共查询到20条相似文献,搜索用时 125 毫秒
1.
通过分析一种Ti-Mo-Nb-Al钛合金棒材的室温拉伸性能,确定了该合金的最佳固溶和时效热处理制度结果表明,以800℃固溶处理加560-600℃时效处理的棒材,可以得到较好的综合拉伸性能。 相似文献
2.
通过热压放热反应合成工艺制备的NiAl-200vol%TiC原位复合材料,它的平均室温断裂韧性比单相NiAl提高了50%,断口形貌及裂纹扩展路径观查表明,裂纹偏转机制是复合材料的主要韧化机制。 相似文献
3.
研究了Ti-34Al,Ti-34Al-0.5Sb-0.03Mo,Ti-34Al-1.0Sb-0.07Mo合金在900℃的氧化行为和机理,发现在TiAl基合金中复合添加Sb和Mo以后,氧化增重量增加,主要是由于Mo氧化生成易挥发的MoO3引起的,三种合金的氧化过程都遵循氧化剥循环,残余氧化膜的平均度随合金元素添加而下降,在基体中不产生大的元素富集,添加合金元素可以促进氧化膜的种类由第一阶段向第二阶段 相似文献
4.
5.
本文利用电子拉伸试验,扫描电镜,金相显微镜研究了Cu-Zn-Mn-Al-Ti合金的细化效果,断裂方式,记忆性能及伪弹性。结果表明:试验合金的铸态,轧态和淬火态组织得到明显细化。晶粒细化后合金室温拉伸断裂强度为750MPa,断列应变为6.6%,同未细化的Cu基记忆合金相比强度大大提高,塑性也有所改善。低温拉伸时呈穿晶断裂,断口主要为准解理台阶;高温拉伸时呈微孔聚集型断裂。试验合金的室温完全可恢复应变 相似文献
6.
7.
用SEM动态拉伸装置观察了δ-Al2O3短纤维增强Al-5.5Mg合金复合材料微观断裂过程,分析了断裂机制,根据动态拉伸结果计算了界面剪切强度。 相似文献
8.
9.
本文研究了利用快速凝固粉末冶金工艺制备高阻尼Al-Zn-Mg-Cu系合金。通过拉伸性能与阻尼性能的测试,以及显微组织分析,探讨了纯铝及石墨对合金拉伸性能及阻尼性能的影响。结果表明:Al-Zn-Mg-Cu/15wt%Al合金的室温拉伸性能已达到LC9CGS1的水平,阻尼性能为Q=6.0×10^-3;在室温至300℃温度范围内,随着温度的升高,合金的阻尼能力提高;合金的阻尼机制属复合型机制。 相似文献
10.
11.
M. MOSTAFAVI D. J. SMITH M. J. PAVIER 《Fatigue & Fracture of Engineering Materials & Structures》2010,33(11):724-739
It is generally believed that a lower bound on the fracture toughness of a material is obtained from a standard test, particularly in metals where yielding occurs prior to fracture. The understanding is that in such a test the material around the crack tip is highly constrained hence reducing the extent of yielding. In this paper, we report the results of fracture tests where a tensile load is applied to a biaxial aluminium alloy specimen in the direction parallel to the crack front in addition to the fracturing load normal to the crack surface. We show that in this case a lower fracture toughness is measured than that obtained from a standard test. Indeed, for the highest value of tensile load used in our tests the J‐integral at fracture was half the value measured in a standard test. It is also shown that the volume of the plastic region can be used to measure the effect of constraint, irrespective of the manner in which the constraint arises. This approach suggests an even lower fracture toughness may be obtained than that measured here in certain loading conditions. 相似文献
12.
In this study, the tensile properties, high cycle fatigue behavior and plane-strain fracture toughness of the sand-cast Mg–10Gd–3Y–0.5Zr magnesium alloy were investigated, comparison to that of sand-cast plus T6 heat treated magnesium alloy which named after sand-cast-T6. The results showed that the tensile properties of the sand-cast alloy are greatly improved after T6 heat treatment, and the fatigue strength (at 107 cycles) of the sand-cast Mg–10Gd–3Y–0.5Zr magnesium alloy increases from 95 to 120 MPa after T6 heat treatment, i.e. the improvement of 26% in fatigue strength has been achieved. The plane-strain fracture toughnesses KIC of the sand-cast and sand-cast-T6 alloys are about 12.1 and 16.3 MPa m1/2, respectively. In addition, crack initiation, crack propagation and fracture behavior of the studied alloys after tensile test, high cycle fatigue test and plane-strain fracture toughness test were also investigated systematically. 相似文献
13.
为研究FRP增强混凝土梁失稳前断裂过程,该文基于混凝土断裂力学理论和非线性FRP-混凝土界面粘结滑移规律,建立了一个跨中裂缝导致界面脱粘的粘聚区模型,采用解析方法推导了FRP增强混凝土梁界面剪切应力、FRP拉应力以及失稳前断裂韧度的公式,为分析FRP-混凝土界面脱粘提供了一种有效的方法,并开展了动态荷载下4种不同初始缝高比(0.2、0.3、0.4和0.5)的FRP增强混凝土梁三点弯曲试验。结果表明,FRP增强混凝土梁的起裂荷载和阻裂荷载随着初始缝高比的增大而逐渐减小,但初始缝高比为0.4时,试件起裂最晚;起裂韧度和阻裂韧度不随初始缝高比的变化而变化,表现出与其他文献类似的规律,验证了断裂韧度解析解的正确性。 相似文献
14.
