Jie Chen
,
Chong-Gao Bao
,
Yong Wang
,
Jin-Ling Liu
,
Challapalli Suryanarayana
金属学报(英文版)
doi:10.1007/s40195-015-0333-6
Magnesium matrix composites reinforced with AlN particles were fabricated by the powder metallurgy technique. The evolution of lattice constants and solid solubility levels of Al in α-Mg and the microstructure of Mg-Al/AlN composites were investigated in the present study. The results showed that the solid solubility of Al in α-Mg reached a relatively high level by the P/M process with a long time of milling. X-ray diffraction showed that the peaks of Mg phase clearly shifted to higher angles. The lattice constants and cell volume decreased significantly compared with those of standard Mg due to a significant amount of Al incorporated into α-Mg in the form of substitutional solid solution. The degree of lattice deformation decreased at a low sintering temperature and increased at higher sintering temperatures due to the presence of AlN. Microstructural characterization of the composites revealed a necklace distribution of AlN particles in the Mg matrix. Heat treatment led to precipitation of Mg17Al12 from the supersaturated α-Mg solid solution. The precipitate exhibited granular and lath-shaped morphologies in Mg matrix and flocculent precipitation around AlN particles.
关键词:
Metal matrix composite
,
AlN particle
,
Microstructure
,
Lattice parameter
,
Powder metallurgy
,
Solid solubility
Jianzhong WANG
金属学报(英文版)
doi:10.1016/S1006-7191(08)60122-2
A new method for producing higher density PM parts, high velocity compaction (HVC), was presented in the paper. Using water atomized pure iron powder without lubricant admixed as the staring material, ring samples were compacted by the technique. Scanning electron microscopy (SEM) and a computer controlled universal testing machine were used to investigate the morphologies and the mechanical properties of samples, respectively. The relationships among the impact velocity, the green density, the sintered density, the bending strength and the tensile strength were discussed. The results show that with increasing impact velocity, the green density and the bending strength increase gradually, so the sintered density does. In addition, the tensile strength of sintered material is improved continuously with the sintered density enhancing. In the study, the sintered density of 7.545~g/cm3 and the tensile strength of 190~MPa are achieved at the optimal impact velocity of 9.8 m/s.
关键词:
Powder metallurgy
,
high velocity compaction
,
green properties
,
stress wave
,
bending strength
Mustafa Boz
,
Adem Kurt
,
null
,
null
材料科学技术（英文）
Iron powders were mixed with graphite powders by 1~15 wt pct to produce block samples using powder metallurgy technique. The powders were blended in a three dimensional blender for 20 min and compacted in a die under 500 MPa by using a one directional press. Sinterability and mechanical properties of the samples with different carbon content were investigated. Sintering process was carried out on a belt furnace with flame curtain in dissociated ammonia atmosphere. Block samples produced were suitable for ASTM B-312 transverse rupture strength test apparatus and were tested with 0.050 kN/s velocity in a press under 100 g load. It was found that graphite amount up to 2 wt pct increased the contact area of particles and acted as a lubricant to affect the sintering behaviour positively. The results indicated that the samples containing up to 5 wt pct showed good sintering behaviour and also good hardness due to an increase in pearlite amount. However, the samples containing higher amount of graphite (more than 5 wt pct) affected the sintering behaviour negatively due to the settlement of free graphite around the Fe powders, which resulted in a decrease in the hardness and transverse rupture strength.
关键词:
Powder metallurgy
,
null
,
null
,
null
,
null
Liqing CHEN
,
Naoyuki Kanetake
材料科学技术（英文）
Ingot metallurgy (IM) aluminum has long been the subject and attracted the attention of many metallurgists and textural researchers of materials. Due to the introduction of large amounts of ex situ interfaces, however, the textures in powder metallurgy (PM) processed aluminum has been rarely reported. In this article, a pure aluminum plate was prepared $via$ PM route. The starting billet was first produced with uni-axially cold compaction and flat hot-extrusion and then followed by cold rolling processes. The hot-extruded and cold rolling deformation textures of the pure PM aluminum at 50%, 80% and 90% cold rolling reductions were studied by orientation distribution functions (ODFs) analysis. The finite element polycrystal model (FEPM) was finally utilized to simulate the cold rolling textural evolution at various stages of cold rolling. In FEPM simulation, the initial hot-extruded textures were taken into account as inputs. The results showed that typical β-fiber texture formed in pure PM aluminum with the cold rolling reduction increased till 80%, and there was not much change after excessive cold rolling deformation. Homogeneous slip is not the only deformation mode in PM processed pure aluminum plate at over 80% cold rolling reduction. The experimental results were qualitatively in good agreement with the simulated ones.
