Microstructure and mechanical behavior of laser aided additive manufactured low carbon interstitial Fe49.5Mn30Co10Cr10C0.5 multicomponent alloy

Laser aided additive manufacturing(LAAM)was used to fabricate bulk Fe49.5Mn30Co10Cr10C0.5 interstitial multicomponent alloy using pre-alloyed powder.The room temperature yield strength(σy),ultimate tensile strength(σUTS)and elongation(εUST)were 645 MPa,917 MPa and 27.0％respectively.The as-built sample consisted of equiaxed and dendritic cellular structures formed by elemental segregation.These cellular structures together with oxide particle inclusions were deemed to strengthen the material.The other contributing components include dislocation strengthening,friction stress and grain bound-ary strengthening.The high εUTS was attributed to dislocation motion and activation of both twinning and transformation-induced plasticity(TWIP and TRIP).Tensile tests performed at-40℃and-130℃demonstrated superior tensile strength of 1041 MPa and 1267 MPa respectively.However,almost no twinning was observed in the fractured sample tested at-40℃and-130℃.Instead,higher fraction of strain-induced hexagonal close-packed(HCP)ε phase transformation of 21.2％were observed for fractured sample tested at-40℃,compared with 6.3％in fractured room temperature sample.     

Methods and mechanisms for uniformly refining deformed mixed and coarse grains inside a solution-treated Ni-based superalloy by two-stage heat treatment

The uniform refinement mechanisms and methods of deformed mixed and coarse grains inside a solution-treatment Ni-based superalloy during two-stage annealing treatment have been investigated.The two-stage heat treatment experiments include an aging annealing treatment(AT)and a subsequent recrystallization annealing treatment(RT).The object of AT is to precipitate some δ phases and consume part of storage energy to inhibit the grain growth during RT,while the RT is to refine mixed and coarse grains by recrystallization.It can be found that the recrystallization grains will quickly grow up to a large size when the AT time is too low or the RT temperature is too high,while the deformed coarse grains cannot be eliminated when the AT time is too long or the RT temperature is too low.In addition,the mixed microstructure composed of some abnormal coarse recrystallization grains(ACRGs)and a large number of fine grains can be observed in the annealed specimen when the AT time is 3 h and RT tem-perature is 980℃.The phenomenon attributes to the uneven distribution of δ phase resulted from the heterogeneous deformation energy when the AT time is too short.In the regions with a large number of δ phases,the recrystallization nucleation rate is promoted and the growth of grains is limited,which results in fine grains.However,in the regions with few δ phases,the recrystallization grains around grain boundaries can easily grow up,and the new recrystallization nucleus is difficult to form inside grain,which leads to ACRGs.Thus,in order to obtain uniform and fine annealed microstructure,it is a prereq-uisite to precipitate even-distributed δ phase by choosing a suitable AT time,such as 12 h.Moreover,a relative high RT temperature is also needed to promote the recrystallization nucleation around δ phase.The optimal annealing parameters range for uniformly refining mixed crystal can be summarized as:900℃×12 h+990℃×(40-60 min)and 900℃×12 h+1000℃×(10-15 min).     

既有石结构民宅外走廊重建置换的加固分析

福建省既有石结构房屋保有量大，石结构房屋由石墙、石柱、石梁和石楼板这四种石构件堆砌组成，结构抗震性能极差。石结构房屋通常设有外走廊，外走廊相对于其他部位较为独立，在地震中和其他环境振动下极易倒塌。在既有石结构房屋未进行抗震加固前，为确保外走廊安全，提出拆除外走廊石构件，采用钢筋混凝土（ＲＣ）结构重建置换的加固方法。设计与分析表明:应当尽可能地增大ＲＣ构件的刚度，以减少地震作用下石结构房屋的侧向位移；ＲＣ构件与相邻的石构件应可靠连接。外走廊ＲＣ构件重建置换的加固方法可为类似石结构民宅加固提供参考。     

