Influence of technical parameters on strength and ductility of AlSi9Cu3 alloys in squeeze casting

An orthogonal test was conducted to investigate the influence of technical parameters of squeeze casting on the strength and ductility of AISigCu3 alloys. The experimental results showed that when the forming pressure was higher than 65 MPa, the strength （ab） of A1Si9Cu3 alloys decreased with the forming pressure and pouring temperature increasing, whereas ab increased with the increase of filling velocity and mould preheating temperature. The ductility （6） by alloy was improved by increasing the forming pressure and filling velocity, but decreased with pouring temperature increasing. When the mould preheating temperature increased, the ductility increased first, and then decreased. Under the optimized parameters of pouring temperature 730 ℃, forming pressure 75 MPa, filling velocity 0.50 m/s, and mould preheating temperature 220 ℃, the tensile strength, elongation, and hardness of A1Si9Cu3 alloys obtained in squeeze casting were improved by 16.7%, 9.1%, and 10.1%, respectively, as compared with those of sand castings.

Tensile properties of high strength cast Mg alloys at room temperature:A review

As most Mg alloy products are now produced by a casting process,the development of high strength cast Mg alloys can promote their further applications and has already become one of the hot research areas of Mg alloys.The present paper reviews the strengthening mechanisms,tensile properties and modification results of commercial high strength cast Mg alloys;as well as the development of Mg-Gd,Mg-Nd and Mg-Sn based alloys.It concludes that precipitation strengthening is the most important strengthening mechanism in high strength cast Mg alloys,which contributes more than 60%of yield strength in solution&peak-aged(T6)cast Mg alloys.For the yield strength,the alloys follow the sequence of Mg-Gd(Y)-Ag>Mg-Gd(Y)-Zn>Mg-Gd-Y/Sm/Nd>Mg-Y-Nd(WE series)>ZK61>Mg-Nd>AZ91>Mg-Sn.Mg-Gd(Y)-Ag based alloys are the strongest cast Mg alloys at present,followed by Mg-Gd(Y)-Zn based alloys.The high yield strengths of Mg-Gd(Y)-Ag and Mg-Gd(Y)-Zn cast alloys are due to the co-precipitation of basal and prismatic meta-stable phases.

Study of rare earth element effect on microstructures and mechanical properties of an Al-Cu-Mg-Si cast alloy

The improvements of microstructures and properties of a high strength aluminum cast alloy were studied. The effects of rare earth elements on the microstructures and mechanical properties of the high strength cast alloy Al-Cu-Mg-Si were investigated. The result shows that the addition of rare earth elements can change the microstructures in refining the grain size of the alloy and making the needle-like and laminar eutectic Si to a granular Si. With the increase of the rare earth, the tensile strength and elongation of the alloy increase first and then fall down. The mechanical properties of the alloy will reach the highest value when the content of rare earth elements is about 0.7%.

Microstructural evolution and enhanced mechanical properties of Mg?Gd?Y?Zn?Zr alloy via centrifugal casting, ring-rolling and aging

A ring-shaped Mg?8.5 Gd?4 Y?1 Zn?0.4 Zr(wt%) alloy was manufactured via centrifugal casting and ring-rolling process. The effects of accumulative ring-rolling reduction amount on the microstructure, texture, and tensile properties of the alloy were investigated. The results indicate that the microstructure of centrifugal cast alloy consists of equiaxed grains and network-like eutectic structure present at grain boundaries. The ring-rolled alloy exhibits a characteristic bimodal microstructure composed of fine dynamic recrystallized(DRXed) grains with weak basal texture and coarse un-DRXed grains with strong basal texture, along with the presence of LPSO phase. With increasing amount of accumulative ring-rolling reduction, the coarse un-DRXed grains are refined via the formation of increasing amount of fine DRXed grains. Meanwhile, the dynamic precipitation of Mg5 RE phase occurs, generating a dispersion strengthening effect. A superior combination of strength and ductility is achieved in the ring-rolled alloy after an accumulative rolling reduction of 80%. The tensile strength of this ring-rolled alloy after peak aging is further enhanced, reaching 511 MPa, while keeping a reasonable ductility. The salient strengthening mechanisms identified include the grain boundary strengthening of fine DRXed grains, dispersion strengthening of dynamic precipitated Mg;RE phase, short fiber strengthening of LPSO lamellae/rods, and precipitation strengthening of nano-sized prismatic β precipitates and basal γ precipitates.

