熔体过热处理对铝基合金非晶形成能力的影响

利用熔体粘度测试、X射线衍射分析、高温DSC分析等方法,研究了Al84Mg10Ce6合金的熔体粘度随温度变化的规律,结合薄带的非晶形成能力,分析了合金熔体不同过热温度与其非晶形成能力的相关性.结果表明,Ce元素的加入使得Al84Mg10Ce6熔体产生了结构突变,增强了铝基合金非晶形成能力,Al-Mg系合金非晶形成能力与其熔体温度之间具有相关性,850 ℃熔体通过熔甩工艺制得非晶态薄带.     

Al—Cu共晶合金熔体中稀土Ce与氢的相互作用

研究了不同稀土Ce含量对共晶成分Al-33.2Cu (质量分数,％,下同）熔体氢含量的影响。结果表明：在相同的保温时间和保温温度条件下,稀土的加入增加了合金熔体的氢含量。750℃,保温20min,加入0．6的Ce,Al-Cu共晶合金熔体的氢含量由0．06mL/100g增至0．16mL/100g。研究了不同Ce含量Al-Cu共晶合金熔体氢含量随温度变化的规律。实验 温度分别为720℃,750℃,800℃和850℃,含0．6Ce的Al-Cu共晶合金熔体氢含量的值分别为0．14、0．16、0．23和0．29mL/100g。     

Mg、Si对Al熔体中氢含量及氩气除气效果的影响

研究了合金元素Mg、Si对Al熔体中的氢含量及氩气除气效果的影响。结果表明，Mg、Si元素均明显增强了Al熔体的吸气倾向。在Mg元素单独存在时，熔体中的氢含量随Mg含量的增加而上升，氩气除气效果也逐渐明显，但除气后，熔体中的氢含量仍较高；Si的加入能阻碍Al熔体中的氢原子向氩气气泡的扩散，因而，明显降低了氩气除气的效果；Mg、Si元素共存不仅增加了铝合金熔体的吸氢倾向，而且增加了除气的难度，但短时间除气仍有一定效果。     

微量TiC、TiB2引起铝熔体粘度的突变现象

研究了TiC、TiB2两种钛化物对纯铝及亚共晶Al 6 5%Si合金熔体粘度的影响。结果表明,加入少量Al 5Ti 1B或Al 3Ti 0 15C中间合金的铝熔体,其粘度大幅度增加。如在工业纯铝中加入0 3%的Al 5Ti 1B后,其粘度增加了31 83%;在Al 6 5%Si合金熔体中加入0 5%的Al 3Ti 0 15C后,其粘度增加了59 51%。因此,熔体中引入固相粒子是引起熔体粘度增加的原因之一,并在此基础上进行了机理探讨。     

Al-5Ti-xCe细化剂制备及对Al-7Si合金组织和冲击性能的改善

试验研究了铈含量对细化剂Al-5Ti-x Ce(x分别为0.3,0.6,0.9)微观组织的影响,以及细化剂Al-5Ti-x Ce对Al-7Si合金组织和冲击性能的影响。结果表明,稀土Ce加入到Al-5Ti合金后,合金基体中的Al3Ti的尺寸明显降低,Al3Ti形状由长条状转变为羽毛状,并随着稀土Ce添加量增加,Al3Ti尺寸进一步降低,当Ce的加入量(质量分数,下同)为0.6%时,Al3Ti尺寸降低至最小,当Ce的添加量增至0.9%时,Al3Ti尺寸不再细化;用不同Ce的添加量的Al-5Ti-x Ce细化剂细化Al-7Si合金,发现随着Al-5Ti-x Ce中Ce的添加量增加,Al-7Si合金中α-Al树枝晶逐渐细化,其中Al-5Ti-0.6Ce细化剂的细化效果最佳;随着Al-5Ti-x Ce中Ce的添加量增加,Al-7Si合金中粗片状的共晶硅逐渐变得细小,其冲击性能随Al-5Ti-x Ce细化剂中铈含量的增加而显著提升,当Al-5Ti-x Ce中Ce的添加量增加到0.9%时,冲击性能不再增加。     

