TC11钛合金棒开裂原因分析

TC11合金钛棒在退火后发现裂纹。为分析裂纹产生的原因,对其进行了裂纹宏观和微观检验、显微硬度测试和能谱分析。结果表明：原材料在冶炼过程中氧、碳含量偏高聚集在材料中形成偏析,在轧制过程中开裂,退火后发现的钛棒纵表面的裂纹是由原材料带来的。     

钛合金表面激光熔覆Co-WC复合涂层的组织及力学性能

在钛合金TC4(Ti-6Al-4V)表面利用激光熔覆Co-WC复合涂层,利用扫描电镜(SEM)、能谱分析仪(EDS)和硬度计研究涂层的微观组织及力学性能。结果表明,Co+15%WC、Co+30%WC及Co+45%WC试样熔覆层与基体都实现了冶金结合,表层激光熔覆层涂层内组织均匀致密,没有气孔、裂纹等缺陷。而Co+60%WC试样虽然熔覆层与基体界面也为冶金结合,但是熔覆层内发生了开裂。激光熔覆Co-WC复合熔覆层的宏观洛氏硬度较TC4基体提升了2~3倍,合金粉末中WC的含量比例越高,熔覆涂层试样的宏观洛氏硬度的提升越明显。4种熔覆试样从基体到熔覆层表面,其显微硬度都是逐渐升高的趋势,熔覆层表面显微硬度达到TC4基体的显微硬度的近3倍。在Co基合金粉末中添加WC的最大含量为45%,高于45%之后,熔覆层显微硬度值下降。     

激光洛氏及表面洛氏硬度副基准

中国计量科学研究院于1981年研制成功激光洛氏及表面洛氏硬度副基准，并于1986年被批准为副基准。激光洛氏和表面洛氏硬度副基准都是应用激光双光程干涉原理测量压入深度，激光洛氏硬度副基准包括洛氏硬度机和一组基准金刚石压头组，激光表面洛氏硬度副基准包括麦面洛氏硬度机和一组基准金刚石压头组。语氏硬度测量在工业生产和国防建设中应用广泛，是最主要的硬度试验方法之一，如差一个洛氏硬度单位（HR），就会对轴承、刀具、齿轮、武器等的寿命产生较大的影响；表面洛氏硬度测量是检查产品质量、测定材料机械性能以及确定合成T艺的主…     

准确测试SA-213M T22钢薄壁管洛氏硬度的方法

某批次薄壁SA-213M T22钢管洛氏硬度测试结果偏低,通过室温拉伸试验和采用5种方法进行洛氏硬度测试,结合室温拉伸试验结果对不同洛氏硬度测试方法进行了对比分析。结果表明:如果直接在薄壁钢管表面进行表面洛氏硬度测试或洛氏硬度测试,管壁支撑不足会造成试样变形导致测试结果偏低;如果薄壁钢管中间加圆柱支撑,由于不能确保压头轴线和载荷加载方向与钢管表面垂直,且钢管外表面与贴合的圆柱支撑有间隙钢管圆弧面与贴合的圆柱支撑面存在间隙,也会造成测试结果偏低。采用将钢管取样镶嵌抛光后将测得的维氏硬度转换为洛氏硬度的方法,或者采用去除钢管表面氧化皮和脱碳层并在外表面加工出试验平面并镶嵌后,将测得的表面洛氏硬度转换为洛氏硬度的方法,得到的洛氏硬度测试结果比较准确。     

洛氏硬度计压头对示值的影响

硬度计压头对硬度示值影响很大,本文分析了洛氏硬度及表面洛氏硬度两种压头几何尺寸偏差的影响量,并提出了使用中压头的检查方法.     

建筑钢结构用钢材硬度与强度之间的关系

通过回归分析方法研究了建筑钢结构用钢材硬度(洛氏硬度、维氏硬度和布氏硬度)与强度(上屈服强度和抗拉强度)之间的关系,给出了用硬度推算强度的换算公式及换算偏差,并与GB/T 33362-2016和GB/T 1172-1999进行了对比。结果表明:建筑钢结构用钢材的硬度与强度之间呈正相关关系,用布氏硬度换算的抗拉强度的相对偏差明显低于洛氏硬度和维氏硬度的。GB/T 1172-1999给出的用洛氏硬度换算的抗拉强度和维氏硬度换算的抗拉强度与试验结果较为接近。考虑现有便携式硬度检测仪器及样品处理设备,采用洛氏硬度和布氏硬度推算钢材强度在实际工程中具有可操作性。     

QCr0.5铬青铜带布氏、洛氏、韦氏硬度、强度的对比测试与换算

通过对大量的QCr0.5铬青铜带进行布氏硬度、洛氏硬度、韦氏硬度和屈服强度、抗拉强度对比测试试验,研究了QCr0.5铬青铜带各种硬度及强度之间的换算关系。结果表明:QCr0.5铬青铜带布氏硬度与洛氏硬度和韦氏硬度之间均符合线性关系;而布氏硬度与屈服强度和抗拉强度之间存在阶段性线性关系,当其布氏硬度高于115HBW时屈服强度和抗拉强度显著提高。     

