基于选择性激光烧结技术的快速铸造

介绍了用选择性激光烧结（ＳＬＳ）快速成型技术直接制造覆膜砂铸型（芯）的特点及工艺过程。结合铸件生产,分析研究了ＳＬＳ铸型（芯）的工艺设计、三维实体造型及铸型后处理等过程中所遇到的问题。     

激光快速成型用覆膜砂工艺性能探讨

探讨了激光快速成型用覆膜砂的工艺性能对激光烧结成型、铸型精度和铸件质量的影响，进而得到适用于激光快速成型方法直接制造铸件铸型用的覆膜砂烧结材料。     

烧结陶粒砂在树脂砂中的应用效果

烧结陶粒砂是由耐火粉料、粘接剂、助熔剂等粉料,经过造粒、干燥、筛分、烧结制成。具有耐火度高,球形度高等优点。主要应用于覆膜砂,其他应用较少。结果表明,通过烧结陶粒砂实际应用于三乙胺冷芯盒工艺制芯发现,烧结陶粒砂表面有孔洞,造成冷芯盒强度低。烧结陶粒砂在覆膜砂中应用,具有强度高,膨胀率低的优势。     

湿度对壳型覆膜砂热裂倾向的影响

研究了环境湿度对壳型覆膜砂热开裂倾向及常温抗拉强度的影响，指出应结合生产实际对覆膜砂所生产的铸型、型芯适当存放，以减轻铸造缺陷，提高经济效益。环境湿度对覆膜砂铸型（芯）性能的影响是通过粘接桥界面上水分的积聚而起作用的。     

选择性激光烧结铸造覆膜砂的实验研究

通过对铸造用覆膜砂烧结实验,激光功率、扫描速度、预热温度、光斑直径工艺参数对烧结试样成型精度和烧结质量的影响,总结出了制件尺寸随各工艺参数变化的趋势。并提出烧结制件后处理的合理温度范围。     

选区激光烧结覆膜砂的保温实验研究

采用选区激光烧结技术制备的覆膜砂模型内部存在一些未完全固化的酚醛树脂,导致成型覆膜砂的力学性能达不到预期效果。为了改善覆膜砂制件的性能,对选区激光烧结成型的覆膜砂试样进行了适当的二次处理。结果发现,在250℃保温30 min处理后,覆膜砂试样的拉伸强度提升明显,试样的拉伸强度达到3.86 MPa。     

铸造烧结陶粒砂在制芯中的应用

介绍了烧结陶粒砂主要性能特点、成分和耐火度,及烧结陶粒砂和宝珠砂主要性能指标。阐述了铸造烧结陶粒砂在冷芯盒和覆膜砂制芯工艺的开发背景和应用情况。     

树脂砂用主要原材料性能及检测方法（6）

3 各树脂砂工艺用附加剂 3.1 覆膜砂用附加剂 （1）壳型（芯）用覆膜砂中通常加入硬脂酸钙一类润滑剂物质,一直沿用至今.它的加入既有利于改善或防止覆膜砂储存过程中结块,增加覆膜砂的流动性,使制出的壳型（芯）表面致密,并提高其强度;也有利于改善壳型（芯）的起模性（起润滑剂作用）.硬脂酸钙的加入量为树脂质量的2.5％～5.0％时,强度几乎增加一倍,而且显著增加了硬化后壳型（芯）的密实度.另外,采用质量好的硬脂酸钙还有利于减少脱壳倾向.     

