Effects of heat treatment on the microstructure and mechanical properties of ZA84 magnesium alloy

The effects of heat treatment on the microstructure and mechanical properties of ZA84 (Mg-8Zn-4Al-0.25Mn) alloy were investigated. The results indicate that the as-cast microstructure of the alloy is mainly composed of α-Mg matrix and two different morphologies of precipitates (continuous and quasi-continuous Mg32(Al,Zn)49 phases and isolated Mg5Al2Zn2 phases). After solid solution treatment at 345°C, the Mg32(Al,Zn)49 phases change from continuous and quasi-continuous net to disconnected acute angle shape,...     

Effects of heat treatment on microstructure and mechanical properties of Fe-Co-Ni-Cr-Mo-C alloy

A kind of Fe-Co-Ni-Cr-Mo-C alloy was designed for valve seat use. The effects of the quenching temperature, tempering time and tempering temperature on the mechanical properties and microstructure of the alloy were investigated. The results show that the hardness decreases, while tensile strength (σb), transverse rupture strength (σbb) and impact toughness(Kit) increase after the alloy is quenched and tempered. The best complex property (σb, 446 MPa; σbb ,793 MPa; Kic, 2.96 J/cm2 ) can be obtained when the alloy is quenched at 1 100 ℃ and tempered at 650 ℃. The results of X-ray diffraction and energy dispersive X-ray analysis (EDX) show that the major strengthening phases are carbides such as (Fe, Cr)7 C3 and Fe2 MoC. The obvious secondary hardening appears when the alloy is tempered at 550 ℃, which results from the precipitated carbides of Cr and Mo in the alloy from the matrix and the heat-resistant retained austenite .     

热处理对反向挤压AZ80镁合金组织与性能的影响

采用光学和扫描电子显微观察、X射线衍射及拉伸试验研究了反向挤压AZ80镁合金不同热处理状态下的显微组织及性能．结果表明：反向挤压AZ80镁合金热处理后析出的β－Mg17Al12相（β相）在不同热处理状态下形貌不同．经T6热处理后,口相在晶界处呈层片状析出,与挤压态相比,合金的强度稍有降低,但延伸率明显提高;经T5热处理后,卢相在晶界处仍呈层片状,而在晶内呈颗粒状,与挤压态相比,合金的强度明显提高,但延伸率降低．     

热处理对挤压变形AZ61镁合金力学性能的影响

研究了几种热处理对挤压变形AZ61镁合金力学性能的影响，得出：经过固溶处理及固溶+时效处理可以使强度有所降低，但塑性提高较大，而单纯的时效处理则不能使强度降低；在挤压变形状态下，试验温度对冲击韧性的影响不大，固溶处理可以提高室温下的冲击韧性，但在低温下两者基本相同.而其它几种处理则使冲击韧性降低，并且这种冲击韧性的降低程度随着试验温度的降低而减小.     

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...     

Microstructure, cold rolling, heat treatment, and mechanical properties of Mg-Li alloys

The magnesium-lithium (Mg-Li) alloy exhibits two phase structures between 5.7wt% and 10.3wt% Li contents, consisting of the α (hcp) Mg-rich and the β (bcc) Li-rich phases, at room temperature. In the experiment, Mg-5Li-2Zn, Mg-9Li-2Zn, Mg-16Li-2Zn, Mg-22Li-2Zn, Mg-5Li-2Zn-2Ca, Mg-9Li-2Zn-2Ca, Mg-16Li-2Zn-2Ca, and Mg-22Li-2Zn-2Ca (wt%) were melted. During the melting process, the flux, which was composed of lithium chloride (LiCl) and lithium fluoride (LiF) in the proportion of 3:1 (mass ratio) and argon gas were used to protect the alloys from oxidation. The microstructure, mechanical properties, and cold-rolling workability of the wrought alloys were studied. The crystal grain of the alloys (adding Ga) is fine. The hardness of the studied alloys decreases with an increase in element Li. The density of the studied alloys is in the range of 1.187 to 1.617 g/cm3. The reduction of the Mg-16Li-2Zn and Mg-22Li-2Zn alloys can exceed 85% at room temperature. The Mg-9Li-2Zn-2Ca alloy was heat treated at 300°C for 8, 12, 16, and 24 h, respectively. The optimum heat treatment of the Mg-9Li-2Zn-2Ca alloy is 300°C×12h by metallographic observation and by studying the mechanical properties of the alloys.     

Effect of cyclic heat treatment on microstructure and mechanical properties of 50CrV4 steel

An annealed 50 Cr V4 steel was subjected to cyclic heat treatment process that consists of repeated short-duration(200 s)held at 840 °C(above Ac3 temperature of 790 °C) and short-duration(100 s) held at 700 °C(below Ac1 temperature of 710 °C). The spheroidization ratio of cementite and the average size of particles increase with increasing the cyclic number of heat treatment. After5-cycle heat treatment, the spheroidization ratio of cementite is 100%, and the average size of the cementite particles is about0.53 μm. After cyclic heat treatment, the hardness, ultimate tensile strength and yield strength of the experimental steel gradually decrease with increasing cyclic number of heat treatment. The elongation of the as-received specimens is about 7.4%, the elongation of the 1-cycle specimen is 14.3%, and the elongation of 5-cycle specimen reaches a peak value of 22.5%, thereafter marginally decreases to 18.3% after 6-cycle heat treatment. Accordingly, the fractured surface initially exhibits the regions of wavy lamellar fracture. By increasing the cyclic number of heat treatment cycles, the regions of dimples consume the entire fractured surface gradually. Some large dimples can be found in the fracture surface of the specimen subjected to six heat treatment cycles.     

