Microstructure Development during Extrusion of Mechanically Alloyed Powder

ＭｉｃｒｏｓｔｒｕｃｔｕｒｅＤｅｖｅｌｏｐｍｅｎｔｄｕｒｉｎｇＥｘｔｒｕｓｉｏｎｏｆＭｅｃｈａｎｉｃａｌｌｙＡｌｌｏｙｅｄＰｏｗｄｅｒＳｈａＷｅｉ（沙维）（ＤｅｐａｒｔｍｅｎｔｏｆＣｉｖｉｌＥｎｇｉｎｅｅｒｉｎｇ，ＴｈｅＱｕｅｅｎ’ｓＵｎｉｖｅｒｓｉ...     

Diffusion Brazing of Mechanically Alloyed Oxide Dispersion Strengthened Materials

ＤｉｆｆｕｓｉｏｎＢｒａｚｉｎｇｏｆＭｅｃｈａｎｉｃａｌｌｙＡｌｌｏｙｅｄＯｘｉｄｅＤｉｓｐｅｒｓｉｏｎＳｔｒｅｎｇｔｈｅｎｅｄＭａｔｅｒｉａｌｓＳｈａＷｅｉ（沙维）（ＤｅｐａｒｔｍｅｎｔｏｆＣｉｖｉｌＥｎｇｉｎｅｅｒｉｎｇ，ＴｈｅＱｕｅｅｎ′ｓＵｎ...     

Characterisation of a Mechanically Alloyed Oxide Dispersion Strengthened Niekel－base Superalloy

ＣｈａｒａｃｔｅｒｉｓａｔｉｏｎｏｆａＭｅｃｈａｎｉｃａｌｌｙＡｌｌｏｙｅｄＯｘｉｄｅＤｉｓｐｅｒｓｉｏｎＳｔｒｅｎｇｔｈｅｎｅｄＮｉｅｋｅｌ－ｂａｓｅＳｕｐｅｒａｌｌｏｙＳｈａＷｅｉ（沙维）ＤｅｐｅｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａ...     

Influence of Process Variables on the Structure of Mechanically Alloyed Ti_3Al-base Intermetallics

During mechanical alloying variables such as the type of mill,milling intensity,milling time,milling at-mosphere and ball-to-powder weight ratio(BPR)affect the morphology and constitution of the product.The effect of milling time,milling atmosphere and BPR on the nature of the product formed in mechanical-ly alloyed pure Ti and blended elemental binary Ti-Al,and ternary Ti-AI-Nb alloy powders was described.Mechanical alloying of pure titanium results,after long milling times,in the formation of an fcc phase.Inthe binary alloy,a solid solution of aluminum in titanium,an amorphous phase,and a fcc phase form withincreasing milling time.The fcc phase,which is probably a result of TiN formation,occurs more rapidly inair or nitrogen than in an inert atmosphere.Formation of the B2 phase in the ternary alloys depends bothon alloy composition and the milling atmosphere,with 100％ formation in all atmospheres in Ti-25Al-25Nbbut not in Ti-24Al-11Nb,and an inert atmosphere favoring formation.The times required for the formationof the different phases decrease as the BPR increases;but their sequence is unaffected.Based on this infor-mation,“milling maps”which describe phase formation as a function of the BPR and milling time are con-structed.Contamination from the milling balls increased as the BPR was increased.     

Microstructure Evolution of Intermetallics Produced by Laser Powder Deposition

NiAl intermetallic alloys are potential high temperaturestructural materials in aeronautical and astronauticalindustries[1].However,the poor ductility andtoughness at room temperature severely restrict theirengineering applications[2,3].It is important todevelop new technology to product intermetallicmaterials for the improvement of the comprehensiveproperties and the workability.Laser powder depositionhas been used to synthesize many new materials.Furthermore,if incorporated with rapid proto…     

Microstructure evolution of Cu-Pb monotectic alloys during directional solidification

1 Introduction Monotectic alloy is an important class of alloy whose binary phase diagram has a miscibility gap, in which the original single liquid will decompose into two distinct immiscible liquids within a few seconds. In the normal gravity field, a …     

Microstructure evolution of nanostructured Ni3Al during annealing

A nanocrystalline layer was produced on the surface of Ni3Al intermetallic by means of surface mechanical attrition treatment. The surface nanocrystallites were annealed at 250-750 ℃ for 30 min. Microstructure evolution of nanocrystallites during annealing was studied by X-ray diffraction （XRD） and transmission electronic microscope （TEM）. The experimental results show that long-rang order recovers rapidly when annealing temperature is below 250℃ and changes slowly at 350-550 ℃, and then it increases rapidly at 750℃. The grain size of nanocrystallites of Ni3Al keeps stable and crystal defects recover when they are annealed below 550℃. The grains grow normally in low temperature annealing and abnormal growth occurs at 750℃.     