Microstructure Distribution Characteristics of High-Strength Aluminum Alloy Thin-Walled Tubes during Multi-Passes Hot Power Backward Spinning Process

The microstructure of the thin-walled tubes with high-strength aluminum alloy determines their final forming quality and performance. This type of tube can be manufactured by multi-pass hot power backward spinning process as it can eliminate casting defects, refine microstructure and improve the plasticity of the tube. To analyze the microstructure distribution characteristics of the tube during the spinning process, a 3D coupled thermo-mechanical FE model coupled with the microstructure evolution model of the process was established under the ABAQUS environment. The microstructure evolution characteristics and laws of the tube for the whole spinning process were analyzed. The results show that the dynamic recrystallization is mainly produced in the spinning deformation zone and root area of the tube. In the first pass, the dynamic recrystallization phenomenon is not obvious in the tube. With the pass increasing, the trend of dynamic recrystallization volume percentage gradually increases and extends from the outer surface of the tube to the inner surface. The fine-grained area shows the states of concentration, dispersion, and re-concentration as the pass number increases. .

功率超声对水平连铸Al-1％Si合金凝固的影响

研究了水平连铸过程中在保温炉内施加功率超声熔体处理对Al-1％Si合金凝周过程的影响。结果表明:施加功率超声后,合金凝固曲线第1个拐点左移,斜率发生了变化,且随着超声功率的增加,合金的结晶温度升高,当超声功率为1000 W时,结晶温度提高了33℃;同时,施加了功率超声后,保温炉内金属液温度分布均匀性随着超声功率的增加得到了显著的改善;金相分析表明,当超声功率为1000 W时,铸坯凝固组织得到了细化,同时晶粒尺寸更加均匀;此外,施加功率超声处理后铸坯表面质量得到了提高。

连铸保护渣结晶性能与16Mn铸坯表面微裂纹的关系

针对 16Mn系列高强度低合金钢连铸坯轧制中厚板生产中 ,因表面微裂纹钢板报废率高的问题 ,在采用镀层结晶器的基础上 。

高强度铸造铝合金ZL107A的时效过程

利用透射电镜（ＴＥＭ）观察了高强度铸造铝合金ＺＬ１０７Ａ的时效过程。合金中的Ｃｄ改变了时效过程中ＧＰ区的发展序列，即Ｃｄ强烈抑制Ｇｐ区形成，促进θ″和θ′的析出。大量细小弥散分布的θ″和θ′显著地提高合金的强度。

压铸高强韧Al-Cu系合金的组织性能及热处理探讨

为了弥补目前压铸铝合金强韧性不足,进行了高强韧Al-Cu系合金的压铸及热处理的试探性研究。在ZL201的基础上,添加合金化元素B、Zr、V等,改善合金的铸造性能,进行压铸成形试验。试验研究发现压铸大大细化了合金的微观组织,铸态性能较金属型高,再经低温时效后合金强度达到一般高强压铸铝合金的水平,但塑性较之提高20%以上。

Al-Cu系合金的压铸及热处理实践

为了弥补目前压铸铝合金强韧性不足,进行了高强韧铝铜系合金的压铸及热处理的试探性研究。在Zl201的基础上,调整合金成分,改善合金的铸造性能,进行压铸试验研究。试验发现压铸大大细化了合金的微观组织,铸态性能较金属型高,经低温时效后合金强度达到一般高强压铸铝合金的水平,且塑性提高20%以上。

