热处理及SiC颗粒尺寸对15%SiC_p/6061Al复合材料性能的影响

采用粉末冶金法制备了体积分数15%的、不同粒度SiC颗粒增强的6061Al基复合材料,研究了固溶-时效热处理工艺对复合材料屈服强度、抗拉强度、延伸率的影响规律,确定了最佳热处理工艺参数,揭示了Si C颗粒(SiC_p)粒度变化对复合材料力学性能的影响规律,研究表明:随SiC_p粒度的增加,SiC_p/6061Al基复合材料的弹性模量基本不受影响;但复合材料的屈服强度、抗拉强度逐渐降低,延伸率、断面收缩率先增大后减小。当SiC_p粒度增加到10μm时,复合材料屈服强度、抗拉强度出现明显下降,同时复合材料延伸率和断面收缩率由提高变为降低,其原因是复合材料断裂失效机制由基体撕裂控制转变为增强颗粒开裂与基体撕裂共同控制。拉伸断口扫描电镜(SEM)分析表明,随着SiC_p粒度的增加,SiC_p/6061Al复合材料中出现颗粒开裂并且数量逐渐增加。     

合金元素对316LN不锈钢的力学性能和点蚀性能的影响

研究了N、Cr、Mo和Ni四种合金元素含量的变化对核电主管道用固溶态316LN不锈钢的晶粒尺寸以及常规力学性能和点蚀性能的影响.随着N含量的升高,316LN的晶粒明显细化,其在固溶处理过程中晶粒长大趋势也减小.N含量的升高可改善316LN的力学性能和耐点蚀性能,但是当N质量分数达到0.20%时,其耐点蚀性能又开始变差.晶粒细化对316LN强度的影响远小于N含量对316LN强度的影响.Cr及Ni含量对316LN的晶粒尺寸及抗拉强度、屈服强度等力学性能影响不大;Cr含量增加可轻微改善316LN的抗点蚀能力,Ni元素对316LN的耐点蚀性能影响不大,但可增大钝态的腐蚀速度从而不利于钝化膜的稳定.随Mo含量增加,316LN的晶粒尺寸略有减小,强度增大,延伸率显著降低,耐点蚀能力改善.      

多孔钛的粉末冶金法制备及其力学性能

采用粉末冶金法成功制备出力学性能与骨匹配的开孔型多孔钛,其孔隙率分布在8.6%～35.4%之间,平均孔径随孔隙率增加而增加;抗压强度随孔隙率的增加而降低,分布在252～848 MPa之间;通过应力-应变曲线计算得到其弹性模量在7.2～9.9 GPa之间,接近人骨弹性模量。此多孔钛有望成为理想的人工骨修复材料。     

热轧中厚板组织-性能预测及软件开发

以热力学和动力学理论为基础,开发了组织性能预测系统,并在首钢中厚板厂实现应用.预测了钢板屈服强度、抗拉强度随工艺及冷却参数的变化,预测结果和实测值吻合较好.随着冷却速率的增加,铁素体体积分数减少,晶粒尺寸变细.同样,成品厚度较大时,铁素体晶粒尺寸较大,铁素体体积分数变化不大.待温厚度为成品厚度的2倍左右,可以使Q235中板获得良好的力学性能.     

