CX型长效无公害铝硅合金变质剂的应用

本文介绍了ＣＸ型长效无公害铝硅合金变质剂对ＺＬ１０８和ＺＬ１０４合金的变质效果。结果表明：该变质剂对铝硅合金有双重变质作用，可同时细化和改善初生硅和共晶硅形貌，且具有速效和持效作用，提高铝硅合金的力学性能和铸件的使用性能；该变质剂加入量少，变质工艺简便，处理时无烟雾、粉尘和刺激性气味，具有良好的技术经济效果。     

氧化镧对铝硅合金变质的研究

本论文通过加入一定熔剂的氧化镧对铝硅共晶合金的变质处理试验,开发出以氧化镧为基的LYLM变质剂。此变质剂对铝硅合金变质不仅具有良好的变质作用而且拥有良好的抗衰退性和保温性能．当在铝硅共晶合金中加入最佳加入量0．5～1.0％人wtLYLM变质剂后,其抗拉强度和延伸率分别提高了58％和289％．并且保温6h．重熔13次时,合金仍具有相当的强．度和延伸率．本文通过LYLM变质剂反应模型的建立,揭示了氧行镧是通过络合反应过程对铝硅合金起变质作用的．     

过共晶铝硅合金变质处理的研究进展

综述了过共晶铝硅合金变质处理及其细化变质机理的研究进展.采用含磷化合物或含磷合金等细化变质处理过共晶铝硅合金中的初晶硅已取得了良好的效果;变质元素Na、Sr、Ba、Te、Sb、S、Y、Ca、Bi、As、Ce、Nd、RE等元素对共晶硅具有较好的细化变质作用;近年来,同时添加磷和混合稀土复合变质剂,既能细化初晶硅,又能细化共晶硅.寻求具有良好双重变质效果的复合变质剂,深入探讨变质机理已成为今后努力的方向.     

稀土在过共晶Al-Si合金中的变质作用

分析了稀土合金变质处理过共晶铝硅合金硅相的形态变化过程。认为稀土除能细化共晶硅外,也能细化初生硅,是一种优良的变质剂。RE的变质机制与Na不同,稀土是通过造成硅相前沿大的成分过冷来促进硅晶分枝而达到变质目的的。     

Al-10Ce中间合金对ZL102合金的变质研究

用光学显微镜(OM)等分析研究Al-10Ce中间合金对ZL102共晶铝硅合金的变质处理效果.结果表明.Al-10Ce中间合金用量、熔体中的杂质以及冷却速度对变质效果的影响很大.Al-10Ce中间合金用量为0.9%左右时达到最佳变质效果,用量少变质效果差,用量过多则形成过变质.通过提高Al-Si的纯度可以获得变质组织.冷却速度超过70℃/min时才具有明显的变质效果.由于冷却强度不同,铸棒中心部位变质效果比边部差.Al-10Ce中间合金对共晶铝硅合金变质处理时间较短.     

碳酸镧对铝硅合金变质的研究

本文通过加入一定熔剂的碳酸镧对铝硅共晶合金的变质处理试验,开发出以碳酸镧为基的LCLY变质剂,此变质剂对铝硅合金变质不仅具有良好的变质作用而且拥有良好的抗衰退性和长效性。当在铝硅合金中加入最佳加入量0．3～0．6％WtLCLY变质剂后,其抗拉强度和延伸率分提高了35．1％和199．6％,并且保温6h,重熔13次时,合金仍具有相当的强度和延伸率。本文过LCLY变质剂反应模型的建立,揭示了LCLY变质剂变质机理,并通过正交实验,确定了其最佳变质工艺。     

锶在铸造铝硅合金中的变质行为

最为人们接受的硅的变质机理是杂质诱发孪晶假说.锶的变质能力强,且变质有效期长.锶的孕育期的长短主要与铝硅合金液中磷的含量有关.由于共晶硅中的孪晶密度随硅的生长速度的降低而减少,锶变质要求合金冷却速度要高于一定的临界值.磷、锑、铋、钙、稀土等元素对锶的变质有毒化作用.锶变质会导致铸件中孔洞的增加.     

铝硅合金变质机理的新发展和新观点（上）

铝硅合金变质机理的新发展和新观点（上）上海交通大学黄良余自２０年代初发现Ａｌ－Ｓｉ合金变质现象能明显提高合金的力学性能、切削性能以来，已过去７０余年，为揭开Ａｌ－Ｓｔ合金的变质机制，世界各国的冶金工作者进行了大量的试验研究工作，随着现代测试技术的出现...     

