张静华
,
唐亚俊
,
张志亚
,
于洋
,
张济山
,
李英敖
,
胡壮麒
材料研究学报
本文研究一种在热腐蚀环境下工作的Ni 基单晶高温合金错配度以及γ′筏状形成与性能的关系;通过蠕变和持久试验,研究合金的变形组织和强化特点。在变形过程中,基体运动位错遇γ′相受阻而在γ′相表面形成位错网络,这种位错结构在变形中形成了新的强化机制,提高了合金的蠕变抗力。
关键词:
Ni基高温合金
,
single crystal alloy
,
dislocation structure
,
strengthening mechanism
米国发
,
浮红霞
,
刘彦磊
,
田世藩
稀有金属材料与工程
利用多功能雾化沉积装置,制备了Ni3Al-Mo高温合金.拉伸性能测试表明:喷射沉积Ni3Al-Mo合金的屈服强度有明显的"R"特性,即喷射沉积合金的屈服强度随着温度的增加而增加,在760 ℃时达到最大值;随着温度的继续增加,屈服强度会逐渐降低.利用TEM对位错结构分析,阐明了合金屈服强度与微观结构之间的关系.研究结果表明,试验合金所具有的屈服强度随温度的变化规律主要是由不同温度下γ′及γ相内的位错缠结状况、位错对的形态及数量和六面体滑移系的开动程度决定的.裂纹的TEM分析表明,随着变形应力的增加,裂纹在晶界部位产生,然后迅速扩展,而且在不同的晶面内存在一些不同的滑移带.喷射沉积合金在室温、中温及高温下裂纹严格沿八面体滑移系(111)面开裂.
关键词:
Ni3Al-Mo合金
,
拉伸性能
,
位错结构
,
断裂特性
周杨
,
李小武
,
张广平
,
张哲峰
材料科学与工艺
为了更细致地揭示面心立方金属单晶体的循环变形机制,利用扫描电镜电子通道衬度(SEM-ECC)技术观察研究了Schmid因子为0.5的[4 18 41]单滑移取向铜单晶体的循环饱和位错结构.实验表明,在单滑移铜单晶体中,胞结构除了在高应变幅下的循环变形中出现外,还可能出现在循环应力-应变(CSS)曲线平台区的较低塑性应变幅下.驻留滑移带(PSBs)会随应变幅的增大而在试样表面聚集成内部含有位错胞的粗滑移带,带内的位错胞结构被认为是由于带内滑移阻力增大引起的应变集中所致形成的.此外,CSS曲线高应变幅区起始部分对应的循环饱和位错结构观察揭示出迷宫结构和胞结构是由PSBs逐渐演变而成的.
关键词:
铜单晶
,
循环变形
,
位错结构
,
SEM-ECC
,
驻留滑移带PSBs
王珊
,
汪明朴
,
陈畅
,
夏福中
,
左波
,
张婉
材料热处理学报
通过显微硬度分析、X射线衍射分析和TEM详细研究了钽及钽钨合金在冷轧变形过程中的组织和性能演变规律,结果表明：W在Ta中具有晶粒细化和强化作用,Ta、Ta-2.5%W和Ta-7.5%W合金在1400℃温度退火1 h后的再结晶晶粒的平均尺寸为45、20和15μm;在冷轧过程中,随着变形量的增加,钽和钽钨合金的显微硬度都逐步提高,当变形量达到99%时,Ta、Ta-2.5%W和Ta-7.5%W的显微硬度分别达到了243、309和359 HV;在Ta中添加W后,合金的位错密度会得到极大的提高,其中Ta-7.5%W合金的位错密度比Ta的高一个数量级;钽和钽钨合金各取向的晶粒中的位错密度不同,其中{200}、{211}、{222}和{110}取向的位错密度依次增大,这与Taylor因子计算的结果一致;TEM研究表明,{100}取向的晶粒中形成了位错胞结构,而{110}取向的晶粒中形成了形变带组织。
关键词:
Ta-W合金
,
冷轧
,
织构
,
位错结构
李小武
,
曹昕明
,
马超群
金属学报
doi:10.3321/j.issn:0412-1961.2009.07.004
在恒塑性应变幅εp1控制条件下研究了含富Cr沉淀颗粒的单滑移取向Fe-35%Cr合金(质量分数)单晶体的疲劳变形特征.实验结果和分析表明,当εp1≥2.5x 10-3时,由于运动的位错易于切过细小富Cr沉淀颗粒,导致在循环刚开始第1周的拉伸阶段出现了明显的应力软化现象,并接着在疲劳早期阶段表现出轻微循环软化现象.而且,晶体在循环过程中表现出一定程度的拉一压应力不对称性,这种增强的应力不对称性与细小富Cr沉淀颗粒的变形不稳定性有关.由大量细小滑移线聚集而成的粗滑移带以及高应变幅下形成的扭折带是该晶体主要的滑移变形特征.主裂纹大致沿主滑移面发展并最终沿此开裂,同时伴随有一些形态各异的二次裂纹在表面萌生.微观结构观察发现,在低应变幅(εp1=5.0x 10-4)下就有类驻留滑移带(PSB)楼梯结构形成,其体积分数随εp1的增大而增加.当εp1增大到5.0×10-3时,位错胞结构成为其主要微观结构特征.