MC尼龙重载承压地板井下巷道铺设工艺研究

我国煤矿井下无轨运输混凝土路面铺设成本高，并且受开采应力、巷道底板地质条件等影响，其应用受到限制。重载车辆的频繁碾压极易使路面发生损坏，从而影响正常开采效率还带来高昂的维护费用。为解决这一问题，采用MC尼龙重载承压地板代替传统混凝土铺设路面，进行了MC尼龙重载承压地板井下巷道铺设的工艺研究。通过对承压板井下铺设方案的制定、承压地板型式的研发、地板的整体连接及稳定性研发等，实现了高效的作业效率，更为安全、清洁的作业环境以及更低的成本，进而达到了“以塑代混凝土”的实际示范意义。该铺设工艺为井下无轨运输的采区路面、工作面搬家通道、临时路面以及其他应急路面、硐室地板的应用提供了良好的方案借鉴。     

以金属氧化物为原料改进燃烧法合成γ-LiAlO_2（英文）

提出一种合成γ-LiAlO_2的替代解决方案—改进燃烧法直接合成γ-LiAlO_2,并将其用于相对简单的反应体系中,原料为非氧化性化合物如Al_2O_3和LiOH,燃料为尿素。采用1:1、1.5:1和2:1的非化学计量Li/Al摩尔比,在900和1000°C下反应5 min,制备LiAlO_2,并对其组织和结构进行表征。考察Li/Al摩尔比对材料形貌和高γ射线辐照下材料稳定性的影响。结果表明,所得粉体的晶体结构为?-LiAlO_2和?-LiAlO_2,其取决于Li/Al摩尔比。因此,用该方法可以成功合成微砖状、多面体状和层状?-LiAlO_2,而无需任何后续处理。γ辐照结果表明,所得到的?-LiAlO_2不分解,只形成少量的Li_2CO_3;由此可以确定,辐照会导致固结,不利于氚的有效提取;结果证明,用燃烧法生产高纯度?-LiAlO_2不需要硝酸盐前驱体。     

空间的力量 新奥胡斯大学医院

正新奥胡斯大学医院是丹麦第一个超大型的医院案例,也是一个具有"康复医疗"概念的、超现代的国际先锋作品。医院的建筑设计通过系统运用"信息和循证"的工作方法,践行了"康复建筑"的综合理念。其"信息和循证"的方法是利用对现存建筑的研究和评估,以提供最有效的信息来创建最佳的康复建筑。从单人病房的设计、日光和光线的利用,以及景观和花园空间的设计,旨在尽量满足病人的需求,提升     

大型水电工程前期准备延期的影响类型分析

讨论了成本考虑不足与水电工程项目施工前准备阶段延期的负面影响,以及发展中国家不能及时有效地交付项目与稀有资源浪费间的冲突。建议项目员工、开发商、政府官员和国际金融机构重视延期成本,找到成本与效益的平衡点。     

煤矿井下风水管路压力在线监测系统的研究与应用

为提高井下管路供风、供水的安全性、可靠性，以工业环网作为网络通信平台，通过分站采集数据上传至地面，实现对煤矿井下供风、供水管道的远程实时监控及远程控制，及时发现管网故障，提高维护效率、降低损失，保障供风、供水质量，达到科学预警、降低成本、提高效率的目的。     

白家包滑坡的渗流与稳定性分析

三峡库区是中国地质灾害易发区。为探究库水下降时滑坡的稳定性变化，以白家包滑坡为研 究对象，利用ＧｅｏＳｔｕｄｉｏ软件，建立渗流场－稳定性分析－位移场计算模型，模拟出库水位以不同速度消 落时地下水渗流的消散变化及浸润线滞后库水位的时间效应，深入研究了库水降速下滑坡稳定系数及 滑坡位移场的变化。结果表明:库水下降过程中，滑坡前缘为浸润线变化的重点区域，库水下降降幅增 大，浸润线外凸趋势增强，浸润线滞后于水位线的变化越明显，滑坡受坡体内外水头差动水压力作用，形 成瞬态渗流场，饱和度增加，基质吸力减小，黏聚力、抗剪强度减小，稳定性降低，滑坡前缘位移变形增 加。     

一种军棋机器博弈的多棋子协同博弈方法

针对在军棋博弈不完全信息对弈中，面对棋子不同价值、不同位置、不同搭配所产生的不同棋力，传统的单子意图搜索算法，不能满足棋子之间的协同性与沟通性，同时也缺乏对敌方的引诱与欺骗等高级对抗能力。本文提出一种结合UCT搜索策略的高价值棋子博弈方法，实现高价值棋子协同博弈的策略。实战经验表明:高价值多棋子军棋协同博弈策略优于单棋子军棋博弈策略。