热处理对Fe-4Ni-1.5Cu-0.5Mo-0.5C材料组织和性能的影响

采用热模压制技术制备了高密度的Fe-4Ni-1.5Cu-0.5Mo-0.5C材料,并研究了热处理工艺对其密度、显微组织和力学性能的影响.结果表明:在850℃淬火,随保温时间的延长,抗拉强度和硬度逐渐增大,但对密度影响不大;热处理工艺为850℃保温120min时,其性能最佳,密度为7.23 g/cm3,抗拉强度为883 MPa,硬度为72.8 HRA.热处理后铁基合金组织由铁素体、珠光体、贝氏体转变为回火马氏体和部分残余奥氏体组成;断口形貌分析表明,铁基合金热处理后的断裂机理为典型的解理断裂.     

Effect of annealing processing on microstructure and properties of Ti-6Al-4V alloy by powder injection molding

Ti6Al4V alloy parts were prepared by metal injection molding. Brown parts were densified at 1 200-1 260℃ for 2-4 h in vacuum atmosphere. The as-sintered specimens were treated through Hot-Isostatic Pressure（HIP） at 960 ℃ and 140 MPa. Ti6Al4V alloy compacts were annealed at 720-760 ℃ for 1 h. The results show that binder in the parts can be removed by solvent debinding and thermal debinding process. Ti6Al4V alloy has an uniform duplex microstructure with many equiaxed a grains and a little fl grains. When the annealing temperature is higher than 800 ℃, Ti6Al4V alloy has lower mechanical properties.After solution treatment and aging, a typical martensite microstructure can be achieved.     

Mechanical properties and microstructure of Ti-6Al-4V compacts by metal injection molding

Ti-6Al-4V compacts were fabricated by metal injection molding(MIM). Influence of vacuum sintering time on mechanical properties and microstructure of the sintered compacts at 1 260 ℃ were investigated. The experimental results show that the compacts sintered at 1 260 ℃ for 3 -6 h, which was made from hydrogenation-dehydrogenation(HDH) powder(average particles size is 45 μm), have a relative density of 95.6%- 96.7%, ultimate tensile strength of 648 - 686MPa and 0.2% yield strength of 526 - 615MPa; but a lower elongation(＜4%) and that the compacts sintered at 1 260 ℃ for 2 - 6 h, which was made from 90% gas-atomized powder(average particles size is 32.5 μm) and 10 % HDH powder, have higher relative density(＞95 %), ultimate tensile strength of 800 -848MPa,0.2% yield strength of 712 - 762MPa and high elongation (7.4%- 9.5%). When the sintering time is increased,porosity decreases and microstructure of sintered products changes from equiaxed to typical Widmanstatten, the average sizes of prior β grains, α colonies and α phase thickness in the β grains increase accordingly. After HIP treatment,pores obviously become less, microstructure of alloy is refined and mechanical properties are greatly improved.     

固溶处理对注射成形0Cr17Mn11Mo3N钢组织性能的影响

采用金属粉末注射成形工艺制备出了0Cr17Mn11Mo3N高氮无镍奥氏体不锈钢(含氮0.78wt%),研究了固溶处理对力学性能和组织的影响.结果表明,固溶处理能极大改善材料组织和性能,未固溶处理试样组织主要为奥氏体、铁素体以及在晶界连成网状的Cr2N析出物,固溶处理后得到了均一的全奥氏体孪晶组织;固溶处理后力学性能大大提高,抗拉强度和伸长率分别为885MPa和26.0%,为未固溶试样的1.3倍和2.2倍;未固溶处理试样断口为沿晶和韧窝断裂特征,固溶处理试样为韧窝延性断裂特征.     

Rheological, mechanical and corrosive properties of injection molded 17-4PH stainless steel

The feedstock based on the binder 65％PW-30％ EVA-5％SA has the best general rheological properties for the 17-4PH stainless steel powder. The 17-4PH stainless steel compacts sintered at 1380℃ for 90 min have the best mechanical properties and the good microstructure with homogeneously distributed pore structure and the moderate-sized grains. Whereas the compacts sintered for 60 min and 120 min show an inadequate and an over-sintered microstructure respectively. The compacts sintered at 1380℃ for 90 min have the density of 7.70 g/cm^3 , the strength of 1 275 MPa, the elongation of 5％, and hardness of HRC36. With the increase of sintering temperature, the density, strength and hardness increase, while the elongation decreases. The 17-4PH stainless steel has good corrosion resistance, showing an activation-passivation polarization curve. But the passivation potential range is narrow and the spot corrosion potential is low, indicating a low anti-spot corrosive properties.     