一种新型高强韧铸造铝硅合金(ZL120)热处理工艺的研究

对一种新型高强韧铸造铝硅合金 (暂名ZL1 2 0 )的T6热处理工艺进行了研究 .对固溶温度Ts、固溶时间ts、时效温度Ta和时效时间ta进行三水平正交试验 ,并测试了该合金在对应处理状态下的力学性能 ,然后根据此结果再进行验证性试验 .结果表明 ,改变这四个参数可得到一系列的性能组合 ,例如 ,热处理工艺为 5 2 0℃× 1 6h+ 60℃水冷 + 1 70℃ × 8h时 ,可获得抗拉强度σb ≥ 40 0MPa和延伸率δ5 ≥ 3 %的力学性能 .

汽车用高强度钢CR1030/1300MS连铸板坯的热塑性

试验用CR1030/1300MS钢236 mm×1 350 mm连铸板坯(/%:0.13C,0.26Si,1.53Mn,0.011P,0.002S,0.31Cr,0.047Als,0.029Nb,0.032Ti,0.002 5B,0.003 2N)的工艺流程为260 t BOF-LF-RH-CC。采用Gleeble3500热模拟试验机测试了试验板坯650～1 300℃的热塑性曲线,并分析了高温拉伸试样断口组织。试验结果得出,试验钢两个脆性区为熔点～1 120℃和800～650℃在1 120-800℃呈现良好的塑性,断面收缩率均在85%以上。900℃断口属于穿晶韧性断裂,700℃为韧性和沿晶断裂。1 250℃和900℃近断口组织均为马氏体,温度升高马氏体板条更粗大。750℃原奥氏体晶界出现先共析铁素体是产生裂纹的根本原因。1 120～800℃进行矫直可防止铸坯产生裂纹。

铸态高强度高韧性QT600-10球墨铸铁控制技术

以铸态QT600-10材质生产技术为例,简要介绍了铸态高强度高韧性球墨铸铁件控制要点:根据铸件壁厚条件,碳(C)控制在3.6%~3.8%、硅(Si)2.5%~2.8%、锰(Mn)<0.3%,采用微合金化时,控制铜(Cu)0.20%~0.50%、锡(Sn)0.02~0.05%。熔炼时采用C高Si低,CE适中,Mn、S、P低,采用低稀土Si-Mg6-8RE1-5球化剂,采用常规75SiFe孕育剂或长效孕育剂,通过控制基体组织比例,达到高强度高韧性铸态QT600-10的要求。

Influence of neodymium on high cycle fatigue behavior of die cast AZ91D magnesium alloy

High cycle fatigue behavior of die cast AZ91D magnesium alloy with different Nd contents was investigated.Axial mechanical fatigue tests were conducted at the stress ratio R=0.1 and the fatigue strength was evaluated using up-to-down load method on specimens of AZ91D with different Nd contents.The results showed that the grain of AZ91D alloy was refined,the size and amount of β-Mg17Al12 phase decreased and distributed uniformly with increasing Nd content.At the number of cycles to failure,Nf=107,the fatigue...

800MPa级Al-Zn-Mg-Cu系合金

通过采用在线精炼、在线细化、热顶铸造等技术手段,成功在直接水冷半连续铸造设备上制备出了合金化元素总量达20%的Al-Zn-Mg-Cu系合金,打破了7000系铝合金合金化元素总量不高于14%的极限。利用金相显微镜、透射电镜进行微观组织观察,采用差热分析仪测试相转变温度,测试了硬度、拉伸性能并利用扫描电镜进行断口分析。该合金经过挤压、RRA热处理后,其抗拉强度、屈服强度和伸长率分别达到810.3,799.3MPa和3.4%。通过对单级时效动力学和三级时效动力学进行研究,确定了合金的最佳时效温度为120℃,而时效时间的可选择范围较大。Zn含量高达16.1%的铝合金中主要由未溶第二相和时效析出相η′相共同强化,未发现其他新析出相。