CeF钠盐变质剂在生产中的应用

探讨ＣｅＦ钠盐变质剂在活塞生产条件下对ＺＬ１０８合金的变质作用。试验结果表明该变质剂对ＺＬ１０８合金具有良好的中效变质作用，变质有效时间保持２．５ｈ以上，能使合金的室温抗拉强度和延伸率分别提高４６％和４０％，同时降低合金的粘度，利于活塞成型。     

氯化稀土变质剂在ZL107A合金中的实际应用

本文研究了氯化稀土变质剂在工业生产条件下对ZL107A合金的变质作用。试验结果表明该变质剂在生产条件下,仍对合金具有良好的长效变质作用,能使ZL107A合金的室温抗拉强度和延伸率分别提高28％和70％,同时降低合金的针孔度,该变质剂价格低廉,操作简单,且对环境污染小,利于在生上推广应用。     

功率超声对Al—Si合金组织和性能的影响

研制成功率超声铸造设备和附属装置, 研究了全过程超声处理和结晶前超声处理对ＡｌＳｉ 共晶和过共晶合金铸造组织和性能的影响。结果表明： 适宜的超声参数对初晶Ｓｉ 和共晶Ｓｉ 组织具有双重细化作用, 使Ｓｉ 破碎变成颗粒状, 合金的机械强度和塑性明显提高。认为超声细化合金组织存在阈值声压, 对功率超声细化合金组织的机理进行了理论上的分析和探讨。     

超声处理对Mg-9Al-3Si合金组织及力学性能的影响

研究了超声处理对Mg-9Al-3Si合金凝固组织及力学性能的影响。结果表明,通过控制超声工艺参数可改善Mg-9Al-3Si合金凝固组织,提高其力学性能的目的。在超声功率为0~900W时,随着超声功率增大,合金中的Mg2Si相逐渐细化,其抗拉强度先增后减,转折点为700W。在超声处理时间为0~90s时,随着超声处理时间延长,合金中的Mg2Si相逐渐细化,其抗拉强度先增后减,转折点为60s。分析其断口发现,未经超声处理的合金断裂形式为解理断裂,经过超声处理的合金断口解理台阶尺寸减小,呈准解理断裂特征。     

Degassing effect of ultrasonic vibration in molten melt and semi-solid slurry of Al-Si alloys

In the process of semi-solid slurry preparation with direct ultrasonic vibration (UV) by dipping the horn into the melt, one of the questions is whether the gas content in the melt would be increased or not by the cavitation effect of ultrasonic vibration. By application of quantitative gas content measurement technique, this paper investigated the effect of the ultrasonic vibration on the gas content of both the melt and the semi-solid slurry of Al-Si alloys, and the variations of the gas contents in two kinds of aluminum alloys, i.e., A356 alloy and Al-20Si-2Cu-1Ni-0.6RE alloy (Al-20Si for short). The results show that ultrasonic vibration has an obvious degassing effect on the molten melt, especially on the semi-solid slurry of Al-Si alloy which is below the liquidus temperature by less than 20 ℃. The ultrasonic degassing efficiency of the A356 alloy decreases with the reduction of the initial gas content in the melt, and it is nearly unchanged for the Al-20Si alloy. The gas content of both alloys decreases when the ultrasonic vibration time is increased. The best vibration time for Al-20Si alloy at the liquid temperature of 710 ℃ and semi-solid temperature of 680 ℃ is 60 s and 90 s, respectively; and the degassing efficiency is 48% and 35%, respectively. The mechanism of ultrasonic degassing effect is discussed.     

超声波对Al-20Si合金中初晶Si的影响

采用高能超声波对Al-20Si合金熔体进行处理,研究超声波以不同的导入方式对过共晶Al-Si合金中初晶Si的细化效果的影响。试验表明,在Al-20Si合金凝固过程中进行超声波处理,可以促进形核,破碎组织中粗大块片状初晶Si,减小晶粒尺寸,提高圆整度,并使其分布均匀。由于超声波的衰减效应,采用不同方式导入超声波进行处理时,对合金凝固组织的作用效果有较大区别。采用超声波导入杆在距熔体中心1/2半径处做环绕运动导入超声波,能够对初晶Si产生较好的细化效果,所获得的凝固组织细化区域更大,初晶Si分布更加均匀。     

