铝对复杂黄铜组织及性能的影响

用光学显微镜(OM)、硬度(HV)和万能试验机对添加不同铝含量(1.5%、2.0%、2.5%、3.0%、3.5%)的复杂黄铜(Cu-22.7Zn-Al-1.0Ni)组织与性能进行了研究.研究结果显示,铝能使合金α相区显著缩小、β相区增加,并起到细化α相、β相的作用,提高合金的抗拉强度、硬度.合金的机械性能随铝含量增加,其抗拉强度和屈服强度提高,而延伸率和冲击韧性下降,当铝含量为3.0%时,0.2 mm Y态板材硬度达到255 HV、抗拉强度达到820 MPa.     

微量钴对铝黄铜组织性能的影响

在铝黄铜(72.5Cu-22.7Zn-3.4Al)中添加微量钴(0.2%,0.4%,0.6%),研究微量钴、熔炼铸造工艺及加工工艺参数对轧制法生产的带材的机械性能的影响。探索采用铝黄铜替代目前广泛使用的弹性铜合金材料-锡磷青铜的可行性。研究结果显示:钴能有效减少铸态合金的晶粒尺寸、改变晶粒的形状,提高合金的抗拉强度、硬度,并保证合金具有较好的延展性。铝黄铜中添加0.4%钴,采用合理的加工工艺生产出的黄铜带具有比锡磷青铜更优异的性能,0.25mm厚的带材,其抗拉强度可达840.4MPa,伸长率为2.8%,维氏硬度值为228,比特硬状态的QSn6.5-0.1带材的抗拉强度最大值(805MPa)提高了4.4%,满足弹性元件的使用要求;同时,由于该黄铜中含有22.7%的锌,可有效降低成本,具有实际应用价值。     

镀铜石墨烯铝基复合材料的制备及性能研究

通过改进的Hummers法制备氧化石墨烯,对氧化石墨烯进行化学镀铜处理。复合材料以纯铝为基体,镀铜氧化石墨烯为增强相。通过放电等离子烧结工艺制备不同质量分数的镀铜石墨烯铝基复合材料。通过扫描电子显微镜(scanning electron microscope, SEM),X射线衍射仪(X-ray diffractometer, XRD)等表征材料的微观组织结构,利用微拉伸试验机测试材料的力学性能。结果表明,镀铜石墨烯质量分数达到0.15%时,镀铜石墨烯铝基复合材料综合性能达到最优,维氏硬度和抗拉强度分别达到56和224 MPa,比石墨烯铝基复合材料的维氏硬度和抗拉强度分别提高6%和24%,比纯铝的维氏硬度和抗拉强度分别提高30%和103%。镀铜石墨烯铝基复合材料具有较好的减磨性。     

稀土元素镧对97W-Ni-Fe合金性能的影响

实验利用氢气烧结工艺制备了97W-Ni-Fe合金,研究了添加不同含量的稀土镧元素对97W-Ni-Fe合金的硬度、冲击韧性、抗拉强度、延伸率等力学性能的影响。实验结果表明:在合金显微组织中,Ni/Fe固溶体沿钨颗粒边缘呈网络分布;在1.0%的添加范围内,随着稀土镧元素添加量的增多,合金硬度呈持续上升趋势,而延伸率则连续下降;抗拉强度先逐渐上升,当镧元素含量超过0.75%则出现下降;冲击韧性先上升,当添加量超过0.25%后出现持续下降。     

热处理工艺对铝基碳化硼板材性能的影响北大核心

选用热等静压法制备的铝基碳化硼板材(B4C体积分数为10.5%,下同),对铝基碳化硼板材进行热处理,测试热处理前后铝基碳化硼板材的密度、硬度、室温力学性能,并观察断口组织。结果表明,热处理后,铝基碳化硼板材的密度几乎相同,硬度显著提高;热处理工艺对铝基碳化硼板材的力学性能有显著影响,其中,经加热(500℃×3 h)、水淬、人工时效(170℃×1 h)后,Al-10.5%B4C板材的抗拉强度为365 MPa,断后伸长率为9.6%,比未热处理板材的抗拉强度提高了89.1%,而伸长率降低了48.3%。     

热处理工艺对铝基碳化硼板材性能的影响

选用热等静压法制备的铝基碳化硼板材(B_4C体积分数为10.5%,下同),对铝基碳化硼板材进行热处理,测试热处理前后铝基碳化硼板材的密度、硬度、室温力学性能,并观察断口组织。结果表明,热处理后,铝基碳化硼板材的密度几乎相同,硬度显著提高;热处理工艺对铝基碳化硼板材的力学性能有显著影响,其中,经加热(500℃×3 h)、水淬、人工时效(170℃×1 h)后,Al-10.5%B_4C板材的抗拉强度为365 MPa,断后伸长率为9.6%,比未热处理板材的抗拉强度提高了89.1%,而伸长率降低了48.3%。     

