用真理铸造学生的灵魂

用真理铸造学生的灵魂李植汉，湖北省枝江市一中特级教师、政教处主任，宜昌市中学政治研究会副理事长，省德育先进工作者，市专业技术拔尖人才。１９６２年，他毕业于武汉师范学院，被分配到三峡东大门——枝江市。在这里，他从事中学政治教育，一干就是３５年。长期的教...

江苏省铸造分会召开理事换届会

江苏省铸造分会于1989年11月10日到12日在南通市召开理事会换届会。到会代表包括原三届理事与新聘任的四届理事共63人。

我们的学术活动中心

西北工业大学铸造学科(专业)学术活动中心是1984年由铸造教研室周尧和教授倡议成立、由铸造学科(专业)研究生自行组织和主持的活动形式。其主要成员是铸造学科(专业)的博士生和硕士生。由于他们所从事的学位课题牵涉面广。

《铸造缺陷及其对策》

由日本铸造工学会编写,由大连理工大学张俊善教授和尹大伟先生翻译成中文,机械工业出版社出版。通俗易懂地解说各种铸造缺陷,能够帮助现场的铸造技术人员及时判断他所遇到的缺陷属于何种类型的缺陷,找出缺陷产生的原因及解决方案,是铸造相关人员的好帮手。全书分8部分,247页,234千字。16开,精装,定价58元,特快专递邮购价:80元。

“铸造南洋文艺”：一个《南洋文艺》编辑的经验与尝试

笔者1994年主编《南洋商报》文艺副刊"南洋文艺"后,在"铸造南洋文艺"的理念推动下,积极调整副刊编辑路向,采取为马华作家塑像、推动马华文学评论、整理阶段性马华文学史和鼓励文学与时事结合等策略,张扬与促进马华本土文学的发展,让马华文学得以被"看见"。

地方学会动态

辽宁省机械工程学会铸造学组铸造机械化自动化及环境保护专业分组第一次会议,于六月十二日在旅大市召开。会议根据全国及省铸造学组七九～八○年工作要点及活动计划,讨论了本专业分组的工作要点和健全各级组织的措施,拟定了一九七九年的学术活动计划。

Effect of heat treatment on microstructures and mechanical properties of sand-cast Mg-4Y-2Nd-1Gd-0.4Zr magnesium alloy

Influence of heat treatment on the microstructures and mechanical properties of sand-cast Mg-4Y-2Nd-1Gd-0.4Zr magnesium alloy was investigated,and the tensile fracture mechanisms of the studied alloys under different conditions were also discussed.The results show that the optimum T4 and T6 heat treatment conditions for the as-cast Mg-4Y-2Nd-1Gd-0.4Zr alloy are 525°C,8 h and（525°C,8 h）＋（225°C,16 h）,respectively,with regard to the microstructure observation,DSC heating curve and mechanical properties.The hardness,yield strength,ultimate tensile strength and elongation of the Mg-4Y-2Nd-1Gd-0.4Zr alloy treated by optimum T6 heat treatment are HV91,180 MPa,297 MPa and 7.4%,respectively.Moreover,the Mg-4Y-2Nd-1Gd-0.4Zr alloys under different heat treatment conditions exhibit different tensile fracture modes.

Microstructure and mechanical properties of Mg-Gd-Y-Zr alloy cast by metal mould and lost foam casting

The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr （mass fraction, %） alloy （GW104 alloy） cast by metal mould casting （MMC） and lost foam casting （LFC） were evaluated, respectively. It is revealed that different forming modes do not influence the phase composition of as-cast alloy. In the as-cast specimens, the microstructures are similar and composed of α-Mg solid solution, eutectic compound of α-Mg＋Mg 24 （Gd, Y） 5 and cuboid-shaped Mg 5 （Gd, Y） phase; whereas the average grain size of the alloy produced by metal mould casting is smaller than that by lost foam casting. The eutectic compound of the alloy is completely dissolved after solution treatment at 525 ℃for 6 h, while the Mg 5 （Gd, Y） phase still exists after solution treatment. After peak-ageing, the lost foam cast alloy exhibits the maximum ultimate tensile strength of 285 MPa, and metal mould cast specimen 325 MPa at room temperature, while the tensile yield strengths of them are comparable. It can be concluded that GW104 alloy cast by lost foam casting possesses similar microstructure and evidently lower mechanical strength compared with metal mould cast alloy, due to slow solidification rate and proneness to form shrinkage porosities during lost foam casting process.

