Simulation of polycrystalline aluminum tensile test with crystal plasticity finite element method

The crystal plasticity was implemented in the finite element method（FEM） software ABAQUS through the user subroutine UMAT. By means of discretizing the space at the grain level with the Voronoi diagram method, a polycrystal model was built and used in the FEM analysis. The initial orientation of each grain was generated based on the orientation distribution function（ODF）. The developed model was successfully applied in simulation of polycrystalline aluminium samples deformed by the tensile tests. The theoretical strain--stress relation was in good agreement with the experimental result. The simulation results show that the grain size has significant effect on the deformation behavior. The initial plastic deformation usually occurs at grain boundaries, and multiple slip often results in an enhanced local hardening at grain boundaries.     

The Friction and Wear Properties of CrN, Graphit-iC and Dymon-iC Coatings in Air and under Oil-lubrication.

NITRIDE COATINGS have always been the popularchoice for increasing the wear lifetime for industrialcomponents.TiN is the most widely accepted butrecently CrN has been gaining more interest due itsthermal stability and good performance in corrosiveenvironments.Knowledge of the tribologicalperformance of CrN coatings in dry and lubricatedconditions is still quite limited[1,2].Many authorshave studied the properties of diamond like carbon(DLC)films and how they perform in dry conditions[…     

数值模拟铸件充型过程中的液/固两相流动

铸造过程中熔融金属内的固体渣粒的运动轨迹是非常重要的。文中给出了粒子传输轨迹的数学模型,该数学模型采用显示法来确定粒子的位置。模拟研究结果与用其它数学模型的模拟结果比较,吻合良好。该模型可用于固体粒子位置的确定,并应用到SUTCAST软件中。     

The Inventory for Chinese LFC in 2006

1. Introduction Lost Foam Casting has been introduced into China for two decades, and it is getting more popularity in foundry industry.In China there are two associations responsible for the LFC industry and academic exchanges: Chinese Lost Foam Casting Society (CLFCS) and Chinese Association of Full Mold Casting.     

Structure and Properties Characterization of Ceramic Coatings Produced on Steel Using a Combined Technique

STEEL is the most widely used material in engineering,but unfortunately,steel exhibits poor wear resistanceand obvious contact corrosion.For decades,researchersprepared coatings on steel to improve its properties;ceramic is one of these coatings.To obtain ceramiccoatings on steel,many researchers use techniques suchas plasma spraying,laser cladding,etc.,but some ofthem are too expensive,some of them have a deep heataffected zone in the substrate,and some of them cannot bond well with the subs…     

OBSERVATION ON SPUTTERING SURFACE OF ALLOYS IN GLOW DISCHARGE

Glow discharge cathodic sputtering of alloys containing second phase precipitates or injectedoxide particles has been observed with energy dispersive X-ray spectrometer and scanningelectron microprobe.It was shown that the formation of cones during the sputtering in thesealloys is due to masking of the matrix by glow sputtering second phase precipitates or oxideparticles.At steady state,the density of cottes were found to be a function of the densities pre-cipitates or oxide particles in bulk alloy.In addition to the changes of local sputtering rate,theelectrostatic effect may play a role on the formation fo cones.     

ON THE COMPOSITION UNIFORMITY AND SHAPE COEFFICIENT OF MOLTEN POOL BY LASER ALLOYING

The effect of the laser processing parameters on the composition uniformity and shapecoefficient of fusion zone with laser surface alloyed Cr plated on medium carbon low alloysteel has been studied.It was found that the composition uniformity depends on the shapecoefficient of fusion zone,and the later is a function of both power density and interactiontime.If the power density is fixed to a certain value,the shape coefficient is directly,propor-tional to the interaction time.A completely,uniform molten pool can be obtained,when theshape coefficient is between 1.6 and 3.0.     

MICROSTRUCTURE AND MECHANICAL BEHAVIOUR OF Al-Li-Zr AND Al-Li-Cu-Mg-Zr ALLOYS

The aging response,tensile and impact properties of two kinds of Al-Li based alloys havebeen studied.The microstructure,deformation as well as fracture behaviour in the alloys wereobserved with SEM and TEM.It was found that the mechanisms of deformation and fracturefor different heat-treated alloys with the same chemical composition are quite different.Thecauses leading to the drop of ductility,toughness as well as anisotropy in peak-aged alloyshave been analysed.Finally,possible methods to improve the ductility and toughness of the al-loys have been discussed.     

EFFECT OF AGING ON HYDROGEN EMBRITTLEMENT SUSCEPTIBILITY OF STEEL Cr21Ni6Mn9N

Effects of 650℃ aging for 1—1000 h on structure and hydrogen embrittlement susceptibility(HES)of steel Cr21Ni6Mn9N have been investigated.The results show that M_(23)C_6 typecarbide precipitates at grain boundaries and Cr-depletive region appears beside them duringaging.The precipitates grow and connect each other as the aging time prolongs.Meanwhile,the degree of Cr-depletion aggravates first and then recovers gradually while the aging time isvery long,i.e.,1000 h.The HES of the steel increases with increasing aging time but does notreduce with the recovery of Cr content at the Cr-depletive region.That implies that the ex-isting of carbides at grain boundaries might be the main reason which promotes the HES ofsteel during aging.     

THERMODYNAMICS OF BAINITIC TRANSFORMATION IN Cu-24 at.-% Al ALLOY

Two driving forces △G~((β_1)+α')and △G~(β_1→β_2+α)for the bainitic transformation have been calcu-lated for Cu-24 at.-% Al alloy.Results reveal △G~(β_1→α')>0 within the transformation tem-perature range 600—750 K.Therefore,the bainitic transformation cannot be initiated by theβ_1→α' shearing mechanism.On the other hand,the driving force △G~(β_1→β_2+α)to produce 5% ofthe α becomes negative only when the composition of the α satisfiesx_(Al)~α≤0.204 at 700 K or x_(Al)~α=0.209 at 750 K.So the bainitic transformation can only proceedby β_1→β_2+α diffusional reaction with different diffusion amount at different temperatures.