虎门二桥1960 MPa主缆钢丝及索股关键技术

依托虎门二桥坭洲水道桥(主跨1 688m的双塔双跨悬索桥),系统开展了1 960MPa主缆钢丝及索股的技术开发。研制了适用于在线水浴、离线盐浴、离线铅浴等不同索氏体化方式的国产1 960 MPa钢丝盘条,性能指标优于国外同类产品。通过超高强度钢丝拉拔工艺、"双镀+电磁抹拭"热镀锌铝工艺、稳定化处理工艺,研发了抗拉强度达1 960MPa、扭转次数≥14次的高强度锌铝合金镀层钢丝,并形成完整的生产工艺体系。开发了1 960 MPa悬索桥主缆索股技术及具有优异锚固性能、静载性能、抗疲劳性能和抗滑移性能的锚固系统,实现了30 000余吨1 960 MPa镀锌铝合金钢丝索股在虎门二桥工程中的应用。

电渣熔铸ZG14Ni3CrMoV低合金高强度钢力学性能研究

以ZG14Ni3CrMoV低合金高强度钢为原料,研究了电渣熔铸ZG14Ni3CrMoV的微观组织和力学性能。试验结果表明:ZG14Ni3CrMoV的微观组织主要变化温度为400℃、497℃、745℃、800℃、892℃、1080℃,通过试样的微观组织变化机制,制定了自耗电极和电渣熔铸钢锭的热处理工艺。热处理后电渣熔铸钢锭的金相组织主要为回火索氏体,细小且均匀;电渣熔铸钢锭的拉伸性能:R_(m)为684 MPa、R_(p0.2)为567 MPa、A为24%、Z为72%,X向及Y向的性能差异较小,拉伸断口韧窝尺寸均一、形状统一、分布均匀、深度基本一致且韧窝壁清晰光滑;电渣熔铸钢锭的冲击性能:-20℃为216 J、-40℃为172 J、-60℃为140 J、-80℃为102 J、-100℃为49 J,低温冲击性能裕量充足,相较于自耗电极有较大提升,冲击断口为典型韧性断裂。

铸态QT700-2偏心体铸件的研发

本文介绍铸态QT700-2偏心体铸件的研发过程。在铸造工艺方案上采用分层浇注,在铸件热节部位使用冷铁,并且结合保温冒口工艺,使铸件达到均衡凝固,消除铸件的缩松、缩孔缺陷;在熔炼过程通过合金化,使用低稀土球化剂,采用多次孕育处理,消除了碎块状石墨、细化了石墨晶粒、稳定了珠光体含量,生产的铸态偏心体的性能满足客户要求。

高强度低应力铸铁件铸造工艺研究与生产应用

就机床铸件的变形、开裂等失效问题,对国外高端数控机床铸件结构和材料等生产控制技术进行了相关研究,发现机床失效的主要问题点在铸件的结构强度低和材料刚性差,使得铸件应力变大,机床因铸件应力释放而发生变形,精度丢失。通过铸造模拟分析,反向优化铸件结构、浇注系统等,以高碳当量+复合合金化的熔炼工艺,配合复杂的时效工艺,实现了高强度低应力铸件的生产。

超高强桥梁缆索用多元合金锚固材料研究

桥梁缆索采用热铸锚方式锚固,具有强度高、耐久性好的优点,适于缆索百年服役的要求。分析了热铸锚的结构和锚固机理,合金锚固材料是影响热铸锚锚固性能和耐久性的主要因素,而Al,Cu,Mg,RE等成分和含量决定了合金锚固材料的性能。针对2100 MPa及以上强度超高强缆索,提出了热铸锚用合金锚固材料的物理性能、力学性能、防腐性能和流动性要求。根据这些影响因素和性能要求,建议按“性能指标构建-成分体系设计-模型试验研究-灌锚装备研发-灌锚工艺研究”的路线进行新型多元合金锚固材料研究。