Relation between Development of Microstructure and Magnetic Properties of Sintered NdDyFeB Magnets

ＲｅｌａｔｉｏｎｂｅｔｗｅｅｎＤｅｖｅｌｏｐｍｅｎｔｏｆＭｉｃｒｏｓｔｒｕｃｔｕｒｅａｎｄＭａｇｎｅｔｉｃＰｒｏｐｅｒｔｉｅｓｏｆＳｉｎｔｅｒｅｄＮｄＤｙＦｅＢＭａｇｎｅｔｓＴａｎｇＷｅｉ；ＦｕＨｅｎｇｚｈｉ；ＺｏｕＧｕａｎｇｒｏｎｇ；ＳｈｉＺｈｅｎ...     

Phase Stability in Mechanically Alloyed Mg–Ni System Studied by Experiments and Thermodynamic Calculations

In this study, microstructural evolution of Mg–Ni alloy during mechanical alloying(MA) was investigated.Also, a thermodynamic approach was utilized to predict the most stable phases formed in Mg–Ni alloy after MA. The phase composition and microstructural properties of Mg–Ni alloy were assessed by X-ray diffractometry, high-resolution field emission scanning electron microscopy and high-resolution transmission electron microscopy. The results showed that ball milling of magnesium and nickel powder mixture for 70 h yields nanostructural Mg2Ni compound with an average grain size of ~20 nm. Thermodynamic calculations revealed that in the composition ranges of 0.0 \ XMg\ 0.03(at.%)and 0.97 \ XMg\ 1, there is no driving force for amorphous phase formation. In the composition range of 0.07 \ XMg\ 0.93, the change of Gibbs free energy for amorphous phase formation was more negative than solid solution.While for XMg= 0.66(nominal composition of Mg2Ni intermetallic phase), the change of Gibbs free energy for intermetallic phase was found to be more negative than both amorphous and solid solution phases indicating that Mg2Ni intermetallic compound is the most stable phase, in agreement with the experimental observations.     

Microstructure evolution during preparation of in-situ TiB reinforced titanium matrix composites

1　INTRODUCTIONTitaniummatrixcompositesarepromisingmate rialswhichcanbeusedextensivelyinaerospaceandautomotiveindustriesbecauseoftheirexcellentme chanicalpropertiesatroomtemperatureandelevatedtemperature[14 ] ,suchaslowdensity ,highstrength ,andcorrosion resistance .Amongthein situfabrica tionmethodsoftitaniummatrixcomposites[511] ,self propagatinghigh temperaturesynthesis (SHS )methodhasuniqueadvantage ,thatis ,thereinforce mentsarefineanddispersed .InSHS ,thereisanexothermicreactionac…     

Mechanical Property and Microstructure of Oxide Dispersion Strengthened Nickel－base Superalloy MA758

ＭｅｃｈａｎｉｃａｌＰｒｏｐｅｒｔｙａｎｄＭｉｃｒｏｓｔｒｕｃｔｕｒｅｏｆＯｘｉｄｅＤｉｓｐｅｒｓｉｏｎＳｔｒｅｎｇｔｈｅｎｅｄＮｉｃｋｅｌ－ｂａｓｅＳｕｐｅｒａｌｌｏｙＭＡ７５８ＳｈａＷｅｉ沙维（ＤｅｐａｒｔｍｅｎｔｏｆＣｉｖｉｌＥｎｇｉｎｅｅｒｉ...     

Stress－rupture Property and Microstructure of Yttria Dispersion Strengthened Alloy MA956

Ｓｔｒｅｓｓ－ｒｕｐｔｕｒｅＰｒｏｐｅｒｔｙａｎｄＭｉｃｒｏｓｔｒｕｃｔｕｒｅｏｆＹｔｔｒｉａＤｉｓｐｅｒｓｉｏｎＳｔｒｅｎｇｔｈｅｎｅｄＡｌｌｏｙＭＡ９５６ＳｈａＷｅｉ（沙维）（ＤｅｐａｒｔｍｅｎｔｏｆＣｉｖｉｌＦｎｇｉｎｅｅｒｉｎｇ，ＴｈｅＱｗｅ...     

Mechanical Property and Microstructure of Oxide Dispersion Strengthened Nickel-base Superalloy MA758

ＭｅｃｈａｎｉｃａｌＰｒｏｐｅｒｔｙａｎｄＭｉｃｒｏｓｔｒｕｃｔｕｒｅｏｆＯｘｉｄｅＤｉｓｐｅｒｓｉｏｎＳｔｒｅｎｇｔｈｅｎｅｄＮｉｃｋｅｌｂａｓｅＳｕｐｅｒａｌｏｙＭＡ７５８ＳｈａＷｅｉ（沙维）ＤｅｐａｒｔｍｅｎｔｏｆＣｉｖｉｌＥｎｇｉｎｅｅｒｉ...     