影响马口铁表面洛氏硬度测定值的几个因素

马口铁(镀锡铁皮)的调质度是以其表面洛氏硬度值来表示的,它是一项重要的性能指标,在马口铁加工使用中起重要作用.因此,在大量进口马口铁检验中,经常涉及到其表面洛氏硬度值的测定问题.表面洛氏硬度的测试原理与普通洛氏硬度相同.区别仅在于施加的载荷不同.表面洛氏硬度的测定是用金刚石圆锥或钢球作压头,在29.4N初载荷和147.1N,294.2N,441.3N总载荷作用下压入试样.马口铁一般规定测试表面洛氏硬度HR30T.即使用(?)1.588mm(1/16″)钢球压头及294.0N载荷.本文就实际检验过程中影响该硬度值测试准确性的几个因素进行归纳和分析,供大家参考.     

6061铝合金ECAP变形后的微观组织和硬度

对经过固溶时效处理的6061铝合金在室温下进行了4道次挤压。采用光学显微镜分析了试样ECAP变形前后的显微组织变化,采用洛氏硬度计对6061合金ECAP变形前后进行了硬度测试。结果表明:ECAP工艺不仅能够细化6061铝合金晶粒,而且可提高6061铝合金硬度,经过2道次挤压后,合金洛氏硬度有了较明显的提高,但在随后道次的变形中,合金的洛氏硬度呈缓慢的下降趋势,并且随着变形道次的增加,挤压试样的各部分洛氏硬度值趋于一致,挤压试样各部分变形趋于均匀。     

硬度测试技术的新动态与发展趋势

对目前国际上硬度测试技术的最新发展与趋势进行了分析研究，简要介绍了宏洛氏硬度、超微压痕硬度及世界统一的洛氏硬度标尺等试验方法，并对今后硬度测试技术的发展和趋势进行了预测。     

汽轮机高压外缸结合面双头螺栓断裂分析

某电厂汽轮机高压外缸结合面双头20Cr1Mo1VTiB钢螺栓在安装时发生断裂,通过断口分析、化学成分分析、金相检验以及力学性能测试等方法对螺栓的断裂原因进行了分析。结果表明:该螺栓钢存在严重的显微组织缺陷,力学性能指标不符合技术条件要求,减弱了螺栓的承载能力,螺纹处的应力集中效应会加剧螺栓的缺口敏感性,导致螺栓在安装时于螺纹处发生脆性断裂。     

硼砂对自蔓延高温合成ZrB2粉体的影响

以ZrO_2、Mg、B_2O_3及Na_2B4O_7为原料,采用自蔓延高温合成技术制备ZrB2粉体。通过FactSage7.0软件计算,从热力学角度研究了该反应体系发生自蔓延反应的可能性。采用X射线粉末衍射物相分析仪、场发射电子扫描电镜-能谱分析对最终产物的物相组成及显微形貌进行检测。分析结果显示,过量的Mg、B_2O_3可有效提高产物中ZrB_2的含量,Mg和B_2O_3分别过量40%(质量分数)、30%(质量分数)为Mg-ZrO_2-B_2O_3体系的较佳配比。基于上述优化配比,研究了用无水硼砂(Na_2B_4O_7)替换原料中B_2O_3对产物ZrB_2含量及晶粒尺寸的影响,当替换量达到15%(质量分数)时,ZrB_2的含量最高,并且随着Na_2B_4O_7替换量的增加,产物的晶粒尺寸由2μm减小至不足0.5μm。     

Influence of the accumulated error in thread pitch on the stress–strain state and cyclic strength of threaded joints

Using the finite element method, the analysis of influence of errors in pitch during the thread production on the behavior of stress distribution in stud–nut joints is performed. The value of maximum local stresses in studs of a threaded joint is shown to substantially depend on errors in thread pitch of a stud and a nut. On the basis of the analyses of stresses and strains under cyclic loading, fatigue curves are plotted for the threaded joints having deviations in thread pitch. It is shown that, with a rational selection of the deviation in pitch, the cyclic strength of threaded joints can be considerably increased. The results of analysis agree satisfactorily with the data of fatigue tests of the M39 × 3 threaded joints.     

