
关键词:
接触换热系数
,
AZ91D镁合金
,
H13模具钢
,
接触面载荷
,
接触面温度
贾理男
,
梁成浩
,
黄乃宝
,
段峰
,
王利霞
稀有金属
采用交流脉冲沉积法在AZ91D镁合金表面合成了羟基磷灰石涂层.考察了交流脉冲电压、沉积时间及电解液添加剂等电化学沉积参数对羟基磷灰石涂层的形貌、微观结构、元素组成及电化学性能的影响.结果表明,当脉冲电压为11oV时,纳米级别的羟基磷灰石涂层表面更为均匀,孔隙度更小,且其XRD的特征衍射峰更为突出.当电解液中添加了NaNO3和H2O2后,羟基磷灰石颗粒和涂层表面形貌均得到优化;同时,极化曲线和交流阻抗测试结果表明该涂层在模拟体液中的耐蚀性能提高.浸泡实验结果表明,该涂层有利于诱导羟基磷灰石的形成,从而提高涂层的生物活性.
关键词:
AZ91D镁合金
,
交流脉冲沉积
,
羟基磷灰石
,
生物活性涂层
徐宏妍
,
李智勇
中国腐蚀与防护学报
在自来水和3.5％NaCl溶液中测试了铸造AZ91D镁合金与铝合金、锌合金、Q235碳钢和Cu偶合后的电偶腐蚀行为,研究了腐蚀环境、偶接材料和阴阳极面积比(CAAR)对铸造AZ91D镁合金电偶腐蚀行为的影响.在电偶腐蚀过程中测量溶液的pH值以及电偶腐蚀电流；用失重法计算了铸造AZ91D镁合金的电偶腐蚀速率,利用SEM观察了AZ91D镁合金的腐蚀形貌,并对腐蚀产物进行XRD分析.结果表明,AZ91D镁合金在电偶腐蚀过程中会使溶液的pH值升高,并伴有以Mg(OH)2为主的腐蚀产物的生成；溶液中Cl-的存在会加速AZ91D镁合金的电偶腐蚀速率；低氢过电位金属Q235碳钢和Cu对AZ91D镁合金的电偶腐蚀加速效果明显高于中氢过电位金属铝合金和锌合金,偶接材料的极化性能对AZ91D镁合金的电偶腐蚀速率有较大影响.同时,大的阴阳极面积比会加速AZ91D镁合金的电偶腐蚀速率,且AZ91D镁合金的电偶腐蚀电流随阴阳极面积比的增大而呈线性增长趋势.
关键词:
AZ91D镁合金
,
电偶腐蚀
,
偶接材料
,
阴阳极面积比
