Effects of thermomechanical treatment on the mechanical properties and microstructures of 6013 alloy

The mechanical properties and microstructures of 6013 alloy after different thermomechanical treatments were investigated. The detailed dislocation configurations after deformation and morphologies of age hardening precipitates were examined through transmission electron microscopy (TEM). The experimental results show that the thermomechanical treatment can significantly enhance the strength of 6013 alloy, and has a similar influence trend on single and two-step aging behaviors. With the increasing deformation ratio, the peak-hardness (HV_max) increases, the time to HV_max shortens, and the density of tangled dislocation network increases. The aging precipitates become larger and inhomogeneous by applying thernomechanical treatment. Funded by the National Key Technology R&D Program of China (No.2007BAE38B01)     

Effect of heat treatment on microstructures and mechanical properties of Al-6Zn-2Mg-1.5Cu-0.4Er alloy

The microstructures and mechanical properties of A1-6Zn-2Mg-1.5Cu-0.4Er alloy under different treatment conditions were investigated by transmission electron microscopy (TEM) observation, and tensile properties and hardness test, respectively. The relationship between mechanical properties and microstructures of the alloys was discussed. With trace Er addition to A1-Zn-Mg-Cu alloy, Er and Al interact to form Al3Er phase, which is coherent with α(Al) matrix. The results show that A1-Zn-Mg-Cu alloy after retr...     

机械合金化法制备W-Cu合金粉末的研究

将W80Cu20（n（W）：n（Cu）=4：1）混合粉末在QM-BP式行星式高能球磨机中球磨进行机械合金化,研究了不同球磨时间对W-Cu混合粉末组织的影响.采用XRD和SEM对不同球磨时间的粉末进行分析,结果显示随着球磨时间的增加,混合粉末产生合金化效果不断增强,Cu固溶于W中,并且晶粒尺寸得到一定的细化.     

Effect of heat-treatment on the microstructures and mechanical properties of Mg-10Zn-5Al-0.1Sb-xCu magnesium alloy

The effects of the solution and aging treatment on microstructures and mechanical properties of the Mg-10Zn-5Al-0.1Sb-XCu cast magnesium alloys were investigated by brinell hardness measurement, scanning electron microscopy (SEM), energy spectrum analyzing apparatus and X-ray diffraction (XRD). The experimental results show that the strip-like τ-Mg₃₂ (Al, Zn)₄₉ phase is shown at the grain boundaries and Mg₂Cu phase become smaller, even granular after solution treatment at 350 °C for 24 h. By ageing treatment at 180 °C, the ternary strengthening phase (τ phase) precipitates gradually at or around grain boundary. With increasing aging time, the micro-hardness improves obviously and up to the maximum (105.9 HV) at aging time of 36 h. In addition, the tensile-strengths at room temperature and at an elevated temperature respectively reach 228 MPa and 176 MPa, which is increased by 20% and 10%, respectively.     

Si和Ca对铸态Mg-5Sn-0.5Sr合金组织和性能的影响

为了提高镁合金的耐热性能,在Mg-5Sn-0.5Sr合金中加入Si和Ca等合金化元素,设计了Mg-5Sn-0.5Sr-xSi(x=1,2)和Mg-5Sn-0.5Sr-xSi-0.5Ca(x=1,2)合金.采用x-射线衍射仪(XRD)、光学显微镜(OM)与扫描电镜(SEM)研究了合金的相组成及显微组织,并利用力学性能试验机测定了合金的拉伸性能.结果表明,Mg-5Sn-0.5Sr-xSi(x=1,2)合金组织由沿α-Mg晶界析出的共晶Mg₂Sn、Mg₂Si相与α-Mg晶内初生MgSnSr相组成,且Mg₂Si相的质量分数随Si元素的增加而增加.对于Mg-5Sn-0.5Sr-xSi-0.5Ca(x=1,2)合金而言,加入Ca元素能够显著促进初生(Ca,Sr)MgSn相的形成,而抑制晶界上Mg₂Sn相的析出.     

