近液相线半连续铸造法制备半固态铝合金的研究进展

介绍半固态铝合金的各种制备工艺，分析了近液相线半连续铸造法制备半固态铝合金的现状与发展趋势，探讨半固态初生球状晶形成机理的研究现状，指出近液相线半连续铸造法具有广阔的应用前景。     

AlSi_7Mg合金液相线半连续铸造合金组织

采用液相线半连续铸造法,研究了AlSi7Mg铝合金的铸造显微组织.在液相线温度下半连续铸造AlSi7Mg铝合金铸造组织为均匀、细小的近等轴晶组织,晶粒平均等级圆直径为34.5μm,最小直径为5.8μm,最大直径为92μm.晶粒平均圆度为1.88,最小圆度为1.18,最大圆度为5.82.     

垂直半连续铸造Cu-15Ni-8Sn合金组织及性能研究

采用垂直半连续铸造法制备Cu-15Ni-8Sn合金,并对合金的凝固组织、元素偏析以及热处理后的组织和性能进行了分析。采用普通熔铸法制备Cu-15Ni-8Sn合金的铸态组织主要由贫Sn的α-Cu(Ni, Sn)固溶体、富Sn的γ相以及片层状的（α+γ）组成,并且Sn元素主要偏聚在晶界上。在垂直半连续铸造的过程中同时施加机械振动和电磁场具有明显的晶粒细化效果,同时有效减轻了Sn元素的宏观反偏析和微观晶界偏析,富Sn相比较均匀地分布在晶粒内部和晶界上。Cu-15Ni-8Sn合金经过850℃固溶、 90%轧制和400℃时效1 h后可获得最佳的综合性能,此时合金的硬度为HV 401,导电率为8.4%IACS,抗拉强度为1233 MPa,屈服强度为1185 MPa,伸长率为4.5%。     

半连续铸造黄铜铸锭缺陷的产生原因及预防措施

黄铜板、带材因具有良好的物理性能、冷塑性、成型性、焊接性等特点在电气、电子、交通、机械和建筑工业等领域得到了广泛使用,为了确保成品的物理性能和加工性能符合技术要求,本文针对生产过程中黄铜熔铸设备的选型、熔炼工艺、半连续铸造工艺以及铸锭常常见的各种缺陷进行分析和探讨。     

上引法生产阳极磷铜的工业试验

重点介绍上引法生产阳极磷铜的熔炼和铸造新工艺。     

铜合金挤压机推残余振动的消除

分析铜合金挤压机摧残余过程中产生振动的原因，提出消除振动的措施。     

Characterization of Fatigue Substructure of Incoloy Alloy 800 at Elevated Temperature

Transmission electron microscopy has been employed to study the fatigue substructure of Incoloy 800 at elevated temperatures. Substructure parameters such as cell or subgrain intercept size, dislocation density, and misorientation angle between adjacent cells or subgrains were evaluated and correlated with the observed fatigue properties. Observations, results and analysis of substructure data are presented and also discussed in terms of existing theories. Incoloy 800 push-pull fatigue specimens were examined after being tested at various test conditions at 538, 649, 704 and 760 °C. Subboundary intercept size and dislocation density were found to be related to both the saturation stress and the plastic strain amplitude, in accord with the “modified” theoretical predictions and the experimental findings. A critical dislocation density for cell formation was experimentally shown to exist and was found to be strongly temperature dependent. Subboundaries were also found to lie on the low index planes such as {100}, {110}, and {111}.     

Cu-Cr-Zr-Ce合金高温流变应力的研究

利用Gleeble-1500D热模拟试验机对Cu-Cr-Zr-Ce合金在变形温度为600～800℃、应变速率为0.01～5 S-1条件下进行了热压缩试验,测定了其应力-应变曲线,并通过光学显微镜观察了其热压缩过程中的微观组织.结合两者分析了动态回复和再结晶机制.结果表明,动态再结晶是该合金软化的主要机制.     

5A30铝合金板高温拉伸本构关系研究

采用拉伸试样在Gleeble-1500材料热模拟试验机上对5A30铝合金进行高温拉伸实验,研究了该合金在变形温度为300～500℃,应变速率在0.01～10 s-1的高温流变变形行为。结果表明:变形温度和应变速率对该合金流变应力的大小有显著影响。流变应力随变形温度的升高而降低,随着应变速率的增加而升高。5A30铝合金的高温流变行为可用Zener-Hollomon参数描述,从流变应力、应变速率和变形温度的相关性,得出了该铝合金板材高温变形的材料常数和本构方程。计算出5A30铝合金板的变形激活能为Q=201.1 kJ.mol-1,材料常数为A=7.44×1013 s-1,n=4.3135,α=0.02 mm2.N-1;计算得到了5A30铝合金Arrhenius方程;利用双曲正弦模型,得到高温拉伸峰值应力和Z参数的解析式。     