合金化对AZ91D镁合金组织与力学性能的影响

利用光学显微镜（OM）和X射线衍射（XRD）分析了分别加入合金化元素Ce，Si和Ca后AZ91D合金的铸态组织和相组成，测试了合金室温拉伸性能和硬度。结果表明：加入Ce和Si后合金组织中分别生成杆状Al4Ce和汉字状Mg2Si相，而加入Ca后无新相生成，加入的Ca主要固溶于β相中；Al4Ce和Mg2Si相在合金凝固过程中被推移到生长界面，Ca原子偏聚在生长界面前沿，从而阻碍枝晶的自由生长，细化合金铸态组织：Ce和Ca的加入可提高合金室温综合力学性能，且前者提高程度要高于后者提高程度，而Si的加入却降低合金室温综合力学性能。     

Al-P中间合金对共晶和过共晶Al-Si合金的变质机制

探讨了Al—P中间合金对共晶及过共晶Al—Si合金的变质特点，P在Si相中的存在形式、分布规律及变质机制．实验表明，Al—P中间合金可有效地细化过共晶Al—Si合金中的初晶Si，使该合金的σb．20℃和δ20℃分别提高19．0％和125％．对共晶型Al—Si合金而言，Al—P中间合金可促使析出细小的初晶Si，获得过共晶型组织，并将针片状的共晶Si变为短杆状，从而使该材料的σb，20℃和σb，300℃分别提高11．1％和18．9％．Al—P中间合金加入到过共晶Al—Si合金中，P主要以AlP形式存在于初晶Si内部；加入到共晶Al—Si合金中的P分别以AlP和原子态P存在于Si相内．P对过共晶Al—Si合金变质是以AlP异质形核机理为主；而P对共晶Al—Si合金的变质是以AlP异质形核和原子态P影响Si相形态两种机制共同作用的结果．     

Sn在651合金中存在的形式和对性能的影响

前言研究表明,Sn对Al—Mg—Si系合金效时特性有明显的影响。Sn明显地延长了Al—Mg—Si合金淬火后室温时效的孕育期,延长的程度随Sn含量的增加而增加。加入Sn降低了人工时效后的硬度。为了解释这些现象,必须研究Sn以什么样的形式存在于Al—Mg—Si合金中。本试验主要用电子探针方法配合电阻率的测定对Sn的存在形式进行了研究。     

Ce—P对过共晶铝硅合金的双重变质作用

研究了P、Ce及其复合加入对过共晶Al－20％Si合金的变质作用,对变质效果进行了综合比较。结果表明,P、Ce复合变质能同时细化初晶Si和共晶Si,且变质效果能持续5h。     

Ce对Mg-Li-Al合金组织及力学性能的影响

研究了Ce对Mg-16Li-5Al合金铸态组织及力学性能的影响。结果表明,加入Ce后,晶粒细化,随稀土化合物Al2Ce的增加,Mg17Al12、AlLi两相减少;Ce的加入提高了合金的强度和耐热性能,大量Al2Ce的存在,易割裂基体,使强度降低;分布在晶界附近的稀土化合物改变了合金的断裂方式。     

三元液态合金Al85Ni10M5的比热容

利用差示扫描量热仪测定了三元液态合金Al85Ni10M5(添加元素M包括Si，Mn，Ti和Ce)的比热容。结果表明：在高温处Al85Ni10M5液态合金的比热容曲线上均有驼峰出现，其位置随添加元素的原子半径的增大和电负性的减小而向高温处偏移。而且更高温度处，比热容值出现线性下降趋势。液态合金比热容的变化规律充分说明了液态合金中具有微观组织的不均匀性。     

Effect of Sr modification on microstructure and thermal conductivity of hypoeutectic Al−Si alloys