Effects of ac arc ultrasonic on plasma arc in situ welding of SiCp/6061Al MMCs

Abstract

The isolation coupling device is designed based on the principle of high pass filter circuit, which can achieve isolation and coupling between ac welding power and ultrasonic frequency excitation source. In addition, ac arc ultrasonic vibration is obtained successfully. The plasma arc in situ welding of SiCp/6061Al was performed using two different processes. The first process is that the plasma gas is argon nitrogen mixture and the filler material is flux cored wire (Al–5Ti–5Si); the other process is that the plasma gas is argon and the filler material is flux cored wire (Al–15Ti–3Si). The two joints are respectively enhanced by nitride and Al₃Ti, which were obtained in these processes. After arc ultrasonic vibrations were imposed on the two welding processes, it was revealed that arc ultrasonic improved the distribution of the new nitride phases and optimised the morphology of Al₃Ti to improve the mechanical properties of joints that reached 246 and 263 MPa. Fracture analysis showed that the improvement of the mechanical properties resulting from Al₃Ti is better than that from nitride under the effect of arc ultrasonic.     

镁合金表面超声滚压预处理对微弧氧化膜耐蚀性能的影响

镁合金基体首先进行超声滚压预处理后再进行微弧氧化镀膜,结合OM、SEM、EDS、XRD与电化学工作站(模拟体液PBS)对有无超声滚压处理的微弧氧化膜层性能进行测试分析,研究超声滚压处理对镁合金微弧氧化膜层性能的影响.结果 表明:超声滚压处理后镁基体表面粗糙度降低、晶粒细化且硬度提升;与镁合金直接微弧氧化的膜层相比,超声...     

The role of strontium in modifying aluminium–silicon alloys

Small amounts of strontium can transform the morphology of the eutectic silicon phase present in Al–Si casting alloys from coarse plate-like to fine fibrous networks. In order to understand this industrially important but hitherto insufficiently understood effect, the strontium distribution was studied in atomic resolution by atom probe tomography and in nanometre resolution by transmission electron microscopy. The combined investigations indicate that Sr co-segregates with Al and Si within the eutectic Si phase. Two types of segregations were found: (i) nanometre-thin rod-like co-segregations of type I are responsible for the formation of multiple twins in a Si crystal and enable its growth in different crystallographic directions; (ii) type II segregations come as more extended structures, restrict growth of a Si crystal and control its branching. We show how Sr enables both kinds of mechanisms previously postulated in the literature, namely “impurity-induced twinning” (via type I) and growth restriction of eutectic Si phase (via type II).     

铁基块体非晶合金的空泡腐蚀研究

通过对超声空化作用过程中试样表面物相组成变化和试样失重的实验研究,分析了Fe74Al4Ga2P12B4Si4铁基块体非晶合金的空蚀过程。分别采用处于晶态和非晶态的铁基块体合金,在自来水中进行超声空化实验,确定了材料特性对空蚀过程的影响。结合已有的空泡形成和溃灭理论,初步提出了铁基块体非晶合金的耐空蚀机理。     

Effect of ultrasonic melt treatment on microstructure of A356 aluminium cast alloys

Abstract

A systematic study of the effect of ultrasonic treatment on the structure of the A356 Al–Si–Mg alloy was carried out. Ultrasonic vibrations were applied to the melt at several temperatures (628 to 608°C) for different periods (0–180 s). The results showed that the ultrasonic treatment is effective in controlling the morphology and size of aluminium grains when applied between 619 to 626°C, and is very effective at 622–625°C, where fine non-dendritic grains are formed. Grain sizes smaller than 60 μm and roundness values of 0˙7 and higher were achieved by 15 s ultrasonic treatment at 623 and 620°C. At higher temperatures, the microstructures are dominantly rosette like and dendritic. At lower temperatures (below 617°C), the samples show inhomogeneous microstructures in terms of grain size and morphology. The current results are useful to set some process parameters for the ultrasonic treatment of liquid Al–Si–Mg foundry alloys prepared for semisolid processing.     

超声波对原位Mg_2Si／Al复合材料中初生Mg_2Si形态的影晌

采用光学显微镜和场发射扫描电镜,研究超声波对原位Mg2Si／A1复合材料中初生Mg_2Si形态的影响。研究结果表明：超声波处理使初生Mg2Si的晶粒尺寸从150μm降低到20μm,初生Mg_2Si形态发生改变。在二维形貌中,未实施超声波振动处理的初生Mg_2Si晶粒生长为含有空腔的粗大颗粒,共晶组织生长于其中,相应的三维形态为含有漏斗状空腔的八面体和十四面体。超声波处理后的初生Mg_2Si晶粒变成细小、实心三维形态的颗粒,颗粒棱角已发生钝化效应。