Low cycle fatigue behavior of T4-treated Al-Zn-Mg-Cu alloys prepared by squeeze casting and gravity die casting

Gravity die casting(GC) and squeeze casting(SC) T4-treated Al-7.0Zn-2.5Mg-2.1Cu alloys were employed to investigate the microstructures,mechanical properties and low cycle fatigue(LCF) behavior.The results show that mechanical properties of SC specimens are significantly better than those of GC specimens due to less cast defects and smaller secondary dendrite arm spacing(SDAS).Excellent fatigue properties are obtained for the SC alloy compared with the GC alloy.GC and SC alloys both exhibit cyclic stabilization at low total strain amplitudes(less than 0.4%) and cyclic hardening at higher total strain amplitudes.The degree of cyclic hardening of SC samples is greater than that of GC samples.Fatigue cracks of GC samples dominantly initiate from shrinkage porosities and are easy to propagate along them,while the crack initiation sites for SC samples are slip bands,eutectic phases and inclusions at or near the free surface.

Microstructure evolution and tensile mechanical properties of thixoformed AZ61 magnesium alloy prepared by squeeze casting

A novel process that combines squeeze casting with partial remelting to obtain AZ61 magnesium alloy with semi-solid microstructures was proposed. In this route, the squeeze casting was used to predeform the magnesium alloy billets to obtain small dendritic structures. During subsequent partial remelting, small dendritic structures transform into globular grains surrounded by liquid films. The results show that the squeeze casting AZ61 alloy after partial remelting produces more ideal, finer semi-solid microstructure compared with as-cast AZ61 alloy treated by the same isothermal holding conditions. Moreover, the mechanical properties of the thixoformed AZ61 alloy prepared by squeeze casting plus partial remelting are better than those of the thixoformed alloy prepared by conventional casting plus partial remelting.

Microstructures and properties of A356-10%SiC particle composite castings at different solidification pressures

A356-based metal matrix composites with 10% SiC particles of 10 rtm were fabricated by stir casting and direct squeeze casting process under applied pressures of 0.1 （gravity）, 25, 50 and 75 MPa. The microstructures and mechanical properties of the as-cast and T6 heat-treated castings were investigated. The results show that as the applied pressures increase, the casting defects as particle-porosity clusters reduce and the incorporation between the particles and matrix can be improved. The tensile strength, hardness, and coefficients of thermal expansion （CTE） increase with the increase of the pressures. Compared with the as-cast composite castings, the tensile strength and hardness of the heat-treated casting are improved whereas CTEs tend to decrease in T6-treated condition. For the gravity cast composites, there are some particle-porosity clusters on the fracture surface, and the clusters are hardly detected on the fracture surface of the samples solidified at the external pressures. Different fracture behaviors are found between the composites solidified at the gravity and imposed pressures.

Optimization of AZ80 magnesium alloy squeeze cast process parameters using morphological matrix

The squeeze cast process parameters of AZ80 magnesium alloy were optimized by morphological matrix. Experiments were conducted by varying squeeze pressure, die pre-heat temperature and pressure duration using L9（33） orthogonal array of Taguchi method. In Taguchi method, a 3-level orthogonal array was used to determine the signal/noise ratio. Analysis of variance was used to determine the most significant process parameters affecting the mechanical properties. Mechanical properties such as ultimate tensile strength, elongation and hardness of the components were ascertained using multi variable linear regression analysis. Optimal squeeze cast process parameters were obtained.

Smoothed particle hydrodynamics modeling and simulation of foundry filling process

A numerical model of foundry filling process was established based on the smoothed particle hydrodynamics（SPH）method.To mimic the constraints that the solid mold prescribes on the filling fluid,a composite treatment to the solid boundaries is elaborately designed.On solid boundary surfaces,boundary particles were set,which exert Lennard-Jones force on approaching fluid particles;inside the solid mold,ghost particles were arranged to complete the compact domain of near-boundary fluid particles.Water analog experiments were conducted in parallel with the model simulations.Very good agreement between experimental and simulation results demonstrates the success of model development.

Influence of pouring temperature on solidification behavior, microstructure and mechanical properties of sand-cast Mg-10Gd-3Y-0.4Zr alloy

Influence of the pouring temperature ranging from 680 to 780 ℃ on the solidification behavior, the microstructure and mechanical properties of the sand-cast Mg-10Gd-3Y-0.4Zr alloy was investigated. It was found that the nucleation undercooling of the a-Mg phase increased from 2.3 to 6.3 ℃. The average a-Mg grain size increased from 44 to 71 μm, but then decreased to 46 μm. The morphology of the eutectic compound transformed from a continuous network into a discontinuous state and then subsequently into an island-like block. The volume fraction of β-Mg_24RE_5 phase increased and its morphology transformed from particle into rod-like. The increase in pouring temperature increased the solute concentration. YS increased from 138 to 151 MPa, and UTS increased from 186 to 197 MPa. The alloy poured at 750 ℃ had optimal combining strength and ductility. The fracture surface mode transformed from quasi-cleavage crack into transgranular fracture, all plus the dimple-like fracture, with the micro-porosity and the re-oxidation inclusion as major defects. The average a-Mg grain size played a main role in the YS of sand-cast Mg-10Gd-3Y-0.4Zr alloy, besides other factors, i.e. micro-porosity, morphology of eutectic compounds, re-oxidation inclusion and solute concentration.