关键词:
Fe-Cr合金
,
单晶体
,
疲劳
,
沉淀颗粒
,
滑移变形
,
位错结构
颜莹
,
卢蒙
,
李小武
金属学报
doi:10.3724/SP.J.1037.2012.00684
在恒应力幅下对粗晶纯Al进行不同疲劳寿命分数D(D=2％-75％)的预疲劳变形,研究预疲劳变形对其单向拉伸行为、断口表面变形特征和位错组态的影响.结果表明,随着D的提高,粗晶纯Al的表面挤出和侵入现象加重,晶内的不均匀变形程度增大,导致沿滑移带和晶界萌生微裂纹和微孔洞以及随后的连接,当D高达75％时,三叉晶界节点处产生较长的沿晶裂纹.疲劳位错组态由退火时松散的胞状结构演变成规整的胞状结构和亚晶,但亚晶尺寸并未发生明显变化.预疲劳的粗晶纯Al单向拉伸后,其屈服强度明显提高,但随D的提高,屈服强度变化不大,抗拉强度呈现先降低再升高和最终急剧下降的趋势,但其加工硬化能力较弱.单向拉伸断口由纤维区和剪切唇区组成.纤维区韧窝的数量随D的提高而增多,尺寸减小,当D=50％时,韧窝数量下降,尺寸增大,断口呈现撕裂特征.单向拉伸后的亚结构主要为亚晶和亚晶内的位错胞状结构,随着D的提高,亚晶先减小后增大,亚晶的细化和亚晶内位错胞状结构的形成使预疲劳后的粗晶纯Al具有较高的最大均匀延伸率.
关键词:
粗晶纯Al
,
预疲劳变形
,
单向拉伸
,
断口
,
位错结构
XIA Yuebo WANG Zhongguang DU Xiukui Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
China XIA Yuebo
,
Associate Professor
,
Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
China
金属学报(英文版)
Cyclic deformation in symmetrical push-pull mode was carried out at room temperature in air using a Schenck hydropuls machine.The total strain amplitude which was kept constant dur- ing the test ranged from ±0.004 to±0.012.The 0.2% offset yield stress σ_(0.2f) in tension and σ_(0.2r) in compression and peak stress σ were measured from the stress-strain hysteresis loop at various cycles.The Bauschinger strenghth differential factor(BSDF)was then calcu- lated from σ_(0.2f) and σ_(0.2r).The energy loss △E of each cycle was determined from hysteresis loop areas.These parameters,BSDF,σ and △E,appear to have two distinctively different stages. The dislocation structures were observed using TEM in specimens deformed cyclically,for various cycles.The observation shows that the dislocations pile-up mainly against grain boundaries and there exist large amount of deformation twins.The addition of 0.25 wt-% ni- trogen reduced the stacking fault energy of the alloy significantly.Cross-slip and climb are therefore rather difficult to occur during the cyclic deformation at room temperature,and well-defined dislocation cells and walls can only be seen at the final stage of fatigue.
关键词:
Bausckinger effect
,
null
,
null
GONG Hai
,
ZHANG Xiumu Department of Materials
,
Dalian Railway Institute
,
Dalian
,
116022 China.Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
110015
,
China.
材料科学技术（英文）
The morphology and substructure of mixed martensites in ferrous alloys have been examined by using optical and transmission electron microscope. The results indicated that the main formation se- quence of martensitic morphology was butterfly→ plate→lath,with decreasing forming temperatures when the plastic accommodation takes place in the parent phase,which is affected by the transforma- tion strain fiélds.It was shown that the martensite morphology is not only decided by the forming temperature alone,but also by the dislocation struc- ture in austenite before the transformation.
关键词:
martensite morphology
,
null
,
null
SUN Zhengming
,
WANG Zhongguang
,
AI Suhua Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
China. To whom correspondence should be addressed.
材料科学技术（英文）
Low cycle fatigue tests under plastic strain control were carried out with a dual-phase steel containing 23 Vol.-% martensite. Specimens hardened rapidly at first few cycles followed by a slight softening to saturation stages when cycled at higher strain amplitudes, whereas at lower strain amplitudes the specimens presented continually hardening for a long time until saturation. TEM examination of the saturation dislocation structures show that clusters, parallel walls and cells were found at low, medium and high strain amplitude, respectively. It also has been found that the martensite/ferrite interfaces did not affect the dislocation structures signi- ficantly when a specimen was fatigued at lower strain amplitude. However, the dislocation struc- ture adjacent to the two-phase boundary is dif- ferent to some extent from that in the remote regions in the ferrite when a higher strain amplitude is applied.
关键词:
cyclic deformation
,
null
,
null