Al、Ti元素对高锰铝青铜组织和性能的影响

为了解合金元素Al、Ti对高锰铝青铜组织和性能的影响，采用石墨坩埚炉熔炼，制取了Al、Ti含量不同的高锰铝青铜试样，通过对试样进行金相组织检验和硬度测试分析，发现Al、Ti元素含量对高锰铝青铜组织和硬度的影响较大，确定了用该高锰铝青铜材料制造冶金备件产品时，Al元素的最佳含量为7．5％～8．2％、Ti元素的最佳含量为0.20％～0．25％．     

186kA电解槽用铝导杆焊接工艺技术探讨

主要论述铝导杆焊接工艺 ,技术参数对铝导杆使用寿命的影响     

利用人工神经网络研究合金元素对SCM822H钢性能的影响

利用人工神经网络研究了合金元素 C、Cr、Mo和 Mn等对 SCM82 2 H齿轮钢力学性能的影响。研究结果表明 :碳的控制范围一般为± 0 .0 1% ;在 Cr、Mo、Mn的成分范围内 ,增加锰含量可提高末端淬火硬度 ;在抗拉强度和末端淬火硬度未降得很低的情况下 ,增加铬含量可大幅度提高冲击功 ;在末端淬火硬度和冲击功保持不变的情况下 ,增加钼含量可提高抗拉强度     

La,Ce混合稀土对挤压态工业纯铝组织性能的影响

以工业纯铝、Al-10%La中间合金和Al-15%Ce中间合金为原料,利用铝合金熔炼炉制备了Al-x RE(x=0,0.1,0.2,0.3,0.4,0.5;%,质量分数)合金。利用X射线衍射仪（XRD）、扫描电镜（SEM）,能谱（EDS）和背散射电子衍射（EBSD）表征合金相组成、显微组织和织构,通过万能试验机和显微硬度仪测量合金的强度和硬度,将组织、性能和织构进行对比,研究了La,Ce混合稀土对工业纯铝的影响。结果表明：随着稀土含量的增加,合金的平均晶粒尺寸逐渐减小;合金导电率随着稀土含量的增加呈现先增加后减小的变化趋势,其最大值为64.5%IACS,比工业纯铝提高了1%IACS;当稀土含量小于0.3%时,合金的力学性能变化较小,而当稀土含量超过0.3%时,合金的强度和硬度逐渐提高,平均抗拉强度最大值达到90 MPa,平均延伸率最小值为41.6%,平均硬度峰值为HV 24.9,其平均抗拉强度和平均硬度比工业纯铝分别提高了38.5%和19.1%,而延伸率仅降低了9.2%;随着稀土含量的增加,合金中<001>取向的晶粒逐渐减少,<111>取向的晶粒逐渐增多,合金中...     

Guidelines for Warranty Contracting for Highway Construction

This paper presents guidelines for implementing the construction warranty contracting method in the highway construction industry. A logical, step-by-step method for effectively applying the warranty contracting program for use in the highway construction industry is developed. Relevant issues that may present obstacles to the implementation are addressed, while the best practices, compiled from an evaluation of the current industry’s state-of-the-art practices, will assist an interested state highway agency in creating a warranty specification. In performing this research, the current use of warranty specifications among state highway agencies was examined, and an in-depth case study of the Wisconsin Department of Transportation’s warranty program was conducted.     

Considerations for Design Criteria for Lunar Structures

The development of design criteria for lunar structures must begin soon in order to establish adequate criteria. Some of the items that need consideration in such criteria are discussed. The categorization of the structures will provide designers with information on the purpose and level of complexity of the structure. Various construction materials and structure types that will be critical for the design of lunar structures, are considered. The environment of the moon and its possible effects on structures are presented and lead to the development of a few load cases that need to be considered in design. A probabilistic format for the criteria and design lifetimes are also discussed.     

NEHRP Provisions for 1994 for Nonstructural Components

The recently published 1994 National Earthquake Hazards Reduction Program (NEHRP) provisions include new and substantially improved provisions for the seismic design of nonstructural components, including architectural, mechanical, and electrical components. The provisions are a significant departure from the 1991 NEHRP provisions and other seismic provisions, such as those offered by the 1994 Uniform Building Code (UBC). The design-force provisions are rationally derived and consider actual in-structure acceleration data recorded in recent significant California earthquakes. Also considered in the design-force equations are the dynamic properties of the components, the location of the component within the supporting structure, the safety and operational importance of the component, and the component's anchorage ductility and energy-absorption capability. The resulting force requirements of the new recommendations are compared with the 1991 NEHRP provisions and the 1994 UBC requirements. In addition, explicit design displacement provisions are introduced and discussed.     

An argument for colloid resuscitation for shock

A focused review of the physiologic mechanisms of colloid and crystalloid fluid resuscitations for acute critical illness is presented. This review suggests that postresuscitation plasma volume, cardiac output, left ventricular mechanical performance, and global and microcirculatory O2 supplies are more favorable with colloid therapy. Conversely, crystalloid may adversely affect microcirculatory blood flow and resultant O2 supply and use by ischemic tissues in shock. Poor relief of global and regional hypoxia may persist in critically ill patients after resuscitation with crystalloid.