铝合金液浸蚀对H13钢焊合表面的影响

将H13钢在680 ℃热铝合金液中浸蚀1、3和5 h后,对其形成的焊合表面的形貌、厚度和成分进行研究。结果表明,随着浸蚀时间的延长,表面从局部腐蚀扩展为全面腐蚀,表面过渡层平均厚度逐渐增加,5 h后厚度达到106 μm。随着与钢基体的距离增大,焊合表面Fe含量逐渐减少,Al含量逐渐增加,Fe、Al原子相互扩散生成金属间化合物层。     

H13钢铝合金压铸模开裂原因分析

电镜及金相检验结果分析表明，由于压铸模模具的成分偏析而产生由马氏体及残留奥氏体构成的带状组织缺陷，工作时模具表面出现回火裂纹，在内应力作用下模具发生早期热疲劳破坏。     

H13钢铝合金压铸模的失效分析

用光谱分析仪、硬度计、金相显微镜对深圳、重庆、厦门模具厂的3种H13钢铝合金压铸模进行检测和失效分析.结果表明,失效的原因是这些钢中共晶碳化物等偏析较严重,导致其早期失效.     

稀土元素变质A356铝合金的研究进展

总结了目前国内外采用稀土对A356铝合金变质的研究进展,归纳了稀土元素对A356铝合金的变质效果。综合目前的研究结果,结合商业化A356铝合金应用的实际情况,认为采用DOE成分设计方法对相对价廉的二元、甚至多元稀土或稀土与其他元素的复合变质体系进行成分设计是有前景且符合实际的。     

H13钢铝合金压铸模的离子氮化

采用加氩渗氮和无氩渗氮两种离子渗氮方法,对用作铝合金压铸模材料的H13钢的热疲劳性能进行了比较.结果发现,无氩渗氮的化合物层对H13钢的热疲劳性能具有双重影响,一方面能推迟热疲劳裂纹的萌生,阻止热裂纹向基体内部扩展,另一方面表面裂纹直、宽、多,易于剥落并扩展快,因此,采用含化合物层的离子氮化处理H13钢铝合金压铸模应该慎重.     

H13模具钢铝合金工件生产应用现状综述

介绍了H13钢模具在铝合金工件生产上损坏的原因,H13中碳化物的尺寸、分布以及形貌对寿命的影响和合金化元素对模具性能的影响。综述了H13各种热处理工艺以及表面处理的方法及其对H13模具使用寿命的影响,以期促进这些工艺的应用和发展。     

H13钢穿孔顶头的稀土铝合金化研究

对H13钢穿孔顶头进行了稀土、铝合金化研究。经分析表明,稀土铝合金化可以明显改善H13钢顶头的铸造性能,消除中心缩孔现象,并细化晶粒和碳化物,降低S、P含量。经现场穿管试验,稀土铝合金化后的H13钢顶头的使用寿命比原H13钢顶头提高40％。     

流变模锻A356铝合金的显微组织和力学性能

采用机械搅拌法制备A356合金半固态浆料,在200 t油压机上进行流变模锻成形,研究了流变模锻试样热处理前后的组织和力学性能.结果表明:流变模锻试样组织由球形α-Al晶粒和α+Si共晶组织组成;热处理前试样抗拉强度为261.7 MPa,伸长率为4.1％;经T6热处理后,试样抗拉强度为347.8 MPa,提高了32.9％...     

H—13钢材料和热处理规范

本文介绍了通用汽车公司用于铝压铸模的热作工具钢的规范，尤其对材料的实验室检测程序进行了详细的描述。表明，当冲击韧性值小于8.1Nm时，大型型芯100％会发生裂纹引起失效。8.1-10.9Nm是一个转折区域。大于10.9Nm时裂纹失效很少，当型芯的材料及热处理满足规定要求时，刑芯寿命可达到20万次左右。     

Evolution of microstructure and mechanical properties of A356 aluminium alloy processed by hot spinning process