Influence of tool geometry and rotational speed on mechanical properties and defect formation in friction stir lap welded 5456 aluminum alloy sheets

Friction stir welding of AA5456 aluminum alloy in lap joint configuration is with two different tempers, T321 and O, and different thicknesses, 5 mm and 2.5 mm was investigated. The influences of tool geometry and various rotational speeds on macrostructure, microstructure and joint strength are presented. Specifically, four different tool pin profiles (a conical thread pin, a cylindrical–conical thread pin, a stepped conical thread pin and Flared Triflute pin tool) and two rotational speeds, 600 and 800 rpm, were used. The results indicated that, tool geometry influences significantly material flow in the nugget zone and accordingly control the weld mechanical properties. Of particular interest is the stepped conical threaded pin, which is introduced for the first time in the present investigation. Scanning electron microscopy investigation of the fracture location of samples was carried out and the findings correlated with tool geometry features and their influences on material flow and tension test results. The optimum microstructure and mechanical properties were obtained for the joints produced with the stepped conical thread pin profile and rotational speed of 600 rpm. The characteristics of the nugget zone microstructure, hooking height, and fracture location of the weld joints were used as criteria to quantify the influence of processing conditions on joint performance and integrity. The results are interpreted in the framework of physical metallurgy properties and compared with published literature.     

固相原料反应生成碳化硅晶须的实验研究

实验研究了三种碳原料和七种硅原料反应生成ＳｉＣ晶须工艺过程，结果表明，反应生成碳化硅晶须的固相原料中，除稻壳外，白炭黑作为硅源，喷雾炭墨作为碳源，加入适当催化剂也可以得到高品位碳化硅晶须，纯度在９５％以上，生成率在２５％以上。     

TiC/Fe-Al原位复合材料制备及其显微结构

本文研究了用废弃的钢和球墨铸铁以及钛铝添加剂为原料,经熔炼和热处理制备TiC/Fe3Al复合材料的工艺过程.用光学显微镜、XRD等方法观察了复合材料的相组成、显微结构(TiC颗粒的大小和形状),进而分析了原料成分、热处理时间和温度对原位反应、TiC颗粒的生成及显微结构的影响规律.     

Overlaying welding technology and performance of axle tube remanufacturing

Screw failure is one of the main scrap forms for rear axle tube, and thread turning after surfacing is a common means of remanufacturing. This paper takes rear axle tube as the main research topic, which is made of 40Mn and provided by an axle company. Manual electric arc welding, CO2 shielded arc welding and argon shielded arc welding are carried to overlay the damaged thread. The deposited metal consists of two welding material lays.Welding process and overlay properties are characterized by the test and analysis of microstructure, residual stress and hardness of surfacing layers. The results show that
argon shielded arc welding is an effective method to repair the failure thread; its microstructure of fusion area is meticulous and uniform; its residual compressive stress (absolute value) of welding surface is the biggest among the three welding methods; its hardness curve is relatively flat and appropriate for turning.     

φ165.1mm钻铤内螺纹接头失效分析

对内螺纹接头失效的钻铤进行了化学成分、力学性能和显微组织分析,并采用扫描电镜和X射线能谱仪对断口形貌及夹杂物成分进行了分析,找出了钻铤内螺纹接头失效的原因。结果表明:该钻铤内螺纹接头失效为早期疲劳失效;导致其疲劳失效的主要原因有钻铤内螺纹根部加工不光滑,使该处在交变载荷作用下应力集中严重,首先萌生微裂纹成为疲劳源;钻铤内螺纹型号和内外径尺寸不合标准要求以及材料中含有数量较多的MnS夹杂物也都大大降低了其疲劳性能,加速了疲劳裂纹的萌生和扩展。     

Effect of fine-grained raw material addition on microstructure refinement and tensile properties in horizontal continuous casting Al–12%Si alloy billets

Horizontal continuous casting (HCC) Al–12%Si alloy billets were prepared using fine-grained Al–12%Si as a raw material. The influence of this fine-grained raw material on the microstructure and tensile properties was studied. The uniformity of the HCC Al–12%Si alloy billets was also analyzed. The results show that the fine-grained raw material can effectively reduce macrosegregation and make both the α-Al and eutectic silicon much finer. The ultimate tensile strength and elongation clearly increased with an addition of 30% fine-grained raw material compared to the HCC alloy billets with no addition of fine-grained raw material. However a small decrease nonetheless occurred after an addition of fine-grained raw material up to 50%.     

Failure Investigation of Counterweight Separation from Aircraft Propeller

The counterweight of a propeller in a turboprop aircraft was separated during an engine run-up inspection. If this separation occurs in-flight, it may result in an accident involving serious damage or injury. In this investigation, the failed counterweight clamping assembly was studied to determine the root cause of failure. Both experimental and computational investigations were performed to explore and confirm the effects of experimentally observed anomalies on potential clamping assembly failure. Dimensional measurement of the failed clamping thread area by X-ray CT scanning revealed significant deviation from requirements in the major diameter of the thread. Fractographic and microscopic examination along with chemical analysis confirmed that the clamping bolts were pulled out due to overload stripping failure of the internal threads. Detailed computational fracture modeling utilizing the XFEM crack simulation technique provided further insight proving that thread engagement length had a significant effect on the clamping assembly failure. Based on these observations, it was concluded that the main root cause of the stripping failure was the dimensional nonconformance of the internal thread from the requirements in standard 7/16-20UNF-3B that resulted in the loss of thread engagement length.