60Si2Mn半固态浆料的制备和流变轧制的组织形貌

以弹簧钢（60Si2Mn)为研究对象，采用电磁搅拌的方式制备半固态浆料，研究了搅拌参数对半固态浆料组织形貌的影响；同时对半固态浆料进行了流变轧制，观察和分析了半固态浆料在轧制过程中的组织演变及轧制产品可能存在的组织缺陷。结果表明：在变温连续搅拌条件下，随着搅拌时间的延长，半固态浆料的固相率提高，初生固相颗粒的直径减小，组织更均匀；经过1道次的轧制，半固态浆料中的液相从固相颗粒间挤出，流向轧件的表面，大部分固相集中在轧件的中心，产生宏观偏析现象，提高固相率可减小偏析程度。此外，轧件中还可能出现缩孔、分层组织等缺陷。     

半固态60Si2Mn直接轧制成形技术的研究

利用自行研制的高熔点半固态金属材料的轧制设备，对60Si2Mn弹簧钢进行半固态直接轧制成形，并研究流变行为和规律，探索出适合于半固态钢铁材料直接轧制成形的生产工艺。研究结果表明：固－液两相的塑性变形行为是不同的，从而导致了轧制产品的心部和边部在组织及性能上的差异。在变形过程中，大多数的固相集中在试样的心部，而液相则流向轧件的边部。随着固相率的提高，固相颗粒发生塑性变形的程度亦提高。若半固态浆料中液相含量过少或变形速率过大，轧辊表面与轧件的温差过大，则轧件的表面会产生微小的裂纹。     

1Cr18Ni9Ti的流变浆料制备和直接轧制试验

利用自行设计装置进行1Cr18Ni9Ti不锈钢的半固态流变浆料制备和半固态流变浆料的直接轧制试验。结果表明：在本试验条件下制备的1Cr18Ni9Ti不锈钢半固态流变组织中先结晶的奥氏体呈近球状，尺寸在100－200μm，半固态流变浆料的固相率为50%-60%；该流变浆料具有较好的流动性，在半固态直接轧制成形过程中会产生液相偏析和一定程度的固相颗粒塑性变形。     

1Cr18Ni9Ti的流变浆料制备和直接轧制试验

利用自行设计装置进行 1Cr18Ni9Ti不锈钢的半固态流变浆料制备和半固态流变浆料的直接轧制试验。结果表明 :在本试验条件下制备的 1Cr18Ni9Ti不锈钢半固态流变组织中先结晶的奥氏体呈近球状 ,尺寸在 10 0～ 2 0 0 μm ,半固态流变浆料的固相率为 5 0 %～ 60 % ;该流变浆料具有较好的流动性 ,在半固态直接轧制成形过程中会产生液相偏析和一定程度的固相颗粒塑性变形     

半固态Al-Zn-Mg-Cu合金的拉伸力学行为（英文）

为了研究半固态成形过程中的热裂现象,在高温固态和半固态及不同应变速率对Al-Zn-Mg-Cu系挤压态7075铝合金进行拉伸试验。结果表明:随着液相率的升高,7075铝合金在拉伸过程中表现为3种变形机制。首先,合金表现为典型的塑性变形特征;随着温度升高,合金的变形行为由固相和液相共同决定,变形特点由塑性向脆性转变;液相率更高时,合金的变形行为完全由液相决定,并表现为明显的脆性变形特点。在应变速率分别为1×10~(-4)、1×10~(-3)和1×10~(-2) s~(-1)时,合金的脆性温度区间分别为515~526、519~550和540~580℃。此外,建立了关于拉伸行为的两个关键方程。     

ZL101半固态微压缩实验研究

对ZL101合金进行不同温度和保温时间的重熔处理,获得不同半固态组织状态,并进行常规尺寸(Φ5 mm)和微观尺寸(Φ1 mm)试样的等温压缩实验,得到不同变形温度和保温时间下试样的流变应力曲线,通过两种尺寸的力学性能比较,获得半固态金属在尺寸微型化的过程中尺度效应的存在条件与存在形态。研究表明,ZL101铝合金在常温和高固相率条件下均存在着流动应力增加的尺度效应现象;在高固相率条件下流动应力增大的现象更加明显;增加保温温度和保温时间,固相球化率增加,可以削弱流动应力增加的尺度效应。     

温度对AZ31镁合金半固态铸轧组织的影响

数值模拟和试验研究了不同温度下半固态铸轧AZ31镁合金的铸轧过程温度场和微观组织。结果表明,在不同的铸轧温度下,铸轧过程温度场不相同,要顺利进行铸轧就需要不同的冷却系统。铸轧温度从高到低,半固态固相颗粒明显从小到大,固相率也变大。特别是在623℃到620℃之间固相率较高,固相颗粒接近球形,是典型的半固态组织。     

机械搅拌法制备半固态镁合金的组织及性能研究

采用AZ91D镁合金为试验原料,以本课题组自行研制的新型半固态浆料制备与直接流变成形装置为试验设备,研究不同温度、剪切速率下半固态组织的变化规律和不同的成型工艺对其力学性能的影响.研究表明:制备浆料的温度相对越低,剪切速率越大,固相率越高,固相颗粒越细小、均匀、圆整;在3种成型工艺中,半固态挤压铸造的综合力学性能相比来说最好,半固态普通铸造次之,铸态普通铸造最差.     

