Zesheng JI
,
Maoliang HU
,
Xiaoping ZHENG
材料科学技术（英文）
To investigate the thixotropic fluidities, microstructures and mechanical properties of semi-solid AZ91D magnesium alloy during reheating, a self-made die set with channels of different sizes were used. The results show that critical forming forces and maximal forming forces could be obtained and related to the holding times in the semi-solid forming process. In the holding time of 0-2700 s, with increasing the holding time, maximal forming force decreased sharply and critical forming force decreased slowly. In the whole thixotropic flowing process, the filling-in was steady and the surface fineness was good. The forming force increased when the slurry changed the flowing direction or flowed from the big-diameter chamber to the small-diameter one. The tensile strength and elongation to failure of the sample after holding time for 2700 s, compared to as-cast sample, are increased by approximately 42.7% and 180%, respectively, and the fractured surfaces presented dimple-like pattern.
关键词:
AZ91D magnesium alloy
,
magnesium
,
alloy
,
semi-solid
,
thixot
Weimin MAO
材料科学技术（英文）
The effects of pouring temperature, short electromagnetic stirring with low strength and then soaking treatment on the microstructure of AlSi7Mg alloy were investigated. The results show that if AlSi7Mg alloy is poured at 630 or 650℃ and meanwhile stirred by an electromagnetic field at a low power for a short time, the pouring process can be easily controlled and most solidified primary α-Al grains become spherical and only a few of them are rosette-like. Weak electromagnetic stirring makes the temperature field more homogeneous and makes the primary α-Al grains disperse in a larger region, which leads to the spherical microstructures of primary α-Al grains. When the AlSi7Mg alloy is soaked or reheated at the semisolid state, the primary α-Al grains ripen further and they become more spherical, which is favorable to the semi-solid forming of AlSi7Mg alloy.
关键词:
AlSi7Mg alloy
,
alloy
,
semi-solid
,
pouring
,
tempera
Z. Liu
,
W.M. Mao
金属学报(英文版)
The semi-solid slurry of A356 alloy, which is grain-refined by Al-Ti-B master alloy, is prepared by low superheat pouring and slightly electromagnetic stirring. The effects of grain-refine on the morphology and the grain size of the primary α phase in the slurry manufactured are researched. The results indicate that the slurry with particle-like and rosette-like primary α phases can be prepared by low superheat pouring and slightly electromagnetic stirring from liquid A356 alloy grain-refined, in which the pouring temperature can be suitably raised. Compared with the A356 samples without grain-refined, the grain size and particle morphology of primary α phase as well as the distribution of the grain with particle-like or rosette-like along radial in the ingot in A356 are markedly improved by grain-refined.
关键词:
semi-solid
,
null
,
null
,
null
,
null
,
null
W.M. Mao
,
A.M. Zhao
,
X.Y. Zhong
金属学报(英文版)
The nondendritic semi-solid slurry preparation of high chromium cast iron Cr20Mo2
has been studied in this paper. The experiments show that the proeutectic austenitic
particles are more spherical under a larger stirring power condition, even if the stirring
time is shorter, while the proeutectic austenitic particles are not very much spherical
under a smaller stirring power condition and some proeutectic austenitic dendrites
also exist, even if the stirring time is very long. The experiments also show that when
stirred for 5{6 minutes under the test condition, the semi-solid slurry with 40vol.%{
50vol.% solid fraction and spherical proeutectic austenite in the size of 50{80¹m can
be obtained.
关键词:
high chromium cast iron
,
null
,
null
陈永楠
,
张学敏
,
魏建锋
,
赵永庆
稀有金属材料与工程
通过模拟镦锻压缩和模锻实验研究Ti14合金半固态下的触变锻造特性,分析了锻造过程中的组织演变过程,测定了锻件的力学性能,并综合讨论了该合金半固态下的触变可锻性.结果表明:Ti14合金在半固态较常规固相下具有较小的镦锻变形抗力;其中,1000到1100℃之间触变镦锻变形量可达70％～85％.半固态模锻结果表明:1000和1050℃下,合金在变形量为45％～75％时表现出良好的可锻性,锻件表面无明显缺陷.分析认为:由于液相的协调变形机制,半固态下触变模锻较常规模锻,减少了晶界处的应力集中,有效降低了合金的变形抗力;同时,触变锻造可以有效细化晶粒,提高力学性能,改善合金的成形性.
关键词:
半固态
,
钛合金
,
触变锻造
,
微观组织
,
力学性能
刘旭波
,
赵丽
,
郭洪民
,
叶寒
材料导报
介绍了材料智能处理与制造(IPMM)的概念,结合半固态成形技术特点,分析了材料智能处理在金属半固态成形技术中的应用结合点,从材料成形的模拟仿真预测、工艺过程的智能控制、智能传感器的研究和控制方法等方面提出了金属半固态成形技术智能处理的研究方向.
