脉冲电流对Al及Al-5.3%Zn合金宏观组织的影响

研究脉冲电流作用下凝固的纯Al及Al-5.3%Zn合金的宏观组织变化.实验表明:脉冲电流能够对纯Al及Al-5.3%Zn合金中晶粒的形状和尺寸产生比较显著的影响.与未施加脉冲电流相比,晶粒得到细化、等轴化.脉冲电流作用下剧烈的强迫对流促进晶粒从型壁上游离,增加金属熔体的形核率,晶粒得到细化.     

保温条件下过共晶Al-Si合金半固态浆料的组织演变

研究了保温时间和保温温度对电磁搅拌ZL117合金半固态浆料稳定性的影响.试验结果表明：半固态浆料中初生Si的颗粒直径随着保温时间的延长而逐渐增大,但在前15 min内增长速度比较缓慢,15 min后增长较快;随着保温温度的升高而缓慢增大;初生Si的形状系数随着保温时间的延长而变得越来越大,但也在前15 min内变化较为缓慢,15 min后变大速度突然加快;初生Si的形状系数在620 ℃下保温时最小,在610～620 ℃之间随着保温温度的升高而缓慢变小;在620～650 ℃之间随着保温温度的升高而逐渐增加.     

角过渡曲面对注射模充模时间和锁模力的影响

通过改变塑件局部角过渡曲面，流变性比较分析表明，局部的合理改进，不仅缩短了充模时间，也降低了锁模力。     

Mechanical properties and microstructure of Ti-6Al-4V compacts by metal injection molding

Ti-6Al-4V compacts were fabricated by metal injection molding(MIM). Influence of vacuum sintering time on mechanical properties and microstructure of the sintered compacts at 1 260 ℃ were investigated. The experimental results show that the compacts sintered at 1 260 ℃ for 3 -6 h, which was made from hydrogenation-dehydrogenation(HDH) powder(average particles size is 45 μm), have a relative density of 95.6%- 96.7%, ultimate tensile strength of 648 - 686MPa and 0.2% yield strength of 526 - 615MPa; but a lower elongation(＜4%) and that the compacts sintered at 1 260 ℃ for 2 - 6 h, which was made from 90% gas-atomized powder(average particles size is 32.5 μm) and 10 % HDH powder, have higher relative density(＞95 %), ultimate tensile strength of 800 -848MPa,0.2% yield strength of 712 - 762MPa and high elongation (7.4%- 9.5%). When the sintering time is increased,porosity decreases and microstructure of sintered products changes from equiaxed to typical Widmanstatten, the average sizes of prior β grains, α colonies and α phase thickness in the β grains increase accordingly. After HIP treatment,pores obviously become less, microstructure of alloy is refined and mechanical properties are greatly improved.     

锆－4合金的时间相关低周疲劳

研究了锆－４合金在不同应变速率下的低周疲劳和带应变保持时间相关低周疲劳行为。结果表明：在不同加载方式下，锆－４合金均表现为循环硬化，应变保持和应变速率降低均进一步提高循环饱和应力。应变保持降低材料的疲劳寿命，特别是在高应变幅区域。随着应变速率降低，材料疲劳寿命降低。疲劳变形亚结构观察表明：锆－４合金时间相关疲劳过程中以柱面滑移和晶界滑移方式变形。     

SiCp/Cu复合材料的真空钎焊

对冷压烧结结合热挤压工艺制备的SiC/Cu复合材料,选用Ti和AgCuTi为钎料,采用不同的工艺进行真空钎焊试验.用金相显微镜和扫描电镜对母材和钎焊接头的剪切断口形貌进行分析,利用电子万能试验机对钎焊接头进行抗剪强度测试,将接头抗剪强度与母材抗剪强度进行对比以评判钎缝质量.结果表明,用Ti为钎料连接SiCp/Cu复合材料的连接状况要优于AgCuTi钎料,且连接温度850℃,保温时间为20 min时,抗剪强度最大为70.5 MPa,与母材抗剪强度相当;随着铜基复合材料中SiCp含量不断增加,钎焊接头室温抗剪强度不断下降,当SiCp含量超过10%时,抗剪强度快速下降.     

Role of temperature gradient in liquid／solid phase solution-diffusion bonding

The liquid-film solution-diffusion bonding of ZCuBe2. 5 alloys was conducted using Cu-based alloy powders. The tensile strength of the joint is up to 318 MPa. With the increase of temperature gradient, the bonding time decreases and the interlace migration velocity increases remarkably. The appropriate temperature gradient is 5 -40 K/cm. Under fixed bonding time, the thickness of diffusion layer increases with the increase of temperature gradient, and this tendency becomes more remarkable with the prolonging of bonding time.     

铸钢件的有效浇注时间计算公式

评述了铸钢件在重力浇注条件下，目前常用或一些资料介绍的几种传统的铸件浇注时间计算公式的特点和存在的不足，阐述了作者建立的铸钢件有效浇注时间计算公式的特点及适宜性。     

北满特钢40t-LFV精炼炉真空系统改造

简要介绍了西安重型机械研究所为北满特钢一电炉分厂原有 40 t-LFV设备真空系统进行改造的具体内容。改造后其真空系统不仅能满足不同钢种精炼工艺的要求 ,且真空系统的能耗指标达到世界先进水平     

飞机压力加油系统节流孔径优化控制策略研究

基于飞机地面压力加油系统管路模型，本文采用高级遗传算法（RGA）的排序选择及随机交换算法，在满足管路最大冲击压力及满油时间差的约束条件下，经全局搜索优化策略，得到优化后适应度最佳的节流孔径，试验研究的结果验证了该方法的可行性和有效性。