Mechanical properties and expansion coefficient of Mo-Cu composites with different Ni contents

Mo-Cu composites were fabricated by powder metallurgy with addition of various Ni contents.The effect of Ni contents on mechanical and thermal properties of Mo-Cu composites was investigated.The results show that mechanical and thermal properties of Mo-Cu composites are greatly affected by the addition of Ni contents.The composite powders with Ni addition exhibits high sinterability.The sintering temperature is greatly decreased and the comprehensive properties of Mo-Cu composites are obviously improved.Mo-Cu composites with a content of 1.5 wt.％ Ni have relative density 99.2％,bending strength 1057.9 MPa,hardness 72.5 HRA,electronic resistivity 1.28× 10 -7Ω.m-1,thermal conductivity 139 W·m-1·K-1,and lower coefficient of thermal expansion 7.4×10-6 K 1.Mo-Cu composites have homogeneous and fine microstructure.The fracture mechanism is ductile fracture.     

热处理对ZG34Cr2Ni2Mo低合金钢力学性能的影响

采用光学显微镜、扫描电镜、电子万能试验机和显微硬度仪等研究了正火+回火+调质热处理工艺对ZG34Cr2Ni2Mo低合金钢显微组织及力学性能的影响.结果表明:正火(870℃×3 h)+回火(600℃×5 h)+调质(淬火860℃×3 h+回火600℃×5 h)的热处理工艺有助于提高ZG34Cr2Ni2Mo低合金钢的力学性...     

低温形变热处理制备Mg-6Gd-1Y-0.5Zr合金的力学性能(英文)

对固溶态的Mg-6Gd-1Y-0.5Zr合金进行低温形变热处理,处理工艺包括不同应变量的冷拉伸和随后在200°C进行的峰值时效。结果表明:低温形变热处理合金的时效硬化动力学显著加速,随变形量增大,合金的峰值时效时间大幅度缩短。冷拉伸变形量为10%的合金在200°C峰值时效后的屈服强度、抗拉强度和伸长率分别达到251MPa、296MPa和8%,这些性能大大超过传统商业牌号的耐热镁合金WE54,尽管其总的稀土含量高于GW61K合金。     

高温时效对00Cr13Ni6Mo2不锈钢组织及性能的影响

采用拉伸试验、X射线衍射、光学显微镜和透射电镜等研究了一种13Cr超级马氏体不锈钢(00Cr13Ni6Mo2)的高温力学性能和高温时效后的力学性能、物相组成及显微组织。结果表明:00Cr13Ni6Mo2钢在高温下可保持较高的屈服强度,但当超过Af(奥氏体转变完成点)温度后,屈服强度迅速下降;600℃时效后,马氏体基体中的位错密度明显降低,同时产生了一定量的逆变奥氏体,导致时效100 h后其屈服强度从824 MPa降至682 MPa(下降17.2%),而抗拉强度和伸长率变化不大;800℃时效过程中,试验钢的组织完全奥氏体化,在降温过程中组织转变为淬火马氏体,故其具有典型的淬火马氏体性能特征,时效100 h后抗拉强度从858 MPa升至1031 MPa(提高20.2%),同时伸长率从22.5%降至15.0%。     

Microstructure and properties of high silicon aluminum alloy with 2% Fe prepared by rheo-casting

The morphology changes of both Fe-containing intermetallic compounds and the primary Si phase of Al-20Si-2Fe- 2Cu-0.4Mg-1.0Ni-0.5Mn (mass fraction, %) alloy produced by semi-solid rheo-diecasting were studied. The semi-solid slurry of high silicon aluminum alloy was prepared by direct ultrasonic vibration (DUV) which was imposed on the alloy near the liquidus temperature for about 2 min. Then, standard test samples of 6.4 mm in diameter were formed by semi-solid rheo-diecasting. The results show that the DUV treatment suppresses the formation of needle-like β-Al₅(Fe, Mn)Si phase, and the Fe-containing intermetallic compounds exist in the form of fine Al₄(Fe, Mn)Si₂ particles. Additionally, the primary Si grows up as fine and round particles with uniform distribution in a(Al) matrix of this alloy under DUV treatment. The tensile strengths of the samples at the room temperature and 573 K are 230 MPa and 145 MPa, respectively. The coefficient of thermal expansion (CTE) between 25 °C and 300 °C is 16.052 8×10^?6 °C^?1, and the wear rate is 1.55%. The hardness of this alloy with 2% Fe reaches HB146.3. It is discovered that modified morphology and uniform distribution of the Fe-containing intermetallic compounds and the primary Si phase are the main reasons for reducing the CTE and increasing the wear resistance of this alloy.     

Effects of molybdenum on the microstructure and mechanical properties of Ti（C,N）-based cermets with low Ni

The effects of Mo on the microstructure and mechanical properties of Ti（C,N）-based cermets with low Ni have been studied systematically. Different contents of Mo （4-12 wt.%） were added into Tl（C,N）-based cermets. Specimens were fabricated by conventional powder metallurgy and vacuum sintered at temperatures of 1440, 1450, and 1460℃ individually. The microstructure and fracture morphology were investigated by scanning electron microscope, and the mechanical properties such as transverse strength and hardness were measured. The results show that the microstructure is uniform and the thickness of rim phase is moderate when the content of Mo is 8 wt.%; the mechanical properties of the specimens sintered at 1450℃ are better than those sintered at 1440 and 1460℃. The integrated properties of transverse strength and hardness are the best when the content of Mo is 8 wt.% and the sintering temperature is 1450℃.