轧制-重熔SIMA法制备ZCuSn10合金半固态坯料

采用轧制-重熔的SIMA法制备了ZCuSn10合金半固态坯料,先将铸态ZCuSn10合金加热到450℃保温15 min,分别进行2~4道次轧制,然后截取试样进行重熔处理后水淬.比较了SIMA法和铸态-直接重熔工艺制备的ZCuSn10合金半固态组织,并利用SEM的EDS测定了组织中Sn的分布情况,用OM和TEM观察了SIMA法制备过程中试样组织变化,综合分析了SIMA法制备ZCuSn10合金半固态坯料过程中的组织演变机理.结果表明:采用轧制-重熔的SIMA法制备的ZCuSn10合金半固态组织固相晶粒均匀细小,圆整度高,19.7%预变形量875℃保温15 min半固态组织最优,其平均晶粒直径75.8μm,形状因子1.62,液相率17.28%;用SIMA法制备ZCuSn10合金半固态坯料,预变形过程对晶粒细化及球化起到了关键作用,随着预变形量和重熔保温温度的提高,半固态组织晶粒尺寸减小,圆整度提高,液相率增加;采用轧制-重熔的SIMA法制备ZCuSn10合金半固态组织球化的主要机理是预变形过程破碎了枝晶,储备了变形能,在重熔过程中促进了枝晶熔断,同时,由于Sn元素从液相中向a固相中扩散迁移,液相逐渐吞噬固相的尖角突出部分,最终生成细小、圆整的a相晶粒.     

1Cr18Ni9Ti不锈钢半固态浆料的制备和轧制

研究了1Cr18Ni9Ti不锈钢半固态浆料的制备和轧制规律，结果表明：在本实验条件下，当搅拌时间为2—3min时，可以获得尺寸大小为10m-200μm、固相率为50％—60％的球状初生奥氏体的半固态浆料，便于从搅拌室底孔中放出，浆料可以实现顺利轧制，但球状初生固相颗粒与液相发生了分离，球状初生固相颗粒集中在轧材的心部，而液相偏聚在轧材的四周；经过一道次轧制，1Cr18Ni9Ti不锈钢半固态浆料轧制板材的常温强度比常规热轧板材的强度高，但延伸率下降。     

MICROSTRUCTURE EVALUATION OF SEMI-SOLID STEELMATERIALS IN ROLLING PROCESS AND THERESULTING MECHANICAL PROPERTIES

1. IntroductionSemi-solid metal processing is a kind of near net-shape forming technology which hasbeen taken into account by the researchers all over the world. At present, six internationalconferences have been held. The semi-solid steel slurry direct rolling--rheorolling combinesthe fabrication of the semi-solid slurry with continuously rolling. This technology is differ-ent from the present rolling methods which are based on the dendritic .tructu.el1t2]. It is aneoteric rolling processing…     

ART退火后冷却方式对0.1C-7.2Mn钢加工硬化行为的影响

以0.1C-7.2Mn热轧和冷轧中锰钢为研究对象,采用扫描电镜(SEM)、X射线衍射仪(XRD)、室温拉伸试验等手段,研究了奥氏体逆相变(ART)退火后不同冷却方式对中锰钢加工硬化行为的影响。结果表明,热轧试验钢ART退火后得到板条状铁素体-奥氏体组织,退火后空冷试样中有大量碳化物析出,而水冷抑制了碳化物析出。冷轧试验钢ART退火后得到了等轴状铁素体-奥氏体组织,退火后空冷试样表现为连续屈服,而水冷促进了组织的等轴化;热轧试样获得更高体积分数的残留奥氏体,获得了优异的力学性能;残留奥氏体体积分数越大,拉伸变形过程中发生的TRIP效应越持久,提供更高、更持续的加工硬化。     

Deformation characteristic of semi-solid ZCuSn10 copper alloy during isothermal compression