The evolution of microstructure and mechanical properties of A356 aluminum alloy subjected to hot spinning process has been investigated.The results indicated that the deformation process homogenized microstructure and improved mechanical properties of the A356 aluminum alloy.During the hot spinning process,eutectic Si particles and Fe-rich phases were fragmented,and porosities were eliminated.In addition,recrystallization of Al matrix and precipitation of AlSiTi phases occurred.The mechanical property testing results indicated that there was a significant increase of ductility and a decrease of average microhardness in deformed alloy over die-cast alloy.This is attributed to uniform distribution of finer spherical eutectic Si particles,the elimination of casting defects and to the recrystallized finer grain structure.     

Taper barrel rheomoulding process for semi-solid slurry preparation and microstructure evolution of A356 aluminum alloy

The self-developed taper barrel rheomoulding (TBR) machine for light alloy semi-solid slurry preparation was introduced. The semi-solid slurry was obtained from the intense shearing turbulence of the alloy melt in the cause of solidification, which was further caused by the relative rotation of the internal and external taper barrel whose surface contained wale and groove. The heat transmission model of TBR process, the flow rules and the shearing model of the alloy melt were deduced. Taking A365 as experimental material, the microstructure evolution rules under different slurry preparation processes were analyzed. The results show that decreasing the pouring temperature of A365 alloy melt properly or increasing the shearing rate helps to obtain ideal semi-solid microstructure with the primary particle size of about 70 μm and the shape factor of above 0.8.     

A356铸造铝合金的疲劳裂纹萌生及短裂纹扩展研究

研究了A356-T6铸造铝合金的缺口疲劳裂纹萌生与早期扩展行为及机制.结果表明,热等静压试样的疲劳抗力优于非热等静压试样.对于钝缺口试样,疲劳裂纹萌生于缺口根部附近的多个平面,最终哪个裂纹源扩展成主裂纹取决于局部微观组织.对于缺口几何形状不同的热等静压和非热等静压疲劳试样,在疲劳过程中,不管是在高应力状态下,还是在低应力状态下,都出现了铝基体的循环塑性变形和共晶硅粒子断裂导致疲劳裂纹萌生.对于非热等静压试样,铸造缩孔在构件的疲劳过程中起着重要作用,但即使缺口根部存在较大尺度的铸造缩孔,导致了疲劳裂纹萌生,但也同时观察到疲劳裂纹从共晶硅粒子、金属间化合物、铝基体的滑移带和铁基金属间化合物等处萌生.对于脆性的A356铸造铝合金可采用修正的断裂力学参量ΔKn、局部应力范围Δσ或局部应变幅Δε/2作为控制参量来表征疲劳裂纹萌生行为,而缺口有效应力强度因子范围ΔKneff和ΔJs参量可用来表征缺口场中短裂纹扩展行为.     

Computer-aided cooling curve analysis of A356 aluminum alloy

Computer aided cooling curve analysis (CA-CCA) is very useful in the foundry industry for easy and fast evaluation of a variety of properties. Typical applications include the prediction of the temperatures and amounts of different phases appearing during solidification and monitoring of the quality of melt in terms of Si- modification, grain refinement, inoculation, and graphite spheoridization. The use of cooling curve analysis can be extended to many other areas of solidification also, assuming the calculated values are reasonably accurate. The calculation of zero curve, which is vital in cooling curve analysis, offers many problems however. In this study, an attempt was made to investigate the problems of zero curve calculation and a new method is suggested to minimize calculation errors. An in-house developed computer program was used for a complete analysis of aluminum alloy A356 to determine the latent heat and solid fraction values.     