关键词:
Texture
,
null
,
null
,
null
,
null
Montasser DEWIDAR
,
H.Fouad MOHAMED
材料科学技术（英文）
Titanium and its alloys are currently considered as one of the most important metallic materials used in the biomedical applications, due to their excellent mechanical properties and superior biocompatibility. In the present study, a new effective method for fabricating high porosity titanium alloy scaffolds was developed. Porous Ti-6Al-4V scaffolds are successfully fabricated with porosities ranging from 30% to 70% using space-holder and powder sintering technique. Based on its acceptable properties, spherical carbamide particles with different diameters (0.56, 0.8, and 1 mm) were used as the space-holder material in the present investigation. The Ti-6Al-4V scaffolds porosity is characterized by using scanning electron microscopy. The results show that the scaffolds spherical-shaped pores are depending on the shape, size and distribution of the space-holder particles. This investigation shows that the present new manufacturing technique is promising to fabricate a controlled high porosity and high purity Ti-6Al-4V scaffolds for hard tissue replacement.
关键词:
Ti-6Al-4V
,
null
,
null
,
null
Yong LIU
,
Baiyun HUANG
,
Kechao ZHOU
,
Hongwu OUYANG
,
Yuehui HE
材料科学技术（英文）
In order to overcome the shortcomings of conventional hot pressing, a novel near net-shape technique, called radial hot pressing, for P/M parts with large height-to-diameter (H/D) ratio was introduced. Effects of processing parameters on the microstructures and density of P/M TiAl base alloy valves were studied. Results show that the radial hot pressing is an effective technique for manufacturing valves with a H/D ratio of about 10:1, and the perfect joint interface between the Mo sheet and the parts is helpful for subsequent HIPing.
关键词:
Near net-shape technique
,
null
,
null
Wenjue CHEN
,
Yueying WU
,
Jianian SHEN
材料科学技术（英文）
A sandwich structure with cladding alloyed 316L stainless steel on plain carbon steel was prepared by means of powder metallurgy (PM) processing. Electrolytic Cu and prealloyed bronze (95Cu wt pct, 5Sn wt pct) were added in different contents up to 15 % into the surface cladded 316L layers and the effect of alloying concentrations on the corrosion resistance of the 316L cladding layers was studied. The corrosion performances of the cladding samples were studied by
immersion tests and potentio-dynamic anodic polarization tests in H2SO4 and FeCl3 solutions. Both 316L and alloyed 316L surface layers with 1.0 mm depth produced by PM cladding had an effect to improve corrosion resistance in H2SO4 and FeCl3 solutions. Small Cu and bronze addition (4 %) had a positive effect in H2SO4 and FeCl3 solutions. 4 % Cu alloyed 316L surface layer produced by PM cladding showed similar anodic polarization behaviour to the 316L cladding layer in H2SO4 and FeCl3 solutions.
关键词:
Surface cladding
,
null
,
null
Zhenzhu ZHENG
,
Lin GENG
,
Honglin WANG
,
Weimin ZHOU
,
Hongyu XU
材料科学技术（英文）
In-situ 5 vol.pct TiB whiskers and TiC particulates reinforced Ti composites were fabricated by blending Ti powder and B4C particulates followed by reactive hot-pressing. The microstructure of the composites was investigated by using differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The results showed that the reactive temperature between Ti and B4C is above 570°. Two kinds of reinforcements with different shapes were formed during hot-pressing: TiB short-fiber and equiaxed TiC particles. The interfacial bonding between the reinforcements and Ti matrix is perfect. No interfacial reaction between reinforcements and Ti matrix was found.
关键词:
Ti matrix composite
,
null
,
null
毛斐
,
吴振兴
,
汤皎宁
,
王涵
,
刘正楷
,
龚晓钟
材料热处理学报
对N型Si80Ge20(P4)x及P型Si80Ge20Bx固溶体合金的化学计量比进行了研究,采用已总结出的最佳工艺条件,制备了一系列N型、P型固溶体合金,并比较了各系列样品的热电性能.结果表明,x=1.5的N型Si80Ge20(P4)x固溶体合金具备良好的热电性能,与未掺杂Si80Ge20固溶体合金相比,最高热电优值ZT为0.651,提高了3.34倍.x=1.5的P型Si80Ge20Bx固溶体合金也具备较佳的热电性能,最高热电优值(ZT)值为0.538.
关键词:
热电材料
,
Si80Ge20
,
粉末冶金
,
热电性能