Trace amount of Sr (0.05 wt.%) was added into the hypoeutectic Al−Si (3−12 wt.% Si) alloys to modify their microstructure and improve thermal conductivity. The results showed that the thermal conductivity of hypoeutectic Al−Si alloys was improved by Sr modification, and the increment and increasing rate of the thermal conductivity gradually increased with Si content increasing. The improvement of thermal conductivity was primarily related to the morphology variation of eutectic Si phases. In Sr-modified Al−Si alloys, the morphology of eutectic Si phases was a mixed morphology of fiber structure and fine flaky structure, and the proportion of the fine flaky eutectic Si phases gradually decreased with Si content increasing. Under the Si content reaching 9 wt.%, the proportion of fine flaky eutectic Si phases was nearly negligible in Sr-modified alloys. Correspondingly, the increment and increasing rate of thermal conductivity of Sr-modified alloys reached the maximum and tended to be stable.     

INFLUENCES OF TRACE ADDITIONS OF STRONTIUM AND PHOSPHORUS ON ELECTRICAL RESISTIVITY AND VISCOSITY OF LIQUID Al-Si ALLOYS

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The dynamic viscosity of liquid Cu–Si alloys

The dynamic viscosity of liquid Cu–Si alloys is measured in the Cu-rich composition range (up to 40 at.% Si). The Arrhenius-law describing the temperature dependence of the viscosity holds for all alloys investigated. The viscosity isotherms, both experimental and from thermodynamic model calculations, show a broad maximum covering the homogenity ranges of the intermetallic phases. An interconnection of such findings with the atomic structure of the liquid alloys is briefly discussed.     

Viscosity variation of hypereutectic Al–Si alloys with high iron contents around liquidus temperature

The viscosity of high Fe-containing hypereutectic Al–Si alloys was studied by using a high-temperature Searle-type rheometer. The results show that the steady-state viscosity of Al–17Si–(2,3,4) Fe alloy melts increases with the increase of iron content. During the continuous cooling of Al–17Si–(2,3,4) Fe alloy melts, the transient viscosity increases slowly at the initial stage of cooling. When the temperature decreases to a critical value, the transient viscosity increases abruptly. In the cooling process of Al–17Si–2Fe–(0,0.4,0.8)Mn alloy melts, the steady-state viscosity continues to increase and reach the maximum value firstly, then decreases abruptly, and then continues to increase again. The steady-state viscosity of Al–17Si–2Fe, Al–17Si–2Fe–0.4Mn and Al–17Si–2Fe–0.8Mn alloy melts experiences a sudden decrease at 630°C, 640°C and 670°C respectively due to the settlement of Fe-rich phases. The maximum value of viscosity of the Al–17Si–2Fe–(0,0.4,0.8)Mn alloy melts is increased with the increase of Mn content.     

Effect of Silicon on the Thixoformability of Al-Si-Cu Alloys

The thixoformability of new Al-Si-Cu alloys was evaluated and characterized by their microstructural and rheological behavior. Alloys Al1Si2.6Cu, Al2Si2.6Cu, Al4Si2.6Cu, and Al7Si2.6Cu were produced with the addition of Al5Ti1B grain refiner alloy. The materials were heat treated under two controlled conditions: holding times of 0, 30, 90, and 210 s and solid fraction of 45 and 60%. The evaluation of the microstructure and semisolid behavior was characterized by globule size, shape factor (SF), minimum stress to flow, maximum stress, and apparent viscosity. The heat treatment times promoted the globularization of solid phase particles to achieve better apparent viscosity results for the alloys treated for 210 s. Both 45 and 60% solid fraction showed no significant differences in terms of SF, but the alloys containing lower solid fraction showed better performance for apparent viscosity. Better working ranges for these new Al-Si-Cu alloys were determined reaching average strain of 0.5 MPa and apparent viscosity of 10⁵ Pa s.     

