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1.
The as-cast and heat-treated microstructures and mechanical properties of the AZ91 magnesium alloys with and without minor Sc addition were investigated and compared in this paper. The results indicated that adding0.15–0.45 wt% Sc to the as-cast AZ91 alloy not only could modify and refine the Mg_(17)Al_(12) phase but also suppress the formation of the Mg_(17)Al_(12) phase. At the same time, the grains of the Sc-containing as-cast AZ91 alloys were also effectively refined. As a result, the mechanical properties at room temperature(RT) for the Sccontaining as-cast AZ91 alloys were effectively improved. In addition, adding 0.15–0.45 wt%Sc to the AZ91 alloy promoted the formation of the continuous precipitates(CP) during the aging treatment in spite of that the formation of the discontinuous precipitates(DP) was simultaneously suppressed. Accordingly, the Sc-containing as-aged AZ91 alloys obtained the relatively higher mechanical properties at RT than the as-aged AZ91 alloy.  相似文献   
2.
The electrochemical synthesis of polypyrrole (Ppy) coating on AZ31 magnesium alloy was successfully achieved in a solution containing sodium salicylate and monomer of pyrrole through cyclic voltammetry technique. The effect of potential range, passivation pretreatment and number of cycles of polymerization on the quality and protective performance of the coatings was evaluated using surface analysis and electrochemical techniques. Through taking the advantage of charge transfer resistance, current density, corrosion potential, optical microscopy images and SEM micrographs, the optimum condition of synthesis of a Ppy coating with the best adhesion and corrosion protection was determined. The optimal PPy coating synthesized over AZ31 increases the polarization resistance and decreases the corrosion current more than one order of magnitude and shift the corrosion potential about 200 mV toward nobler potentials. The SEM studies showed that Ppy coating have cauliflower morphology of Ppy grains with a diameter ranging from 20 nm to 60 nm.  相似文献   
3.
基于枝晶生长动力学模型(KGT模型),运用晶核自由生长理论计算了在添加细化剂条件下铸态AZ91合金组织的平均晶粒尺寸,并对该模型进行了基于实测数据(以Al-Sr-Mn-Ti-C为细化剂)的有效性分析。结果表明,模型计算值与实测值吻合良好,在细化剂粒子尺寸分布为已知的前提下,利用KGT模型预测异质形核过程中Mg-Al系合金铸态组织的平均晶粒尺寸是可行的。  相似文献   
4.
A small amount of cerium (below 1.0 wt%) addition to AZ91 alloy have been investigated on the hot tearing susceptibility (HTS) at a cooling rate of 1.5Ks?1. The HTS increased to a maximum value with a cerium addition of 0.6 wt% and then decreased to a stable status as cerium was gradually added. Due to high chemical activity, cerium into the melts can react with aluminum to form an Al11Ce3 intermetallic compound. X–ray diffraction results also confirmed the existence of Al11Ce3. The Al11Ce3 increased with the presence of the needle-like and block morphology. As cerium levels increased, the amount of Mg17Al12 decreased. The variations between Mg17Al12 and Al11Ce3 resulted in a similar normal distribution of the HTS in AZ91 alloy. The findings were further verified through the microstructure evolution and the surface morphology of fracture.  相似文献   
5.
由于镁合金AZ31B材料在拉伸与压缩时的力学性能差异,使AZ31B型材在室温下成型规律很难掌握.文章以AZ31B镁合金I型材为研究对象,通过对I型材弯曲过程的数值分析,研究了I型材成型过程与加强筋的高度与厚度的关系,同时对成型过程中的受力、回弹现象及翘曲做了深入的分析,得出了对工程有实用性的结论,可以指导工程实际.  相似文献   
6.
AZ31镁合金薄板温轧过程中引起变形区温度波动的因素较多,因此变形区温度的精确预测是保证轧制工艺及产品质量的关键.本文利用有限元数值模拟软件针对AZ31镁合金薄板温轧过程变形区温度进行了数值模拟,给出了轧辊及轧件的物性参数及模拟的初始条件和边界条件,确定了影响变形区温度的5个关键因素为轧辊温度、轧件温度、轧件厚度、轧制速度及压下率.通过5水平的模拟正交实验方法获取模拟数据,回归了变形区温度数学模型,最后通过一组温轧模拟实验数据测试了数学模型计算精度.  相似文献   
7.
The effects of V-bending process, continuous bending process and combination process on the microstructure and mechanical properties and formability of an AZ31 magnesium alloy sheet were investigated. The experimental results showed that no twins were found in the microstructure of all samples after processes due to the fine grain. The V-bending and continuous bending processes were proved to be an effective approach to modify the mechanical properties and formability. While the samples after the combination process exhibited better mechanical properties and formability than the single processed sample. The yield strength significantly decreased with the value of 100 MPa and the fracture elongation enhanced to 18.3% at room temperature. The Erichsen value was 5.0 mm which was significantly increased by 117% compared with as-received sample. The superior formability of combination processed samples was mainly attributed to the smaller r-value and n-value.  相似文献   
8.
研究了具有较大晶粒尺寸铸轧态AZ31镁合金的高温拉伸性能。通过热处理获得晶粒尺寸d=27.8μm的板材,对不同试样,在温度分别为300,350,400,450℃恒温条件下,以10~(-3)s~(-1)和10~(-2)s~(-1)恒定拉伸速率对试样进行拉伸至失效实验。结果表明,粗晶粒AZ31镁合金在450℃和10~(-3)s~(-1)条件下达到最大的延伸率106.7%。拉伸试样断口形貌的分析表明,450℃时出现丝状物质是合金出现液态Zn的结果。少量的液相可以释放应力集中和协调此时的变形过程。与细晶粒铸轧态AZ31相比,在拉伸条件相同和晶粒尺寸不同的情况下,粗晶粒的塑形较低,其原因是晶界滑移在变形时所作贡献少。  相似文献   
9.
研究了不同浇注温度、辊靴型腔中不同位置的AZ31镁合金组织.结果表明,浇注温度高于750℃时,半固态区减小,工作辊对半固态区枝晶的剪切时间变短,枝晶破碎不充分,得不到优质的半固态金属浆料;浇注温度低于730℃时,固相区变大,半固态区部分枝晶未得到充分剪切就进入了固相区,固相区的枝晶更是难以断裂,因此得不到理想的半固态组织;随着固相区的增加,合金变形更加困难,设备工作压力增加,使用寿命降低;AZ31镁合金连续流变挤压最佳浇注温度为730~750℃.  相似文献   
10.
李清  王立辉 《科学技术与工程》2012,12(17):4057-4060,4068
本文提出了一种基于Galois环振的真随机数发生器设计方法。为了改善随机性,采用了合理的采集手段和后处理方式。该方案采用纯数字电路设计,功耗较低,集成度较高,便于实现。最后基于真随机数测试标准AIS31,对实际设计的真随机数发生器进行了评测,实验结果表明,本设计符合AIS31的测试要求。  相似文献   
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