选择性激光烧结覆膜砂芯成形工艺的研究

选择性激光烧结覆膜砂芯的成形过程分烧结和后固化两步。通过测量烧结件的弯曲强度可以得出:最适合烧结的覆膜砂的固化剂用量为15%、树脂用量为3.5%,由PF-1350型树脂所构成;激光功率为40W时为最佳烧结功率。将弯曲试样经过后固化,测其弯曲强度的极大值确定最佳固化温度为180℃,最佳固化时间为10min。并且通过试验得出砂件经过后固化后,强度提高了10倍左右。     

壳型（芯）用覆膜砂脱壳缺陷的防止

通过对壳型（芯）的成型试验和机理分析,提出了覆膜砂脱壳缺陷产生的主要原因是,在壳型（芯）成型过程中,覆膜砂的软化状态区厚度大,受重力及其它外力作用,软化区覆膜砂克服熔融树脂的粘结力而脱离固体型壳。降低覆膜砂脱壳缺陷的关键是减薄软化层的厚度,为此应选用具有较高熔点、较快结壳速度和较大热态强度与常温强度比值的覆膜砂。     

Design of multistep aging treatments of 2099 (C458) Al-Li alloy

Multistep artificial aging treatments coupled with various natural aging times for aluminum lithium 2099 alloy (previously called C458) are discussed to obtain mechanical tensile properties in the T6 condition that match those in the T861 condition, having a yield strength in the range of 414–490 MPa (60–71 ksi), an ultimate strength in the range of 496–538 MPa (72–78 ksi), and 10–13% elongation. Yield and ultimate tensile strengths from 90–100% of the strength of the as-received material (in the T861 condition) were obtained. The highest tensile strengths were consistently obtained with two-step, low-to-high temperature artificial aging treatments consisting of a first step at 120 °C (248 °F) for 12–24 h followed by a second step between 165 and 180 °C (329–356 °F) for 48–100 h. These T6-type heat treatments produced average yield and ultimate strengths in the longitudinal direction in the range of 428–472 MPa (62.1–68.5 ksi) and 487–523 MPa (70.6–75.9 ksi), respectively, as well as lower yield strength anisotropy when compared with the as-received material in the T861 condition.     

Experimental investigation on high strength steel (HSS) tailor-welded blanks (TWBs)

This paper aims to investigate mechanical characteristics of the new tailor-welded blank (TWB) components made of high strength steel (HSS). A series of HSS-TWB thin plates with different orientations of weld line are studied through three-point bending tests to evaluate the effects of different design parameters, such as weld line locations and material combinations, on the deformation behaviors. The experimental results exhibit good repeatability of tests. And the relative shift phenomenon between indenter and specimen is observed and analyzed for the TWB steel sheets with different weld line orientations at parallel and 45° to the bending moment, respectively. The results from the experiment include the force versus displacement curves and some detailed photographical images throughout the loading process. It is found that the discrepancy of different combinations is quite noteworthy. In this paper, the peak force, absorbed energy and bending strength are presented to evaluate the mechanical characteristics of HSS-TWB thin plates with different weld line orientations and material combinations. The comparison demonstrates that the TWB structures with the weld orientation at 45° angle to the bending moment have the greatest advantages of different TWB steel sheets.     

采用氢化-脱氢（HDH）钛粉和氢化钛粉制备MIMTi-6Al-4V合金

以HDH钛粉制备MIM Ti-6Al-4V合金的过程为参照,对使用氢化钛粉为原料制备P/M模压钛合金以及MIM钛合金的工艺过程进行了探索.使用HDH钛粉制备的MIM Ti-6Al-4V合金抗拉强度为819 MPa,拉伸样延伸率为7%;使用氢化钛粉制备的P/M模压Ti-6Al-4V合金拉伸样抗拉性能高于850 MPa;使用氢化钛粉为原料制备MIM Ti-6Al-4V合金,顺利实现了脱氢-脱脂过程.     