轧制工艺对ZA35合金组织和性能的影响

为了提高ZA35合金的力学性能,采用轧制工艺制备ZA35合金板坯,利用x-射线衍射仪(XRD)、金相显微镜(OE)、扫描电子显微镜(SEM)以及能谱分析(EDS)等技术分析和检测了ZA35合金铸态、不同轧制态和热处理态的显微组织和性能.结果表明:轧制可以显著提高ZA35合金的综合力学性能,使抗拉强度提高了27.8%,硬度指标提高了36.4%,伸长率比铸态增加了近2倍.轧制使合金组织细化,初生α相增多,ε相由块状变成细小的点状弥散分布于枝晶间.轧制合金在经过365℃固溶3h和120℃时效12h热处理后合金力学性能最好,抗拉强度达到512MPa、伸长率为4.9%、硬度为HB127.     

热处理对2524铝合金显微组织及力学性能影响

在400℃下对铸态2524铝合金进行轧制成形,总变形量为90%,采用光学金相显微镜、拉伸试验机等设备检测轧制板材显微组织及力学性能.研究结果表明：随着固溶温度的升高,Al2Cu,Al2CuMg等第二相粒子数量逐渐减少,在490℃～500℃下基本固溶进铝基体中,其显微硬度值随着固溶温度的升高逐渐增大,当固溶温度为490℃时其显微硬度值为131.4 HV;2524铝合金轧制板材经490℃/20 min＋190℃/22 h处理后,其抗拉强度为485 MPa,延伸率为13.5%.     

Effects of HIPing pressure on microstructures and properties of TiAl alloy

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Effect of low temperature thermo-mechanical treatment on microstructures and mechanical properties of TC4 alloy

The effects of low temperature thermo-mechanical treatment (LTTMT) on microstructures and mechanical properties of Ti-6Al-4V (TC4) alloy were studied by optical microscopy (OM), tensile test, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results confirm that the strength of TC4 alloy can be improved obviously by LTTMT processing, which combines strain strengthening with aging strengthening. The effect of LTTMT on the alloy depends on the microstructure of the refined and dispersed α+β phase on the basis of high dislocation density by pre-deformation below recrystallization temperature. The tensile strength decreases with the increase of pre-deformation reduction. The optimal processing parameters of LTTMT for TC4 alloy are as follows:solution treatment at 900 ℃ for 15 min, pre-deformation in the range of 600-700 ℃ with a reduction of 35%, finally aging at 540 ℃ for 4 h followed by air-cooling.     

Effect of heat treatment on microstructures and mechanical properties of a bulk nanostructured Al-Zn-Mg-Cu alloy

A bulk nanostructured Al-10.0Zn-2.8Mg-1.8Cu alloy was synthesized by cryomilling first and then by spark plasma sintering (SPS), and the effect of heat treatment on the microstructures and mechanical properties of this alloy were studied. Most MgZn_2 particles with a coarse size lie on the grain boundaries of the SPS-processed sample. After solid solution and artificial aging,fine spherical-like MgZn_2 particles precipitate uniformly in the grain interiors. No obvious grain growth is found after the heat treatment. A nanoindentation study indicates that no clear change is found in the Yong's modulus of the nanostructured alloy after the heat treatment.However, the hardness of the nanostructured alloy increases by about 33% after the heat treatment, which is attributed to the effect of precipitation-hardening.     

Evolution of surface microstructure of Cu-50Cr alloy treated by high current pulsed electron beam

A Cu-50Cr alloy was treated by the high current pulsed electron beam(HCPEB)at 20 and 30 ke V with pulse numbers ranging from 1 to 100.Surface morphologies and microstructures of specimens before and after the treatments were investigated by employing scanning electron microscopy and X-ray diffraction.Results show that the HCPEB technique is able to induce remarkable surface modifications for the Cu-50Cr alloy.Cracks in Cr phases appear even after one-pulse treatment and their density always increases with the pulse number.Formation reason for these cracks is attributed to quasi-static thermal stresses accumulated along the specimen surface.Craters with typical morphologies are formed due to the dynamic thermal field induced by the HCPEB and they are found to prefer the sites near cracks or boundaries between neighboring Cr phases.Another microstructural characteristic produced by the HCPEB is the fine Cr spheroids,which are determined to be due to occurrence of liquid phase separation in the Cu-50Cr alloy.Finally,a general microstructural evolution profile that incorporates various HCPEB-induced surface features is tentatively outlined.     