关键词:
IPMM
,
半固态
,
模拟仿真
,
智能控制
,
传感器
胡永俊
,
李昔强
,
李风
,
郑辉庭
,
李人杰
功能材料
doi:10.3969/j.issn.1001-9731.2015.06.023
在150℃下对半固态亚共晶 Sn-52Bi 浆料分别进行5,10和15 min 的机械搅拌,采用真空吸铸水冷制备出半固态Sn-Bi合金,测试了半固态Sn-Bi合金的组织、力学与热性能,研究剪切力对半固态浆料组织演变的影响,探索半固态合金延伸率与熔化潜热的关系.结果表明：对 Sn-52 Bi 半固态浆料进行机械搅拌,剪切力可抑制树枝状初生 Sn 相的形成,真空吸铸水冷得到的合金组织由非树枝状的初生 Sn 相和共晶体构成；随着搅拌时间的延长,短锤状初生 Sn 相转变为直径约20μm的近球状,搅拌时间延长至15 min时球状初生Sn相直径变小但出现团聚.当搅拌速度为320 r/min,机械搅拌时间为10 min 工艺得到半固态Sn-Bi合金延伸率为46．75％,与180℃下的合金熔液直接水冷凝固相比提高了160％；差式扫描量热分析(DSC)得出：不同机械搅拌时间半固态 Sn-52 Bi 合金的峰值温度为140℃,随着合金延伸率升高,合金的熔化潜热减小.
关键词:
半固态
,
机械搅拌
,
微观组织
,
延伸率
,
熔化潜热
索江龙
,
李元东
,
何明涛
,
胡韶华
,
陈体军
,
马颖
材料热处理学报
采用光学显微镜(0M)、扫描电镜(SEM)、X射线衍射仪(XRD),研究了固溶处理对流变压铸2024变形铝合金组织及硬度的影响.结果表明,流变压铸成形的2024变形铝合金在495℃固溶处理12 h后,共晶相θ(CuAl2)相和S(CuAl2Mg)相逐渐固溶进入α-Al基体内部,使得合金基体中的过饱和Cu、Mg合金元素的含量增多,对合金起到良好的固溶强化作用.而且,随着固溶时间的增加,流变压铸成形2024的组织中的初生颗粒与二次凝固区颗粒出现合并长大现象,其它们的长大速率都随固溶时间的延长而降低.
关键词:
2024变形铝合金
,
半固态
,
流变压铸
,
固溶
李亚庚
,
毛卫民
,
朱文志
,
杨斌
,
朱达平
中国有色金属学报
通过差示扫描量热法确定半固态7075铝合金温度与固相分数的关系，采用Couette型同轴双筒流变仪研究连续冷却状态下半固态7075铝合金浆料的表观黏度及其影响因素。结果表明：在连续冷却条件下，当剪切速率(γ?)不变时，冷却速率(v)越大，半固态7075铝合金浆料的表观黏度(ηa )越大；当冷却速率一定时，剪切速率越大，相同温度时半固态7075铝合金浆料的表观黏度越小。对半固态7075铝合金浆料的表观黏度与冷却速率、剪切速率及固相分数(f s )的关系进行数值拟合，为半固态7075铝合金成形的计算机模拟提供了依据：当剪切速率=61.235 s-1时，ηa =(0.21+0.18v)exp(3.99 fs)；当冷却速率v=4℃/min时，ηa =2.23exp(3.87γ?)exp(-0.01fs)。γ?
关键词:
7075铝合金
,
半固态
,
连续冷却
,
表观黏度
周冰
,
康永林
,
郜俊震
,
祁明凡
,
张欢欢
中国有色金属学报
采用自主研发的强制对流搅拌装置(FCR)，研究筒体温度、浇注温度和搅拌速度对A356铝合金半固态组织的影响规律，探讨半固态浆料制备过程中的凝固行为。结果表明：适当降低浇注温度、筒体温度和提高搅拌速度均有利于半固态浆料组织的改善，能够制备晶粒细小、圆整、分布均匀的半固态组织；当浇注温度为620~630℃、筒体温度为570~580℃、筒体转速为200 r/min以上时，均能获得理想的半固态浆料，其初生固相颗粒平均直径在80μm以下，形状因子在0.75以上；强制对流搅拌装置极大地改变了传统凝固条件下熔体依靠传导单向传热和扩散缓慢传质的状态，使熔体的温度场和成分场趋于一致，破坏了枝晶生长的条件，有利于获得较好的半固态组织。
关键词:
A356铝合金
,
半固态
,
强制对流
,
流变成形
,
组织演变