等离子喷涂 YSZ 可磨耗涂层孔隙率与力学性能关系研究

本文主要研究了多孔 YSZ 可磨耗封严涂层孔隙率与其力学性能的关系。 采用高能等离子喷涂制备了不同 孔隙率自支撑 YSZ 涂层试样, 采用三点弯曲实验研究了孔隙率与 YSZ 涂层室温和 1060 ℃高温力学性能的关系。 结果表明, 涂层孔隙率在 11.61%~28.80% 之间时, 室温下涂层断裂韧性为 12.48 MPa·m1/2~20.96 MPa·m1/2, 抗弯 强度为 17.10 MPa~43.75 MPa, 弹性模量为 3.64 GPa~13.13 GPa, 1060 ℃下涂层断裂韧性为 9.79 MPa·m1/2~13.71 MPa·m1/2, 抗弯强度为 20.20 MPa~35.12 MPa, 弹性模量为 5.15 GPa~11.00 GPa。 随孔隙率增加, 涂层断裂韧性增加, 抗弯强度、 弹性模量减小。 在中、 低孔隙率下, 涂层在高温下的抗弯强度、 弹性模量和断裂韧性低于室温, 在高 孔隙率下, 高温条件下涂层的抗弯强度、 弹性模量高于室温。 随着孔隙率的增加, 高温条件涂层力学性能的变化 趋势相较室温时更为平缓。     

烧结工艺对多孔TNTZ合金压缩行为的影响

多孔低模量Ti-Nb-Ta-Zr钛合金含无毒元素,且具有优良的生物相容性、强度高、塑性显著等优点,成为目前生物医用植入材料的研究热点。为了提高植入体的骨整合能力,使其与宿主骨实现生物固定,本文采用添加造孔剂的粉末冶金工艺制备基体为β相、含少量第二相的多孔Ti-Nb-Ta-Zr合金。结果表明:随烧结温度的升高和时间的延长,多孔Ti-Nb-Ta-Zr合金的致密度及结合强度增大,但当烧结温度超过1 200℃或时间超过2 h,其压缩弹性模量及屈服强度均下降,这与合金中晶体生长程度及第二相的组成及分布有关。多孔TNTZ合金的压缩断口主要由解理面、棱锥形穿晶断裂面和大量韧窝组成,表明其具有较好的塑性。     

多孔TiNb合金的制备及力学与腐蚀性能研究

本实验采用粉末冶金法制备多孔Ti-35%Nb合金,并对其显微组织、力学及腐蚀性能进行了研究.所制备样品的孔洞分布均匀,孔的连通性好;显微组织主要由β-Ti组成,其压缩曲线表现出典型的开孔泡沫的特征;力学性能能够满足人体多孔骨的移植要求.随着孔隙率的增加弹性模量减小,但强度和腐蚀性能也同时下降.因此,对孔隙率的选择应综合这两方面来考虑.     

热处理温度和应变速率对Ni-22 at%Al-1.0 at%Zr合金拉伸性能的影响

热处理温度通过影响冷轧多晶Ni-22at%Al-1.0at%Zr合金的再结晶体积分数和晶粒尺寸而影响其力学性能.该合金的室温拉伸屈服强度随热处理温度升高而降低;抗拉强度和伸长率先增加后降低,在900℃达到最大值.应变速率并不影响900℃热处理合金的屈服强度,但显著影响抗拉强度和伸长率,这表明该合金仍存在环境脆性.     

Q195带钢成分设计优化及控制

针对Q195带钢强度偏高的问题,对其成分设计进行优化调整。调整后屈服强度、抗拉强度及延伸率全部合格,且控制更加稳定,屈服强度过程能力充分,而抗拉强度的过程能力得到有效提高。调整前后Q195带钢基体组织未发生变化,但成分优化调整后晶粒度级别有所降低,从而使Q195带钢强度普遍下降。且通过有效过程控制,Q195带钢C类和D类夹杂物明显减少而且更加细小弥散,这也是成分调整后钢带延伸率提高的主要原因之一。     

超快冷工艺对高强度含Nb低合金钢组织与性能的影响

通过开展不同冷却速率的对比试验,研究了超快冷工艺对高强度含Nb低合金钢组织与性能的影响。结果表明:相比于常规层流冷却,采用超快冷工艺进行冷却,钢材的屈服强度和抗拉强度均得到提高,伸长率略有下降但幅度不大;随着超快冷冷速的提高,钢材的晶粒尺寸逐渐细化,铁素体、珠光体等高温相变组织比例逐渐减少,贝氏体等中温相变组织比例增加,通过细晶强化和相变强化使得钢材的强度得到增加;同时钢中Nb的析出物数量增多且尺寸逐渐细化,使得钢材的强度得到进一步提高。     