Co41Ni32Al27-xSix合金的马氏体相变和磁性转变

利用金相显微组织分析技术、示差扫描量热法(DSC)和振动磁力计(VSM),考察了Co41Ni32Al27-xSix合金中Si元素含量x对马氏体相变和铁磁性转变的影响,用X射线衍射方法分析马氏体相的结构类型.增加x能够显著提高合金的马氏体相变温度,并且同时提高铁磁性转变Curie点;在x≤5的范围内,x增加1可以造成马氏体相变温度提高50-60 K,同时Curie点提高大约10 K;马氏体相的晶体结构仍然是L10型有序结构,但是随着x的增加,单胞体积减小.讨论了马氏体相变温度和Curie点同时提高的原因.     

Stability of amorphous Al90TMxCe10—x（TM=Fe or Ni） alloys

X-ray diffraction(XRD) and differential scanning calorimetry(DSC) were used to investigate the crystallization process of amorphous Al90TMxCe10-x (atom fraction in%;TM=Fe or Ni;x=3,5)alloys,Aging effects were examined by X-ray diffraction,The structure corresponding to the prepeak for the amorphous Al90Fe5Ce5 alloy is more stble than the amorphous matrix,but it is not stable for amorphous Al90Ni5Ce5 alloy during the first crystallization stage and even decomposes at room temperature,Although both Al-Ni and Al-Fe have strong chemical bonding,the cyrstallization onset temperature of amorphous Al-Fe-Ce alloys is much higher than that of amorphous Al-Ni-Ce alloys,which is likely caused by the different stability of the structure corresponding to the prepeak.The crystallization onset temperature increases as Ce/Ni ratio increases in amporphous Al90NixCe10-x alloys,whereas it decreases as Ce/Fe ratio increases in amorphous Al90FexCe10-x alloys.A better atomic packing produces as Ce content increases because of the size mismatch in Al-Ni-Ce systems and as Fe content increases because of the increasing Fe central structural units.     

Ce含量对Mg-Li-Al-Zn合金显微组织和拉伸性能的影响(英文)

制备了Mg-5Li-3Al-2Zn-xCe(x=0-2.5;质量分数,%)铸态合金,并将所得合金分别于300°C和370°C进行均匀化和固溶处理;研究固溶处理后合金显微组织和拉伸性能的变化。结果表明,合金中加入Ce后出现Al2Ce/Al3Ce析出相,此时合金主要由α-Mg、Al2Ce、Al3Ce和AlLi相组成;固溶处理后合金中AlLi和Al-Ce析出相数量减少。析出相的数量与形态对合金的力学性能十分重要,含有1.0%Ce的合金获得了优良的拉伸性能。固溶处理后Mg-5Li-3Al-2Zn-0.5Ce合金的强度和伸长率都得到了大幅度的提高,这是因为合金在固溶处理后由于基体中的溶质原子增加而获得良好的固溶强化作用。     

Influence of Silicon and Aluminum Additions on the Oxidation Resistance of a Lean-Chromium Stainless Steel

The effect of Si and Al additions on the oxidation of austenitic stainless steels with a baseline composition of Fe–16Cr–16Ni–2Mn–1Mo (wt.%) has been studied. The combined Si and Al content of the alloys did not exceed 5 wt.%. Cyclic-oxidation tests were carried out in air at 700 and 800°C for a duration of 1000 hr. For comparison, conventional 18Cr–8Ni type-304 stainless steel specimens were also tested. The results showed that at 700°C, alloys containing Al and Si, and alloys with only Si additions showed weight gains about one half that of the conventional type-304 alloy. At 800°C, alloys that contained both Al and Si additions showed weight gains approximately two times greater than the type-304 alloy. However, alloys containing only Si additions showed weight gains four times less than the 304 stainless. Further, alloys with only Si additions preoxidized at 800°C, showed zero weight gain in subsequent testing for 1000 hr at 700°C. Clearly, the oxide-scale formation and rate-controlling mechanisms in the alloys with combined Si and Al additions at 800°C were different than the alloys with Si only. ESCA, SEM, and a bromide-etching technique were used to analyze the chemistry of the oxide films and the oxide–base-metal interface, in order to study the different oxide film-formation mechanisms in these alloys.