Fabrication and characterization of stir casting AA6061-31%B_4C composite

A sophisticated stir casting route to fabricate large scale AA6061-31%B4C composite was developed. Key process parameters were studied, microstructure and mechanical properties of the composite were investigated. The results indicated that vacuum stirring/casting, B4C/Mg feeding and ingots cooling were essential to the successful fabrication of AA6061-31%B4C composite. Chemical erosion examination verified the designed B4 C content; X-ray fluorescence spectrometer（XFS） showed the chemical composition of Mg and Si in the matrix conformed to industry standards; scanning electronic microscope（SEM） and X-ray diffraction（XRD） revealed that B4 C particles were evenly distributed in the composites with well dispersed Mg2Si precipitates. Tensile testing results showed that the AA6061-31%B4C composite had a tensile strength of 340 MPa, improved by 112.5% compared with AA1100-31%B4C composite, which is attributed to the enhanced strength of the matrix alloy.

Effect of applied pressure on microstructure and mechanical properties of Mg-Zn-Y quasicrystal-reinforced AZ91D magnesium matrix composites prepared by squeeze casting

The Mg-Zn-Y quasicrystal-reinforced AZ91 D magnesium matrix composites were prepared by squeeze casting process. The effects of applied pressure on microstructure and mechanical properties of the composites were investigated. The results show that squeeze casting process is an effective method to refine the grain. The composites are mainly composed of α-Mg, β-Mg17Al12 and Mg3Zn6Y icosahedral quasicrystal phase（I-phase）. With the increase of applied pressure, the contents of β-Mg17Al12 phase and Mg3Zn6 Y quasicrystal particles increase, further matrix grain refinement occurs and coarse dendritic α-Mg transforms into equiaxed grain structure. The composite exhibits the maximum ultimate tensile strength and elongation of 194.3 MPa and 9.2% respectively when the applied pressure is 100 MPa, and a lot of dimples appear on the tensile fractography. Strengthening mechanisms of quasicrystal-reinforced AZ91 D magnesium matrix composites are chiefly fine-grain strengthening and quasicrystal particles strengthening.

Microstructure and mechanical properties of overcast aluminum joints

The aluminum joints were prepared by overcasting liquid aluminum A356 onto 6101 aluminum extrusion bars. The microstructure, element distribution, hardness and tensile strength of the joint interface area were investigated, the mechanism of interface formation and fracture behavior were analyzed. The results show that good metallurgical bonding was formed in the joints by electro-plating the solid 6101 aluminum alloy with a layer of zinc coating and carefully controlling the overcasting process. There is a transition zone between the two bonded aluminum alloys, and the fine equiaxed grained structure in the transition zone is due to the high undercooling during solidification. The tensile strength of the joint interface is higher than that of the as-cast A356 aluminum alloy(about 145 MPa) and the final fracture is always located in the as-cast A356 material.

Effect of Nb addition on microstructure,mechanical properties and castability of β-type Ti-Mo alloys

To develop novel β-type biomedical titanium alloys,a series of Ti-15Mo-xNb alloys（x=0,5,10 and 15,mass fraction in%） were designed and prepared by using vacuum arc melting method.The present study focused on the effect of Nb addition on the microstructure,mechanical properties and castability of Ti-15 Mo alloy.Phase analysis and microstructure observation show that all the alloys consist of single β phase and the equiaxed β grain is refined with increasing Nb content.These β-type Ti-15Mo-xNb alloys exhibit good plasticity and rather low compression elastic modulus（in the range of 18.388-19.365 GPa）.After Nb addition,the compression yield strength of the alloys increases.With increasing Nb content,the micro-hardness of the alloys decreases.The alloys exhibit obvious fibrous strip microstructure after cold compression deformation.The castability test shows that the castability of the alloys after Nb addition decreases and that of the Ti-15 Mo alloy is the highest（92.01%）.

INVESTIGATION ON MECHANICAL PROPERTIES OF ZN-AL/SIC PARTICULATE COMPOSITES

In order to improve the properties of ZA 27 and ZA4-3 zinc alloys and broaden their application ranges,SiC particlj1Ale composites, prepared by means of rheological casting technology, are investigated individually on their rT..t'llanical properties. The results of ne-cural strength, impact strensttl, compressive strength, hardness values and wear rate of the composites show that the addition of SiCp, leads to the increase of the compressive strength and hardness values at both room and higher temperature, and wear resistance of the materials, accompanying with the slight decrease of the fie-cural strength and sharp reduction of the impacttoughness. The factors affecting the mechanical properties of the composites are discussed in the paper.