孔隙度对烧结不锈钢纤维多孔材料压缩性能的影响

采用丝径为100μm的不锈钢纤维经松装烧结工艺制备了孔隙度在70%～95%之间的金属纤维多孔板材.在MTS858材料试验机上检测压缩性能,结果表明:孔隙度在82.8%以下的试件的面内应力应变曲线大致分为三个阶段,应变很低情况下的线性弹性区、屈服平台区和应力急剧增大情况下的致密化区,其中屈服平台区较长,说明该材料具有较强的能量吸收能力;随着孔隙度的增加,不锈钢纤维多孔材料的卸载模量、屈服强度减小,其中孔隙度为70%的烧结不锈钢纤维多孔材料的平均卸载模量为5.2GPa,平均屈服强度达到了23MPa;孔隙度大于90.1%的试件屈服强度很低,能量吸收能力很小.     

7075铝合金化学镀对镍磷合金镀膜组织和性能的影响

金属表面处理直接影响7075铝合金的力学性能及耐腐蚀性能.以7075-T6铝合金为基体,采用化学镀(EN)技术在光滑基体表面均匀镀覆一定厚度的镍磷(Ni-P)镀膜,镀膜厚度分别为3.64、5.87和7.33 μm,并通过扫描电子显微镜(SEM)、X射线衍射(XRD)、硬度测试及电化学工作站等手段分析膜层特性及膜厚对70...     

Electrochemical Corrosion and Impedance Studies of Porous Ti–xNb–Ag Alloy in Physiological Solution

Porous titanium (Ti) and its alloys are promising materials for orthopedic applications due to their low elastic modulus, high strength, excellent corrosion resistance, and biocompatibility. In this study, the porous Ti–xNb–5Ag (x = 25, 30 and 35 wt%) alloys were synthesized using the powder metallurgy approach. The effects of Nb content on the porosity, mechanical properties, and electrochemical corrosion behavior of the alloys were investigated. XRD analysis revealed that the porous alloys mainly consist of α-Ti, β-Ti, intermetallic compound (Ti₄Nb), and oxides of TiO₂ and NbO phases. Porous alloys possess the porosity ranging from 57 to 65%, due to the addition of NH₄HCO₃ (45 wt%). Increase in Nb content lead to a reduction in the elastic modulus and compression strengths of the sintered porous Ti–xNb–5Ag alloys. All three developed porous Ti–xNb–5Ag alloys show the optimum combination of elastic modulus and compression strength, which is suitable for orthopedic applications. These porous alloys exhibit excellent electrochemical corrosion resistance in the simulated body fluids, and the samples having low porosity exhibit higher corrosion resistance than high-porosity samples.

     

Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy

Hot-isostatically-pressed powder-metallurgy Astroloy was obtained which contained 1.4 pct, fine porosity at the grain boundaries produced by argon entering the powder container during pressing. The pores averaged about 2μ,m diam and 20 μ m spacing. This material was tested at 650 °C in fatigue, creep-fatigue, tension, and stress-rupture and the results compared with previous data on sound Astroloy. The pores influenced fatigue crack initiation and produced a more intergranular mode of propagation. However, fatigue life was not drastically reduced. A large 25 μm pore in one specimen resulting from a hollow particle did reduce life by 60 pct, however. Fatigue behavior of the porous material showed typical correlation with tensile behavior. The plastic strain range-life relation was reduced proportionately with the reduction in tensile ductility, but the elastic strain range-life relation was little changed reflecting the small reduction in strength divided by modulus for the porous material.     