Microstructural evolution during upward and downward transient directional solidification of hypomonotectic and monotectic Al–Bi alloys

Upward directional unsteady-state solidification experiments were performed with both a hypomonotectic Al–2.0 wt% Bi alloy and a monotectic Al–3.2 wt% Bi alloy. Besides, the monotectic composition (3.2 wt% Bi) was directionally solidified under downward transient heat flow conditions, which enables the effects of melt convection on the final microstructure to be evaluated since the collective downward movement of Bi-rich particles is favored in such case. This is due to the density differences between the two coexisting liquid phases. The thermal parameters such as cooling rate, growth rate and thermal gradient were experimentally determined by data collected from cooling curves recorded along the casting length. The monotectic features observed in the Al–3.2 wt% Bi alloy castings, i.e. the interphase spacing and Bi-rich particles diameter were correlated with the growth rate and thermal gradient. The cell spacing was experimentally determined for the Al–2.0 wt% Bi alloy as a function of both the cooling rate and tip growth rate. These experimental data were compared with the main predictive cellular growth models from the literature. A comparison between upward and downward unsteady-state solidification results for the interphase spacing and Bi-rich particles diameter has also been conducted.     

粉末搭配对钨烧结坯密度及微观组织的影响

选用平均粒度为０．８～３．０μｍ的４种不同粒度钨粉进行粉末搭配研究。结果表明：当两种粉末性能相差较大时，即使其平均粒度很细，搭配粉末烧结坯［质量］密度也低，且微观组织极不均匀；当两种粉末性能相近时，搭配粉末烧结［质量］密度较高，且微观组织均匀。并用搭配粉末烧结模型对该现象进行了阐释。     

Effect of particles on microstructural evolution during cold rolling of the aluminum alloy AA3104

The effect of second-phase particles on the evolution of the deformation microstructure during cold rolling of the particle-containing aluminum alloy AA3104 has been investigated using electron channeling contrast imaging and electron backscattered diffraction (EBSD). The results show that the influence of second-phase particles on the deformation microstructure depends on the particle size. Fine dispersoids present in the microstructure have no clear effect on the grain orientation dependence of the dislocation structures formed in the strain range examined. However, large scale structural heterogeneities, in the form of deformation zones, are formed near coarse constituent particles, leading to significant local distortions of the deformed microstructure. Analysis of EBSD data shows that significant orientation gradients are found in the vicinity of the coarse particles. Within the deformation zones the largest lattice rotations occur at the tips of plate-shaped constituent particles. A symmetrical pattern of TD-rotations of alternating sign is found in the deformation zones, with the magnitude of the lattice rotations increasing with increasing strain.     

Recrystallization in Oxide Dispersion Strengthened Nickel－base Superalloy MA760

ＲｅｃｒｙｓｔａｌｌｉｚａｔｉｏｎｉｎＯｘｉｄｅＤｉｓｐｅｒｓｉｏｎＳｔｒｅｎｇｔｈｅｎｅｄＮｉｃｋｅｌ－ｂａｓｅＳｕｐｅｒａｌｌｏｙＭＡ７６０ＳｈａＷｅｉ（沙维）（ＥｅｐａｒｔｍｅｎｔｏｆＣｉｖｉｌＥｎｇｉｎｅｅｒｉｎｇ，ＴｈｅＱｕｅｅｎ＇ｓＵｎｉ...     

Effect of temperature on sintered austeno-ferritic stainless steel microstructure

The influence of temperature on microstructural changes of sintered austeno-ferritic steels has been investigated. PM stainless steels have been obtained by sintering mixtures of austenitic and ferritic stainless steel powders. Only temperature-induced phase transformation was observed in austenite, as a result of elements interdiffusion between both phases. Microstructural characterization was completed with atomic force microscopy (AFM) and micro- and nano-indentation test, it is revealed an increase in the hardness with respect to the solutionized materials.     

Sn effect on microstructure and mechanical properties of ultrafine eutectic Ti–Fe–Sn alloys

Microstructural investigations on ultrafine eutectic (Ti₆₅Fe₃₅)_100−xSn_x alloys with x = 0, 1 and 3 at.% reveal that additional Sn is effective to control formation of the micron-scale dendrites and to decrease the length-scale of lamellar spacing with enhancing macroscopic plasticity at room temperature compression. Hence, it is possible to understand the influence of the microstructural change on the plasticity of the ultrafine eutectic Ti–Fe–Sn alloys.