Numerical simulation of temperature and strength distributions of mold(core) on heating

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Pt(100)/ZrO2(100)界面性质的第一性原理

采用密度泛函理论的平面波赝势法,分别研究在ZrO2(100)面上以氧为键桥和以锆为键桥的Pt(100)/ZrO2(100)界面模型的结合能、电子结构以及等电荷差分密度分布图。结果发现:在以氧为键桥的Pt(100)/ZrO2(100)-bridgeO界面结合能为1.978J/m2,而以锆为键桥的Pt(100)/ZrO2(100)-bridgeZr界面结合能为10.035J/m2,前者的界面结合能低于后者的界面结合能,即以锆为键桥的ZrO2(100)更容易与Pt(100)面结合。通过电子结构和等电荷差分密度分布图分析可知,以氧为键桥的Pt(100)/ZrO2(100)-bridgeO时,主要是锆氧之间存在电子转移,而以锆为键桥的Pt(100)/ZrO2(100)-bridgeZr时,不仅锆氧之间、而且铂锆之间也存在电子转移,铂锆之间主要是锆的4d电子轨道和铂的5d以及部分6s、5p电子轨道上的电子发生了转移并且成键结合,这说明在铂基材料中以锆为键桥的界面结合能有效提高铂基材料的强度。     

Ultrasonic weld properties of heterogeneous polymers: Polylactide and poly (methyl methacrylate)

This paper aims to investigate the effects of welding conditions and the correlation between welding strengths and interfaces structures on the weld between polylactide (PLA) and poly (methyl methacrylate) (PMMA). Using our proposed ultrasonic weld (USW) method, PLA and PMMA composites (PLA/PMMA) are valid to employ as interposed sheet (IPS) experimentally. There are optimum welding times and welding presses depending on the peak welding strengths. The maximum welding strength can reach as high as 90% of the tensile strength of the matrix PLA, while the welding time is 4 s and welding press is 0.6 MPa. But excessive welding presses are deleterious to the weld, and it can also bring IPS destroying during the weld work.     

Investigating on casting mold (or core) making with coated sand by the selected laser sintering

1 .Introduction Based on the parameters and cross-section's information from a CAD model, the selected laser sintering (SLS) uses a laser beam to sinter selectively powdered solid materials (plastic, wax, ceramic, metal, etc.), and the solidified material is built up layer by layer to formthepart needed} As there are still some problems in material and technology, it is difficulty to sinter or produce directly     

Stability of Retained Austenite Through a Combined Intercritical Annealing and Quenching and Partitioning(IAQP) Treatment

Intercritical annealing(IA) at various temperatures followed by quenching and partitioning(IAQP) treatments was conducted on a cold-rolled Fe-0.2C-1.42Si-l.87Mn(wt%) sheet steel.Optimized microstructure and enhanced mechanical properties were achieved through appropriate adjustment of IA temperatures.The steel which was annealed at1,033 K for 600 s,then quenched to 573 K and partitioned at 693 K for 20 min,designated as 1033 QP steel,exhibits maximum 16.3 vol% retained austenite(RA) with good mechanical properties(ultimate tensile strength 886 MPa and total elongation 27%).It was found that the thermal and mechanical stabilities of RA are mainly influenced by the combined effect of its average carbon content and amount of adjacent martensite.Furthermore,the transformation-induced plasticity effect increased the peak n-values observed at the second stage of the work hardening of IAQP steels.     

Ti（C,N）基金属陶瓷相界面层微晶结构的形成

获得了Ｔｉ（Ｃ，Ｎ）基金属陶瓷微晶化界面过渡层的条件是碳化物相的微晶化及冷却过程中的成分过冷。相界面层微晶结构的形成使金属陶瓷的韧性得到提高，性能稳定性是到改善。     

Zr含量对Al3(ZrxEr1-x)相价电子结构与合金性能的影响

用固体与分子经验电子理论(EET)计算研究了微量元素Er,Zr添加到铝合金中产生的Al3Er和Al(ZrIxEr1-x)相的价电子结构,探讨了不同Zr含量对Al3(ZrxFr1-x)相各电子结构参数的影响.计算结果表明:随着Zr原子含量的增加,表征强度性能的最强键上的共价电子对数na和相结构形成因子S会减小,这说明合金...