Formation mechanism of Ti5Si3 powder by mechanical alloying

The formation mechanism of stoichiometry Ti5Si3 by mechanical alloying (MA) from elemental powders has been investigated. The results of XRD and SEM analyses of the powder show that Ti5Si3 can be synthesized by MA in a planetary mill with two different formation mechanisms. Ti5Si3 was formed gradually with the mechanical collusion reaction (MCR) mechanism under a lower impact energy, and the Ti5Si3 was formed abruptly with the self-propagating high-temperature synthesis (SHS) formation mecha-nism under a higher impact energy.     

机械合金化Ni-20Cr-2.5Al合金的电化学腐蚀研究

利用电化学方法,结合XRD、TEM等表面分析技术,研究了机械合金化Ni-20Cr-2．5Al及粗晶Ni- 20Cr-2．5Al合金在3．5％NaCl溶液中的腐蚀性能．结果表明粗晶Ni-20Cr-2．5Al合金在3．5％NaCl溶液中的电化学性能要好于机械合金化方法制备的Ni-20Cr-2．5Al合金．     

固溶处理对挤压WE43镁合金的影响

为了改善WE43镁合金的室温塑性,提高其利用价值,研究了不同固溶处理方法对WE43镁合金挤压件力学性能和微观组织的影响.结果表明：固溶处理对WE43镁合金挤压件的抗拉强度影响不大,但能够大幅度提高其室温的伸长率和断面收缩率,从而使WE43镁合金具有优良的综合力学性能.当固溶温度为525℃、固溶时间为8h时,全部的MgYNd稀土相和大部分的Mg12Nd溶解到Mg基体中,剩余少量的Mg12Nd转变为细小的颗粒状,均匀分布在晶界处,此时挤压件的抗拉强度为223MPa,室温伸长率达到峰值29.2%.     

脉冲电流对Ti-6Al-4V合金显微组织及力学性能的影响

采用组织观察、性能检测、断口分析等方法研究了脉冲电流对Ti-6Al-4V合金显微组织及力学性能的影响。结果表明,脉冲电流使试样瞬间急速升温、产生较高的热压应力,并发生α→β相变,随后试样快速降温冷却发生β→α′相变。由于急速升温和快速冷却,新相的形核率增加且无充足时间长大,使合金的显微组织细化,而相变和组织细化导致了合金力学性能提高和电阻率变化。适当优化电脉冲处理工艺参数可使Ti-6Al-4V合金的综合力学性能明显提高。通过测量电阻变化可间接表征电脉冲处理后材料微观组织结构的变化程度。     

Effect of continuous annealing parameters on the mechanical properties and microstructures of a cold rolled dual phase steel

A cold rolled dual phase (DP) steel with the C-Si-Mn alloy system was trial-produced in the laboratory,utilizing a Glee-ble-3800 thermal simulator. The effects of continuous annealing parameters on the mechanical properties and microstructures of the DP steel were investigated by mechanical testing and microstructure observation. The results show that soaking between 760 and 820°C for more than 80 s,rapid cooling at the rate of more than 30°C/s from the quenching temperature between 620 and 680°C,and overag...     

Influence of Mg2N2 powder on microstructures and mechanical properties of AZ31 Mg alloy

In order to obtain an effective and reliable grain refiner for Mg-Al alloys, 1% (mass fraction) Mg3N2 was added into AZ31 Mg alloy. The microstructures of the Mg alloys were studied by optical microscopy, scan electron microscopy and X-ray energy dispersive spectroscopy, and the mechanical properties were determined. The results show that adding a small amount of Mg3N2 to AZ31 Mg alloy can refine the grain size from 103 to 58 μm. The ultimate tensile strength and elongation of AZ31 Mg alloy are 174.1MPa and 8.3%, respectively. After the addition of 1% Mg3N2, the ultimate tensile strength and elongation of AZ31 Mg alloy are increased up to 198.7 MPa and 11.8%, respectively. The grain refinement mechanism is that AIN is formed after Mg3N2 is added.Both A1N and Mg phases are of HCP lattice structure, and the disregistry between Mg phases and AIN along (0001)Mg//(0001)AlN is 3.04%, which is very effective for heterogeneous nucleation.