高强度热成形钢板冷却速率-强度-硬度预测

基于高强度钢板热成形平板模具分区冷却试验获得了淬火过程阶段冷却速度对机械强度-硬度的影响规律。采用量纲分析法建立了热成形材料冷却速率-机械强度-硬度指数模型,并验证了该模型的有效性。通过编制用户子程序将该模型引入自主开发的KMAS_HF软件平台中,实现了对典型U形热成形产品淬火后强度硬度的数值仿真预测。结果表明:该模型对热成形高强度钢淬火后机械性能仿真预测具有较好的适用性,为实现梯度硬度复合热成形工艺优化及产品性能分析提供了一种新的仿真分析流程。     

中空电极板对狭缝式聚合物熔体微分电纺的影响

研究了电极板中空结构对熔体微分电纺过程的影响,探讨了中空宽度对射流数量、射流间距、纤维直径及均匀性的影响。结果表明:电极板采用中空结构时纺丝模头上所产生的射流数量多于实心电极板,且可有效提高电场击穿电压,验证了中空结构的可行性;电极板采用中空结构后,纤维平均直径及直径均匀性均有明显提高,但随着中空宽度继续增加,射流数量减小,射流间距及纤维平均直径增加且直径均匀性变差,从实验研究结果可知,电极板增加中空结构可提高纺丝效果及质量,但中空宽度不宜过大。     

Microstructure characterization of reinforcements in in-situ synthesized composites of Al-Zr-O system

A novel in-situ reaction system Al-Zr-O was developed. In-situ Al3Zr and Al2O3 particulates reinforced aluminum matrix composites were fabricated by the direct melt reaction technique in the Al-Zr-O system. Microstructures of the composites and crystal morphology of in-situ formed Al3Zr and Al2O3 particulates were analyzed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Results indicate that in-situ formed Al3 Zr and Al2O3 particles are finer and well distributed in aluminum matrix. Al3Zr particulates with a tetragonal structure are mainly in the shape of polyhedron. A few of them are in the form of rectangle. The length/width ratio of the rectangular Al3Zr is less than 2.0 and the maximum size is 2μm. In addition, a certain number of Al2O3 submicro particles with a hexagonal structure are also generated in this system. Furthermore, it is found that Al3Zr crystal grows by the mechanism of twinning. The twin plane is (114). The twinning direction is [221]. The tensile tests show that the composites synthesized in the Al-Zr-O system exhibits high strength and ductility. There are a lot of ripples with fine particles on the fracture. The principal strengthening mechanisms for (Al3Zr Al2O3 )p/Al composites may include Orowan strengthening, grain-refining strengthening, solid-solution strengthening and dislocation strengthening.     

AlSi7Mg合金熔体等温处理中组织形态的演变

研究了AlSi7Mg合金在液相线附近不同的温度下保温时，其凝固组织形态的演变规律。在600—650℃之间不同的温度下对AlSi7Mg合金保温30min处理，研究了合金中初生α相的形态随温度改变而演变的过程。试验结果表明：在605—650℃之间保温时，随着保温温度的降低，初生α相逐渐由发达的树枝晶向蔷薇状枝晶和粒状晶转变；在605℃保温30min，可得到尺寸较小、分布均匀的粒状初生α相，在605℃以下保温时，初生α相又开始向蔷薇状形态演变。另外，在605℃下对AlSi7Mg合金进行不同时间的保温处理，结果显示：随着保温时间由10min延长到60min，初生α相的形态经历了由不规则的枝晶到均匀的粒状等轴晶再到蔷薇状组织的转变过程。     

Direct electroless Ni-P plating on AZ91D magnesium alloy

An electroless Ni-P plating treatment was applied on AZ91D magnesium alloy to improve its corrosion resistance. Optimum pretreatment conditions and optimum bath of electroless nickel plating for magnesium alloy were found through many experiments. In order to avoid bother of pre-plating medium layer, a set of procedure of direct electroless Ni-P under the acid condition was investigated. The properties of the coating with 10% phosphorus were investigated. The results show that a coating with high hardness, low porosity and good adhesive strength is obtained. X-ray diffraction patterns show that the structure of the coating is an amorphous phase. After annealing at 400 ℃, the amorphous phase of Ni-P is transformed to crystalline phases, and some intermetallics as Ni3P and Ni5P2 are deposited from Ni -P solid solution along with an enhancing hardness from Hv 450 to Hv 910.     

国际焊接培训可选途径及其实施办法(1)

国际焊接培训体系是国际焊接学会 (InternationalInstituteofWelding ,IIW )在欧洲焊接联合会培训体系的基础上建立起来的 ,自 1998年开始实施以来 ,先后发展了国际焊接工程师 (IWE)、国际焊接技术员 (IWT)、国际焊接技师 (IWS)、国际焊接技士 (IWP)、国际焊接质量检验人员 (IWIP)和焊工 (IW )等培训课程项目。同时 ,为推进世界范围内焊接人员资格的一体化 ,施行过渡措施 ,即具备一定学历、知识水平和工作能力和技术资格的焊接技术人员 ,经过国际焊接学会的评估和批准 ,可以过渡为相应的国际焊接技术资格。如我国自 2 0 0 0年 1月…     

准晶Al_(72)Ni_(12)Co_(16)合金在特殊涂层中的深过冷及其凝固组织

研究了Si Zr B模壳涂层对准晶Al72Ni12Co16合金过冷度与凝固组织的影响规律。通过使用Si Zr B涂层模壳,在Al72Ni12Co16合金中获得了不同大小的过冷度,其最大值达到195K。根据经典形核理论,计算了熔体与涂层内壁间的润湿角。研究结果表明:Si Zr B涂层对过冷准晶Al72Ni12Co16合金熔体具有较强的抑制形核作用,因而可使大体积合金熔体获得深过冷。     

我国线材品种质量的优化与展望

从线材用户的角度论述了近十年来我国线材生产取得了长足的进步，但与国外先进水平相比仍存在着质量、品种上的差距。展望未来十年，提出应提高高碳钢及特殊钢线材比例，对尚不能满足要求的产品品种、质量应再优化。由此建议再建１０条高速线材生产线，最好引进１～２条更高水平的高速线材轧机。     

基于递归小波与ART2网络的刀具状态智能监测

为实现刀具的实时状态监测,以超高斯函数为基础,构造出一类用递推公式进行小波变换的小波基,提出该系列小波基的优化方法,对其时频特性进行了分析.对刀具AE信号进行递归小波分解,提取特征并应用ART2网络识别刀具状态.结果表明,基于递归小波与ART2网络的刀具状态监测具有鲁棒性强、实时性好的特点.