抽拉速率对一种镍基单晶高温合金凝固组织的影响

研究了抽拉速度对一种镍基高温合金DD98凝固组织的影响。结果发现随着抽拉速率的增加，DD98合金由胞状凝固转变为枝状凝固，γ‘相尺寸变小，由不规则形状逐渐变为规则的立方体形状，γ／γ‘共晶的含量逐渐增加，而共晶中的初生γ‘相尺寸逐渐减小。在胞枝晶转变处存在一次枝晶间距最大值。     

连续电场作用下的铝-铜合金共晶片层形貌

研究了连续电场（包括直流和交流）作用下铝-铜共晶合金凝固组织的形貌。结果表明：经过电场处理后，铝铜共晶合金凝固组织发生了明显的变化；直流电场作用后共晶片层间距经历了一次先减小后增大的过程，并且在较大的电流密度时共晶片层开始发生紊乱；交流电场作用后共晶片层消失，取而代之的是退化共晶组织。     

过共晶铝硅合金凝固组织细化新工艺

综述了过共晶铝硅合金的几种主要细化工艺,重点阐述了高能超声波半固态搅拌法制备过共晶铝硅合金,介绍了高能超声波法的工艺原理和工艺特点,并通过试验证明高能超声波对细化铝硅合金凝固组织具有显著效果。     

稀土合金对高铬铸铁共晶组织及性能的影响

高铬铸铁的韧度与枝晶间共晶碳化物的数量与分布有密切关系。通过定向凝固试样,考察了稀土合金对亚共晶及共晶成分高铬铸铁共晶组织的影响,测定了奥氏体（γ）一次臂的横截面积（Dγ）、共晶区域直径（EW）及碳化物间距（FSC：共晶区域中心碳化物间距;FSC：共晶区域边界碳化物间距）,以及力学性能。结果表明,稀土合金对高铬铸铁共晶组织有明显的细化作用,对其韧度也有一定的贡献。本文还对稀土的作用机理进行了讨论。     

定向凝固条件下Al-2．0%Fe共晶合金中Al3Fe相的生长过程

利用定向凝固技术研究生长速度、合金元素Mn对共晶Al3Fe相生长过程的影响。研究表明：随着生长速度的增加,共晶Al3Fe相将发生由退化共晶向片状→针片状→针状的转变。加入合金元素Mn后,共晶Al3Fe相的形貌由片状、针片状向汉字状、树枝状转变。同时,讨论了各种形貌共晶组织的形成机理。     

定向凝固条件下Al-2.0?共晶合金中Al_3Fe相的生长过程

利用定向凝固技术研究生长速度、合金元素Mn对共晶Al_3Fe相生长过程的影响。研究表明：随着生长速度的增加,共晶Al_3Fe相将发生由退化共晶向片状→针片状→针状的转变。加入合金元素Mn后,共晶Al_3Fe相的形貌由片状、针片状向汉字状、树技状转变。同时,讨论了各种形貌共晶组织的形成机理。     

定向凝固Al-38.5%Cu合金中带状组织的形成机理

在温度梯度为260 K·cm~(-1)和凝固速率为1μm·s~(-1)条件下,对Al-38.5%Cu合金凝固组织中存在的Al_2Cu单相和Al/Al_2Cu共晶相交替生长带状组织的形成机理进行了研究。结果表明:带状组织的产生与合金定向凝固界面前沿的溶质分布有关,形成的原因是合金未达到稳态凝固,凝固速率和合金成分一直处于变化之中;在单相和共晶相的带状组织中,合金凝固速率在单相中随着界面前液相溶质含量的增加而逐渐减小,而在共晶相中随着界面前沿液相溶质含量的增加而逐渐增大。     