新型耐腐蚀加热管用不锈钢组织和性能

电热水器用不锈钢材料主要有310S、840等,在使用过程结垢后,容易造成加热管的腐蚀失效。为了解决此问题,针对加热管的服役环境,在310S成分基础上,添加Mo元素,并优化调整了其他合金成分,开发了新型耐腐蚀加热管用不锈钢新材料。研究了新型加热管不锈钢热轧固溶酸洗态的微观组织、力学性能和耐腐蚀性能,并与310S做了对比。利用Thermo-Calc热力学软件分析了新材料在平衡条件下合金组织随温度的变化规律,在900 ℃左右开始析出σ相,但数量不多。在与310S相同轧制规程和热处理规程条件下,新型材料热轧固溶酸洗态的抗拉强度(R_m)、屈服强度(Rp0.2)、伸长率平均值分别为611 MPa、286 MPa、52.8%,强度整体略高于310S,但差别不大,伸长率略低于310S。新材料晶粒度为5.5级,部分区域7级,晶粒度略大于310S,整体上差别不大。新材料和310S平均点腐蚀速率分别为0.49 g/(m2·h)、1.37 g/(m2·h),可见新材料的耐点腐蚀性能明显优于310S。     

蒙乃尔多孔板的力学性能研究

多孔板是流化床布气元件的关键部件。工作中受流动气体和物料的作用,在多孔板上产生一定的压力、拉力和剪切力,因此要求多孔板具有优良的力学性能。采用粉末冶金法制备蒙乃尔多孔板,测定其不同部位的压缩和剪切性能。结果表明:多孔板边部压缩屈服强度可达143 MPa,弹性模量可达18.1 GPa;中心部位压缩屈服强度可达67 MPa,弹性模量可达8.2 GPa;弹性应变区间可达到3.0%;边部剪切强度可达153 MPa,中心为87 MPa。     

Fabrication and properties of graphite fiber reinforced magnesium

Graphite fiber reinforced magnesium composites have been fabricated by infiltration and liquid phase hot pressing techniques. Although pure magnesium does not wet graphite, weting and bonding were achieved by precoating the graphite fibers with titanium. Tensile strengths and elastic moduli of flat rectangular composite specimens were measured and compared with Rule of Mixtures strengths. Significant strengthening and stiffening were achieved. Tensile strength was increased by 170 pct and the elastic modulus by 100 pct. Measured elastic moduli were in good agreement with Rule of Mixtures values. The highest tensile strength was about 83 pct of the Rule of Mixtures strength. It is believed that specimen porosity and fiber misalignment account for the bulk of this difference and that an improved fabrication technique will yield specimens with higher strengths. Fracture modes are presented and discussed.     

A New Resource-Saving, High Chromium and Manganese Super Duplex Stainless Steels 29Cr-12Mn-2Ni-1Mo-xN

 A new family of resource-saving, high chromium and manganese super duplex stainless steels (DSSs), with a composition in mass percent, % of Cr 0.29, Mn 0.12, Ni 2.0, Mo 1.0, and N 0.51-0.68, has been developed by examining the effect of N on the microstructure, mechanical properties and corrosion properties. The results show that these alloys have a balanced ferrite-austenite relation. The austenite volume fraction decreases with the solution treatment temperature, but it increases with an increase in N content. The increases in nitrogen enhance the ultimate tensile strength (UTS) and reduce the ductility of the material slightly. The pitting corrosion potential increases first and then decreases with an increase in nitrogen content when the amount of N arrives to 0.68%. The yield stress and ultimate tensile strength of solution-treated samples were more than 680 and 900 MPa, the elongation of experimental alloys are higher than 30%, respectively, what is more, the pitting potentials were beyond 1100 mV.     

高温温度变化对Q370R钢板的性能影响

对Q370R进行了200～600℃温度下的屈服强度、抗拉强度等高温力学性能试验。通过试验发现,Q370R的屈服强度随试验温度的升高而降低,且温度在接近350℃时,屈服阶段基本消失;抗拉强度在200～400℃时,随试验温度的升高而增加;在400～600℃时,随试验温度的升高而降低。