Experiments investigating dynamic tensile fracture were performed on the extruded rods of 2024‐T4 and 7075‐T6 aluminum alloys under varying loading conditions. The initial yield stress and fracture strain of 7075‐T6 alloy obtained in spilt Hopkinson tension bar tests are higher than that of 2024‐T4 alloy. But the initiation fracture toughness and spall strength of 2024‐T4 alloy are higher than those of 7075‐T6 alloy in three‐point bending and plate impact experiments, which indicates that 2024‐T4 alloy has better crack initiation tolerance and stronger spall failure resistance. Based on metallurgical investigations by using optical and scanning electron microscopes, it is revealed that the microstructure has a profound effect on the dynamic tensile fracture mechanism of each aluminum alloy. The 2024‐T4 alloy is relatively brittle due to voids or cracks nucleated at many coherent CuMgAl2 precipitate phases in the grain interiors, and the fracture mode is predominantly transgranular. The 7075‐T6 alloy exhibits relatively ductile fracture because voids or cracks growth is partly intergranular along the grain boundaries and partly transgranular by void formation around coarse intermetallic particles. The obvious differences of damage distribution and void coalescence mechanisms for 2024‐T4 and 7075‐T6 alloys under plate impact are also discussed. 相似文献
15.
目的 研究影响铸造、锻造和粉末冶金TC4钛合金的损伤容限行为差异的主要因素。方法 分别从裂纹尖端塑性变形行为、二次裂纹及断口表面粗糙度3个方面对比,分析造成3种成形方法制备的TC4钛合金的断裂韧性和疲劳裂纹扩展速率差异的原因。结果 铸造TC4钛合金断裂韧性优于锻造和粉末冶金TC4钛合金,主要是因为新产生的裂纹面积大,消耗更多断裂能量。铸造TC4钛合金疲劳裂纹扩展速率低于锻造、粉末冶金TC4钛合金,其主要原因为曲折的裂纹路径和断面粗糙度诱发裂纹闭合效应以及长而深的二次裂纹。结论 3种成形方法制备TC4钛合金损伤容限行为差异的主要原因是断裂形成了不同裂纹路径形貌。 相似文献
16.
17.
S. SAXENA N. RAMAKRISHNAN J. S. CHOUHAN 《Fatigue & Fracture of Engineering Materials & Structures》2011,34(3):205-214
There is an increasing effort to use critical stretch zone width (SZW) for the evaluation of initiation fracture toughness that is considered as geometry independent material property. The existing numerical SZW evaluation method is based on crack tip opening displacement measurement, which is evaluated using various definitions. This numerical method also does not define the critical stage for critical SZW measurement. This work attempts to establish a procedure for numerical determination of SZW, its critical value (SZWc) and initiation fracture toughness using tensile test data. The proposed methodology also tries to explain the mechanism involved in the creation of stretched zone and thus defines the stage to calculate critical SZW. Numerical analyses have also been carried out to understand the role of crack tip constraint in standard fracture specimen during the blunting process and the tensile test sample. 相似文献
18.
A commercial magnesium alloy, AZ31 in hot-rolled condition, has been processed by equal channel angular pressing (ECAP) to get microstructure modified. Uniaxial tensile tests were conducted along the rolling/extrusion direction for as-received AZ31 alloy and ECAPed AZ31 alloy. Then, three point bending fracture tests were conducted for specimens with a pre-crack perpendicular to the extruded direction. Digital image correlation (DIC) technique was adopted to determine the deformation field around the crack tip. The fracture surfaces of the failed specimens after tensile tests and fracture tests were observed by Scanning Electron Microscope (SEM). To explore the deformation mechanism, the microstructure and texture of different regions on the deformed specimens were examined through electron backscatter diffraction (EBSD). The results show ECAP process improves both the tensile elongation and fracture toughness of AZ31 alloy. Different from the slip dominated deformation mechanism in the tensile test, deformation twinning presents in the deformation zone adjacent to the crack tip in the three point bending fracture tests. The fracture surface is characterized by co-occurrence of dimple and cleavage features. 相似文献
19.
20.
对BT20钛合金及其激光焊接接头的断裂韧性进行了研究.同时分析了合金及激光焊接接头的硬度分布及显微组织.断裂实验表明,除了一个焊接接头紧凑拉伸(CT)试样是脆性启裂外,其它CT试样均在裂纹延性启裂并缓慢扩展后,发生脆性失稳断裂.母材的断裂韧性明显高于焊接接头,轧制方向对母材断裂韧性的影响不明显.焊接热影响区的断裂韧性介于母材和焊缝金属之间.本研究采用的焊后热处理没有改善焊接接头的断裂韧性,还有进一步恶化的趋势.添加活性剂对焊缝金属的断裂韧性没有明显作用,但对延性裂纹扩展长度有所改善. 相似文献