定向凝固条件下Al-2．0%Fe共晶合金中Al3Fe相的生长过程

利用定向凝固技术研究生长速度、合金元素Mn对共晶Al     

倾斜板法制备半固态A356合金浆料凝固后的显微组织

采用倾斜板法制备了半固态A356合金浆料,考察了浇注温度、金属液流动距离和冷却板倾斜角度等对其凝固后显微组织的影响。结果表明:倾斜板法通过激冷形核和流动冲击作用,使A356合金中的初生相由枝晶状变为球团状、块状或者蔷薇状的半固态形貌;低的浇注温度、长的金属液流动距离和小的冷却板倾斜角度均有利于形成细小、圆整的初生相,但是也会造成凝固壳的形成或者不均匀组织的倾向增大;适宜的浇注温度为630~640℃、金属液流动距离为800mm、倾斜角度为60°。     

冷却速度对单晶镍基高温合金快速凝固MC碳化物生长形态的影响

本文研究凝固冷却速度对一种镍基单晶高温合金激光表面快速凝固MC碳化物生成形态的影响。发现快速凝固条件下,MC碳化物呈极为特殊的辐射状并随凝固冷却速度和凝固界面形态的变化而显著变化。分析表明,冷却速度对MC碳化物生长形态的影响实质上是冷却速度对共晶反应L→（MC+γ）共晶生长过程影响的结果。     

Effects of Sb,Sr, and Bi on the material properties of cast Al-Si-Cu alloys produced through heated mold continuous casting

Rare earth metals can create a fine eutectic Si structure in cast Al-Si_10.6-Cu_2.5 (ADC12) alloys produced through heated mold continuous casting. Fine and spherical eutectic Si phases are created in the ADC12 alloys through the addition of Sr0.04, and fine lamellar eutectic Si phases are created through Sb and Bi addition. Crystal orientation on the face perpendicular to the casting direction is formed by [110]; however, this uniform formation is collapsed in the ADC12 alloy with an increasing amount of Sr addition, such as Sr > 0.04%. The shape of the eutectic Si is statically analyzed, and the effects of the eutectic Si characteristics on the mechanical properties are examined experimentally. On the one hand, the mechanical properties of the ADC12-Sr alloy increase with increasing Sr content because of the fine eutectic Si, the randomly orientated crystal formation, and so on. On the other hand, the material ductility increases in the ADC12 alloy with increasing addition of Sb and Bi elements. A high fracture strain of approximately 14% is obtained for the ADC12-Bi1.5 alloy.     

Three-Body Abrasive Wear Behavior of Low Carbon Fe–B Cast Alloy and Its Microstructures Under Different Casting Process

This study investigates the effect of semi-solid processing on the microstructures, mechanical properties of low carbon Fe–B cast alloy. The as-cast microstructure of Fe–B cast alloy consists of the eutectic boride, pearlite, and ferrite. Compared with the coarse eutectic borides in the ordinary alloy, the eutectic boride structures in the semi-solid alloy are greatly refined. Moreover, the boride area fraction, Rockwell hardness, impact toughness, etc., before and after heat treatment under different casting methods are also investigated systemically. The wear behaviors of low carbon Fe–B cast alloy are studied by three-body abrasive wear tester. The wear weight loss of semi-solid Fe–B cast alloy is lower than that of the ordinary Fe–B cast alloy because of the lower average boride area for semi-solid specimen. Meanwhile, the wear mechanism of the low carbon Fe–B cast alloy under different casting process is depicted and analyzed by using the physical models.     

Effect of grain refinement and modification on the dry sliding wear behaviour of eutectic Al-Si alloys

The present study deals with an investigation of dry sliding wear behaviour of grain refined and or modified eutectic (Al-12Si) Al-Si alloy by using a Pin-On-Disc machine. The indigenously developed Al-1Ti-3B and Al-10Sr master alloys were used as grain refiner and modifier for the grain refinement of α-Al dendrites and modification of eutectic Si, respectively. Various parameters have been studied such as alloy composition, sliding speed, sliding distance and normal pressure. The cast alloys, master alloys and worn surfaces were characterized by SEM/EDX microanalysis. Results suggest that, the wear resistance of eutectic Al-Si alloys increases with the addition of grain refiner (Al-1Ti-3B) and or modifier (Al-10Sr). Further, the worn surface studies show that adhesive wear was observed in Al-12Si alloy in the absence of grain refiner and modifier. However, an abrasive and oxidative wear was observed when the grain refiner and modifier are added to the same alloy. Commercially available LM-6 (12.5%Si) alloy was used for comparison.     