A356铝合金微弧氧化膜微动磨损行为的研究

采用微弧氧化（MAO）在A356铝合金表面制备MAO膜,利用球-平面接触在SRV-V微动摩擦磨损机上探究变载荷和位移下微弧氧化对A356微动磨损机理的影响。结果表明：MAO膜由疏松层和致密层构成,其均匀性、致密性和结合力良好。MAO膜的摩擦系数、磨损率均低于A356,MAO膜减摩耐磨性较好。随位移增加MAO膜的摩擦耗散能系数低于A356,MAO膜能提升A356微动磨损过程的稳定性。载荷增加时A356磨损机制为磨粒磨损-粘着磨损,伴随犁削和疲劳剥层; MAO膜磨损机制为磨粒磨损-粘着磨损和疲劳剥落。位移增加时A356磨损机制为粘着磨损和疲劳剥落,伴随微犁削;MAO膜磨损机制为粘着磨损和疲劳剥层-粘着磨损和磨粒磨损。A356的磨痕内聚集Fe、O元素,存在材料转移和氧化磨损;MAO膜磨痕内聚集Fe元素,存在材料转移。     

Simulation of cooling channel rheocasting process of A356 aluminum alloy using three-phase volume averaging model

The cooling channel process is a rehocasting method by which the prematerial with globular microstructure can be produced to fit the thixocasting process. A three-phase model based on volume averaging approach is proposed to simulate the cooling channel process of A356 Aluminum alloy. The three phases are liquid, solid and air respectively and treated as separated and interacting continua, sharing a single pressure field. The mass, momentum, enthalpy transport equations for each phase are solved. The developed model can predict the evolution of liquid, solid and air fraction as well as the distribution of grain density and grain size. The effect of pouring temperature on the grain density, grain size and solid fraction is analyzed in detail.     

Rheo-squeeze casting of semi-solid A356 aluminum alloy slurry

The effect of pouring temperature, electromagnetic stirring power and holding process on semi-solid A356 aluminum alloy slurry was investigated, then the slurry was squeeze-cast. The results show that when the pouring temperatures are properly above the liquidus line, for example 630-650 °C, the slurry with spherical primary α(Al) grains can be prepared under the stirring power of 1.27 kW. The slurry is then homogeneously held for a short time, and the primary α(Al) grains are further ripened and distributed evenly in the slurry. The results of the rheo-squeezed casting experiments show that the injection specific pressure has a great effect on the filling ability of the semi-solid A356 aluminum alloy slurry, and the higher the injection specific pressure is, the better the ability for the slurry to fill the mould cavity is. When the injection specific pressure is equal to or above 34 MPa, the whole and compact rheo-squeezed castings can be obtained. The microstructure of the castings indicates that the shape, size and numbers of the primary α(Al) grains in different parts of the castings are highly consistent. After being held at 535 °C for 5 h and then aged at 155 °C for 12 h, the ultimate strength of the rheo-squeezed castings can reach 300-320 MPa, the yield strength 230-255 MPa, and the elongation 11%-15%.     

Mn/Fe摩尔比对A356铸造铝合金富铁相形态的影响

在含1.0%Fe(质量分数)的A356铝合金中添加不同含量的Mn,采用OM、SEM、EDS及DSC等分析方法研究Mn/Fe摩尔比对富铁相形态的影响及其规律,探讨添加Mn后A356-1.0Fe合金中物相的凝固顺序。结果表明:随着Mn/Fe摩尔比的提高,富铁相形态的演变顺序为:针状→汉字状→树枝状→星形→多边形状,当Mn/Fe摩尔比超过1.2时可基本消除针状铁相。富铁相中(Fe,Mn)/Si摩尔比随富铁相形态的凝固先后顺序逐渐增加,分别为针状富铁相中(Fe,Mn)/Si摩尔比为0.5~0.7,树枝状和汉字状富铁相中(Fe,Mn)/Si摩尔比为的1.2~1.7,星型和多边形富铁相中(Fe,Mn)/Si摩尔比为1.9。富铁相的平均晶粒尺寸和体积分数随Mn/Fe摩尔比的增加先增加后减小,而后再增加。其中当Mn/Fe摩尔比为1.0时,富铁相的平均晶粒尺寸和体积分数均为最小,与A356-1.0Fe合金的相近。此外,Mn的添加有利于提高共晶相和α(Al)基体相的形成温度,有利于多边形富铁相的形成。