Analysis of chill-cast NiAl intermetallic compound with copper additions

This study carried out a characterization of chill-cast NiAl alloys with copper additions, which were added to NiAl, such that the resulting alloy composition occurred in the β-field of the ternary NiAlCu phase diagram. The alloys were vacuum induction melted and casted in copper chill molds to produce ingots 0.002 m thick, 0.020 m wide, and 0.050 m long. X-ray diffractometry (XRD) and transmission electron microscopy (TEM) performed in chill-cast ingots identified mainly the presence of the β-(Ni,Cu)Al phase. As-cast ingots showed essentially no ductility at room temperature except for the Ni₅₀Al₄₀Cu₁₀ alloy, which showed 1.79% of elongation at room temperature. Ingots with this alloy composition were then heat treated under a high-purity argon atmosphere at 550 °C (24 h) and cooled either in the furnace or in air, until room temperature was reached. β-(Ni,Cu)Al and γ′(Ni,Cu)₃Al were present in specimens cooled in the furnace and β-(Ni,Cu)Al, γ′(Ni,Cu)₃Al plus martensite-(Ni,Cu)Al were present in specimens cooled in air. Thermogravimetric analysis indicated that martensite transformation was the result of a solid-state reaction with M _s ∼ 470 and M _f ∼ 430 °C. Tensile tests performed on bulk heat-treated ingots showed room-temperature ductility between 3 and 6%, depending on the cooling media.     

低频电磁水平半连续铸造中磁场的分布及其对宏观偏析的影响

采用数值模拟的方法研究了低频电磁水平半连续铸造7075铝合金中不同强度及频率的磁场在熔体中的分布,并采用试验的方法研究了不同条件的磁场对铸锭宏观偏析的影响.将使用传统水平半连续铸造生产出的铸锭与低频电磁水平半连续铸造生产的铸锭进行了比较.研究结果表明:在传统水平半连续铸造工艺条件下,铸锭中易出现较严重的负偏析及重力偏析;然而,在低频电磁水平半连续铸造过程中,低频电磁场的存在明显削弱了铸锭中的宏观偏析.此外,磁场在熔体中的分布情况将直接影响其作用效果,提高磁场强度及适当降低磁场频率均有利于对宏观偏析的改善.     

EFFECT OF LOW-FREQUENCY ELECTROMAGNETIC FIELD ON THE AS-CASTING MICROSTRUCTURES AND MECHANICAL PROPERTIES OF HDC 2024 ALUMINUM ALLOY

The influences of the low frequency electromagnetic field on the horizontal direct chill casting process were investigated experimentally. Ingots of 2024 aluminum alloy with a cross size of 40 mm× 200 mm were produced by the conventional horizontal chill casting process and low frequency electromagnetic horizontal chill casting processre- spectively. The as-cast structures and the mechanical property of the ingots were examined. The results showed that the low frequency electromagnetic field could sub- stantially refine the microstructures and pronouncedly reduce the macrosegregation in the horizontal direct chill casting process. Moreover, the surface quality of the ingot was prominently improved by the low frequency electromagnetic field. The fracture strength and elongation percentage of the ingot was increased with the low frequency electromagnetic field.     

超声处理对2219大规格铝锭微观组织与宏观偏析的影响

在半连续铸造过程中施加超声,成功制备了φ1250 mm 2219铝合金铸锭.利用光学显微镜、扫描电镜、能谱仪及直读光谱仪等仪器对铸锭的组织与成分分布进行检测与分析,探究超声对铸锭组织与偏析的内在作用机制.研究结果表明:超声振动引起的空化和声流效应能明显均匀组织结构,细化晶粒,尤其是心部晶粒细化率达到39.6%.超声促进铸锭晶间第二相呈枝丫状断续分布,晶内析出物点状弥散分布.同时,超声有效减小近表面负偏析,降低边部与心部之间的溶质浓度差异,弱化整个横截面的浓度波动,从而改善宏观偏析.     

Effects of heat treatment on the microstructure and mechanical properties of AA2618 DC cast alloy

Direct chill (DC) cast ingot plates of AA2618 alloy have been increasingly used for large-mold applications in the plastics and automotive industries. The effects of different heat treatments on the microstructure and mechanical properties of AA2618 DC cast alloy were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and hardness and tensile testing. The as-cast microstructure contained a considerable amount of coarse intermetallic phases, including Al₂CuMg, Al₂Cu, Al₇Cu₄Ni, Al₇Cu₂(Fe,Ni) and Al₉FeNi, resulting in poor mechanical properties. Solution treatment at 530 °C for 5 h dissolved the first three phases into the solid solution and consequently improved the mechanical properties of the alloy. By utilizing the appropriate aging temperature and time, different combinations of strength and ductility could be obtained to fulfill the design requirements of large-mold applications. The strengthening of AA2618 DC cast alloy under the aging conditions studied was caused by GPB zones and S′ precipitates. The evolution of both precipitates in terms of their size and density was observed to have a significant effect on the mechanical properties of the alloy.     

北方寒冷地区乡村住宅本土生态技术研究

全面分析北方寒冷地区乡村住宅的现状,综合考虑严寒地区农村经济、技术、生产力发展水平、生态环境等各种因素,从创建生态人居环境的角度出发,研究可操作性强的北方寒冷地区住宅本土生态技术,从而使寒地乡村住宅具有持续发展的能力以及舒适、经济、节能、环保的特质.并根据研究成果建造3栋示范住宅,示范住宅与传统住宅相比节能达55%以上,其中经济型超低能耗住宅节能达80.8%,供暖能源可自给自足,不需要任何费用.该研究将促进北方寒冷地区乡村住宅建设的可持续发展.     

基于云平台的铸钢产品成形工艺设计方法

本文主要介绍了全流程虚拟制造系统云平台在设计铸钢件的成形工艺以及生产过程中的应用,设计人员可利用云平台设计产品的加工余量、砂芯参数、浇注系统、冒口、模具等内容,系统可实现产品工艺设计过程中的公式自动计算,实现工艺人员的快速设计,提高铸造工艺设计的效率和质量.     

3270m^3高炉水冷钢砖的铸造生产工艺

通过对水冷钢砖的结构分析,找出铸造过程中的难点,采用设计合理内冷铁和仿真模拟验证,保证水管不被熔化并形成顺序凝固,采用脱落式芯盒和嵌入式定位,保证螺栓孔、固定栓尺寸位置,采用水玻璃七O砂与铬铁矿砂配合使用,解决螺栓孔难以铸出问题,设计使用专用定位工装,保证各部位尺寸准确,提高铸造质量。     

铸钢件外冷铁标准化技术初探

通过对铸钢件外冷铁标准的制定和应用情况的介绍,提出了节约成本、简化工艺、提高质量的一条重要途径。