TA32钛合金高温连续氧化行为研究

采用氧化增重法研究了表面有/无喷涂氮化硼高温润滑剂的TA32钛合金在热成形温度为750～850℃范围内的氧化行为,通过SEM和EDS等微观分析方法对氧化层的表面形貌和成分、截面厚度和成分进行分析,并对氧化机理进行探讨。结果表明,氧化温度、时间和氮化硼润滑剂是影响TA32钛合金氧化行为的重要因素。在750～850℃其氧化速率均符合直线-抛物线规律,800℃以上氧化剧烈且发生氧化膜脱落现象;在高温下其氧化膜随着时间逐渐增厚,氧化物由颗粒状变为短棒状和针状,氧化皮逐渐变得疏松多孔。氮化硼润滑剂对TA32钛合金有很好的氧化保护作用,其表面氧化层成分为Ti O2、Al2O3和Ti3Al。     

EDTA分光光度法测定铸造锌合金中铜

试样用盐酸,过氧化氢溶解,在醋酸－醋酸钠介质中,ＥＤＴＡ与Ｃｕ（Ⅱ）生成１＋１兰色配合物,借以进行光度测定,铜量在０－１５ｍｇ／１００ｍｌ范围内符合比尔定律。     

铸造紫铜及铜合金的湿砂型模表面涂料的研究

采用“罗90—1”表面处理涂料的结果表明:操作方便,导热性好,高温不氧化,透气性强,结合不易剥落,表面光洁,保温及润滑性好,能保证金属液应有的流动速度,不需专用工具清砂。基本上解决了原紫铜及铜合金铸件表面或表层质量差的问题,从而使铜铸件表面或表层质量在原75％的基础上再提高20％。     

全层TiAl基合金室温断裂机制的研究

通过拉伸、压缩、弯曲实验分析研究了全层(FL)组织TiAl基合金的断裂机制。研究发现:拉伸和压缩时材料抵抗裂纹的扩展能力不同,抗压强度远高于抗拉强度,这是由于两者的变形及断裂机制不同。TiAl基合金拉伸断裂机制为脆性解理断裂,压缩变形断裂是剪应力和正应力共同作用下的断裂,是准解理断裂。TiAl基合金的缺口弯曲断裂方式也为解理断裂,其断裂过程是先在缺口处产生微裂纹,一旦裂纹在缺口根部产生,由于材料已积累足够的能量使得材料快速失稳解理断裂。     

Tensile Properties and Fracture Behavior of ATI 718Plus Alloy at Room and Elevated Temperatures

The effect of temperature over the range of ambient to 704 °C and strain rate from 10⁻⁴ to 10⁻² s⁻¹ on the tensile properties and fracture behavior of ATI 718Plus was investigated. The results showed that with increase in temperature at a strain rate 10⁻⁴ s⁻¹, there is a small reduction in the yield strength, but a large drop in ductility at 704 °C. This reduction was accompanied by a change in fracture mode from ductile transgranular to brittle intergranular cracking. Detailed analysis of the microstructure and microchemistry of the areas around the crack using electron microscopy showed that the driving mechanism behind the failure at elevated temperatures and slow strain rates is oxygen-induced intergranular cracking, a dynamic embrittlement mechanism. In addition, the results suggest that the δ precipitates on the grain boundaries tend to oxidize and may facilitate the oxygen-induced intergranular cracking. Finally, an increase in strain rate at 704 °C caused a small increase in the yield strength and a huge increase in ductility. This increase in ductility was accompanied by a change in fracture mode from brittle-to-ductile failure. Possible mechanisms for the deformation, failure mechanisms, and strain rate dependence are discussed.

     

SCM822H合金钢高温拉伸性能

研究了SCM822H钢(0．22C-1．1Cr-0．38Mo)700—1100℃拉伸性能。结果表明：温度对SCM822H钢塑性的影响比变形速率和保温时间显著，钢的脆性区为750～950℃(在750—850℃，α相沿粗大的γ相界以薄片状析出；在850—950℃，钢中硫化物延奥氏体晶界析出)，连铸时在此温度区进行矫直容易产生裂纹。     

高温合金表面激光熔铸镍基合金涂层的组织与耐磨性能

研究了高温合金ＧＨ３３表面激光熔铸镍基合金涂层的组织和耐磨性能。结果表明,基材对涂层合金的稀释作用较小;涂层与基材之间形成良好的冶金接合;涂层基体组织为γ－Ｎｉ枝晶,枝晶间为γ－Ｎｉ、Ｍ２３（ＣＢ）６、Ｎｉ３Ｂ、Ｃｒ２Ｂ、ＣｒＢ、ＷＣ等;涂层耐磨性能的平均值较基材提高４倍以上。     

Carbothermic Reduction of Mullite at Elevated Temperature

A systematic investigation was conducted on the reduction of mullite by graphite at high temperatures ranging from 1773 K to 1873 K (1500 °C to 1600 °C) in an Ar atmosphere. The reaction products were identified as Al₂O₃, SiC, SiO, CO, and CO₂. The overall reaction rate was accelerated by increasing the temperature, whereas the atmosphere gas flow rate had no significant influence on the reaction process. The reaction mechanism deducted from the experimental results indicated that the Boudouard reaction was a significant rate-controlling step.     

高温合金熔模铸造车间的工艺设计

从我国高温合金熔模铸造的生产工艺、主要铸造设备入手,以硅溶胶的制壳工艺为例,分析高温合金熔模铸造车间的工艺设计特点,得出合理的工艺布局。并结合生产情况,提出了高温合金熔模铸造车间环境保护的相关措施。