The compression tests were carried out by Gleeble-1500 thermo-mechanical simulator with samples of semi-solid ZCuSn10 alloy prepared by strain-induced melt activation(SIMA) process. The original microstructure and the deformation temperature of semi-solid ZCuSn10 alloy are different. The strain is 0.2, and the strain rate is 1 s~(-1) for the compression test. The results show that when the semi-solid ZCuSn10 alloy was prepared by SIMA process, the liquid fraction of semi-solid microstructure increases, and the solid grain is smaller,more uniform and more inclined to be round as the rolling pre-deformation increasing. The results also indicate that the deformation resistance of ZCuSn10 alloy in semi-solid state decreases with the deformation temperature increasing or the solid fraction of original microstructure decreasing. The stress–strain curves of the isothermal compression can be divided into quasi-elastic deformation stage and plastic deformation stage, and there are three deformation zones in the samples after isothermal compression, namely the difficult deformation zone, the large deformation zone and the free deformation zone. In the three deformation zones, the main deformation mechanism is flow of liquid incorporating solid particles(FLS)mechanism, plastic deformation of solid particles(PDS)mechanism and liquid flow(LF) combining with FLS mechanism, respectively.     

Deformation mechanism and forming properties of 6061Al alloys during compression in semi-solid state

The 6061 semi-solid aluminium alloy feedstocks prepared by near-liquidus casting were compressed in semi-solid state by means of Gleeble-3500 thermal-mechanical simulator. The relationship between the true stress and the true strain at different temperatures and strain rates was studied with the deformation degree of 70%. The microstructures during the deformation process were characterized. The deformation mechanism and thixo-forming properties of the semi-solid alloys were analyzed. The results show that the homogeneous and non-dendrite microstructures of semi-solid 6061Al alloy manufactured by near-liquidus casting technology could be transformed into semi-solid state with the microstructure suitable for thixo-forming which are composed of near-spherical grains and liquid phase with eutectic composition through reheating process. The deformation temperature and strain rate affect the peak stress significantly rather than steady flow stress. The resistance to deformation in semi-solid state decreases with the increase of the deformation temperature and decrease of the strain rate. At steady thixotropic deformation stage, the thixotropic property is uniform, and the main deformation mechanism is the rotating or sliding between the solid particles and the plastic deformation of the solid particles.     

轧制变形对CrCoNi中熵合金组织及性能的影响

通过真空悬浮熔炼炉熔炼制备了CrCoNi中熵合金,采用900 ℃热轧(变形量50%)、500 ℃温轧(变形量50%)获得轧制板材,利用光学显微镜、X射线衍射仪、扫描电镜、硬度计和万能试验机,研究轧制变形对合金组织结构和力学性能的影响。结果表明:CrCoNi中熵合金铸态时为简单的单相FCC固溶体结构,随着轧制变形的进行,无新相产生;CrCoNi合金有较好的塑性变形能力,塑性变形后其力学性能得到大幅度的提升,热轧后,其抗拉强度能达到890 MPa,伸长率能达到60%,并且通过加大变形量以及热轧+温轧的组合可实现强度的进一步的提升;严重的晶格畸变、加工硬化以及细晶强化共同促进了其高强度与良好韧性的结合。     

Forming of aluminium alloy at temperatures just below melting point

In order to improve the mechanical properties of products, a forming process of a solid material at a temperature just below the melting point is proposed. The material is deformed at the semi-solid temperature due to the heat generation caused by plastic deformation. The tensile strength, elongation, hardness and toughness of the aluminium alloy (Al–7%Si–0.3%Mg) billet extruded at temperatures between 500 and 550 °C are compared with those of the billet extruded in the hot forming (450 °C) and the semi-solid (560 °C) temperatures. The billet temperature during forming is evaluated by the finite element simulation. The tensile strength and hardness of the billet extruded at 550 °C just below the solidus temperature are higher than those for a billet at 450 °C, and they are almost the same as those for a billet deformed at 560 °C in the semi-solid region. The elongation and toughness of the extruded billet at 550 °C are lower than those for a billet at 450 °C. The forming load at 550 °C is almost half of that at 450 °C. Cracking on the surface of the extruded billet occurs at a high punch speed. The calculated temperature when the solid billet is extruded in the semi-solid state agrees well with the experimental one at which the tensile and hardness are improved.     

TWIP钢不同温度变形的力学性能变化规律及机理研究

通过控温拉伸实验分析了在298,373,473和673 K温度下变形时,TWIP钢(Fe-25Mn-3Si-3Al)力学性能和显微组织的变化规律.结果表明,TWIP钢的强度和延伸率均随温度的升高而降低.通过热力学公式对不同温度下TWIP钢层错能Γ的估算可以推断,温度T≥673 K时,Γ≥76 mJ/m2,滑移为TWIP钢主要的变形机制;298 K≤T≤373 K时,21 mJ/m2≤Γ≤34 mJ/m2,孪生为TWIP钢主要的变形方式,此时产生"TWIP"效应,可获得较高的加工硬化速率,从而获得高强度及高塑性.