Effect of Titanium and Nitrogen Additions on the Microstructures and Three-Body Abrasive Wear Behaviors of Fe–B Cast Alloys

This study investigates the effect of titanium and nitrogen elements on the microstructures and wear behaviors of medium carbon Fe–B cast alloy. The as-cast microstructures of Fe–B cast alloy consist of the eutectic boride, pearlite, and ferrite. Moreover, the as-cast eutectic boride structures are greatly refined when titanium and nitrogen are added. The boride area fraction, average boride area, Rockwell hardness, etc., are also investigated systemically. The wear behaviors of medium carbon Fe–B cast alloy are studied by a three-body abrasive wear tester. The results show that the wear weight loss of Fe–B cast alloy with titanium and nitrogen elements is lower than that of the ordinary Fe–B cast alloy. Meanwhile, the wear mechanism of Fe–B cast alloy with different titanium and nitrogen concentrations is described and analyzed.     

内燃机活塞用稀土共晶Al-Si合金中稀土加入量的试验研究

试验从力学性能,线膨胀系数,磨损性能三方面综合研究了稀土加入量对内燃机活塞用共晶Al-Si合金机械性能的影响,对稀土加入量进行了优化,从而使新研制的稀土共晶铝硅活塞合金获得优良的机械性能。     

固溶温度和时间对ZL114A合金组织的影响

通过金相分析、动力学分析等方法,研究了固溶温度和固溶时间对ZL114A合金共晶硅形态的影响。结果表明：固溶温度对共晶硅的粒化过程有很大的影响,在不产生过烧时,温度越高共晶硅的粒化速率越快、粒化程度越彻底;固溶时共晶分枝和凹槽处首先熔断,并且端部钝化逐渐圆整;ZL114A合金在550℃×10h固溶时的硅相形态最为理想。     

均匀化处理对铝锌镁钪合金组织和性能的影响

采用电导率测试、室温拉伸性能测试、扫描电镜和透射电镜分析等方法,研究了不同的均匀化处理对铝锌镁钪合金组织和性能的影响。结果表明:铸态铝锌镁钪合金为过饱和固溶体,合金元素在晶界偏析,形成了富锌、镁的非平衡共晶T相和富铁、硅、锰的杂质相;当均匀化温度为350℃,过饱和基体析出平衡相η-MgZn2;随着均匀化温度的升高,非平衡共晶T相逐渐溶入基体,电导率下降,晶内析出大量Al3(Sc,Zr)粒子,合金的热加工性能提高;470℃×12h是试验合金较适宜的均匀化制度。     

Al-Ti和Al-Ti-C中间合金对消失模铸造AZ91镁合金显微组织的影响

A l-Ti和A l-Ti-C中间合金对消失模铸造AZ91镁合金组织的试验研究表明,与常用变质剂C2C l6相比,加入A l-Ti和A l-Ti-C中间合金对消失模铸造AZ91镁合金具有更好的组织细化效果和更高的力学性能,而加入A l-Ti-C中间合金的作用效果最佳。A l-Ti-C及A l-Ti中间合金的加入提高了共晶反应的离异化程度,晶界上的β相由连续网状变为不连续块状和孤立的粒状结构且分布均匀。A l-Ti-C中间合金对消失模铸造AZ91镁合金晶粒细化是其晶粒生长抑制作用和引入形核质点综合作用的结果。