Effects of cryogenic treatment on mechanical properties and microstructure of Fe-Cr-Mo-Ni-C-Co alloy

Fe-Cr-Mo-Ni-C-Co alloy was quenched in liquid nitrogen and held for 24 h. Hardness tester, OM, XRD, SEM were used to investigate the mechanical properties and microstructures of the alloy. The results show that the hardness increases by 1-2 （HRC） and the compressive strength decreases slightly after cryogenic treatment. The increase in hardness is attributed to the transformation from austenite to martensite and the precipitation of the very tiny carbide η-Fe2C. The decrease in compressive strength is caused by residual stress. The great amount of carbides, such as Cr7C3 and Fe2MoC, in the alloy and the obvious difference in thermal expansion coefficient between these carbides and the matrix at the cryogenic temperatures lead to this residual stress. The microscopy of cryogenic martensite is different from that of the non-cryogenic martensite. The cryogenic martensite is long and fine; while the non-cryogenic martensite is short and coarse. There is obvious surface relief of the cryogenic martensite transformation. It is not orientational of this kind surface relief and the boundary of this surface relief is smooth and in a shape of butterfly. The surface relief in the non-cryogenic martensite is wide and arranged in parallel, and the boundary of surface relief is not smooth. These characteristics may imply different growth ways of the two kinds of martensite.     

热处理对无凝固收缩铝硅合金组织和性能的影响

为了寻找一种无凝固收缩铝硅合金的最佳热处理工艺,主要研究了热处理对无凝固收缩铝硅合金组织和力学性能的影响规律.结果发现：无凝固收缩铝硅合金的组织主要受固溶温度的影响,随固溶温度的提高,合金中化合物相减少、共晶硅和初生硅球化;无凝固收缩铝硅合金的硬度随固溶温度和时效温度的升高及时效时间的延长均具有先增大后减小的规律,固溶温度为803～813 K、时效温度为463 K、时效时间为10 h时合金的硬度提高最大;T6处理后无凝固收缩铝硅合金的抗拉强度达到了279～302 MPa,比国际上的类似成分合金KS270、KS271和KS272合金高了40%左右.     

热处理对TC4钛合金厚板组织和性能的影响

选区激光熔化(selective laser melting, SLM)成形TC4合金组织因极快的冷却速度形成了大量硬脆的针状α'马氏体, 导致SLM成形TC4合金塑性显著降低, 严重限制了SLM成形TC4合金的工程应用。为了提高SLM成形TC4合金的塑性, 研究了4种不同热处理温度对SLM成形TC4合金微观组织及力学性能的影响。结果表明, 4种不同温度热处理后, 初生β晶粒内的针状α'相转变为α相, 且随着温度从860 ℃增加到950 ℃, 针状α相形态从网篮状转变为相同取向的集束, α晶粒尺寸从1.73 μm增大到2.32 μm, β相体积分数从0.4%增大到2.7%。抗拉强度从961 MPa降低到870 MPa, 而延伸率则先升高后降低, 其中890 ℃热处理的抗拉强度为941 MPa, 延伸率为11.1%, 相对于未热处理试样, 延伸率提高了126.5%。

     

Effects of heat treatment on the microstructures and mechanical properties of a new type of nitrogen-containing die steel

Nitrogen can increase the strength of steels without weakening the toughness and improve the corrosion resistance at the same time. Compared with conventional nitrogen-free die steels, a new type of nitrogen-containing die steel was developed with many superior properties, such as high strength, high hardness, and good toughness. This paper focused on the effects of heat treatment on the microstruc-tures and mechanical properties of the new type of nitrogen-containing die steel, which were investigated by the optimized deformation process and heat treatment. Isothermal spheroidal annealing and high-temperature quenching as well as high-temperature tempering were ap-plied in the experiment by means of an orthogonal method after the steel was multiply forged. The mechanical properties of nitro-gen-containing die steel forgings are better than the standard of NADCA #207-2003.     

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.     

热处理工艺对27SiMn钢组织及力学性能的影响

为得到热处理工艺对27SiMn钢显微组织及力学性能的影响,制定了9种热处理工艺,并对其进行显微组织观察和力学性能测试.实验结果表明,27SiMn钢淬火＋回火后的显微组织与回火温度和时间有关,当回火温度低、时间短时,显微组织为回火屈氏体＋马氏体;当回火温度高、时间长时,显微组织为回火屈氏体＋回火索氏体.同时,回火温度和时间对27SiMn钢的力学性能有很大影响,当回火温度为450℃,时间为45 min时力学性能最高,抗拉强度为1 175 MPa。当热处理温度为490℃,时间为75 min时力学性能最差,抗拉强度为975 MPa.综合分析27SiMn钢热处理最优工艺为900℃淬火＋475℃回火75 min。     

Effects of Ag on microstructure and mechanical properties of 2519 aluminum alloy

The effects of Ag on the microstructure and mechanical properties of 2519 aluminum alloy were investigated by means of tensile test, micro-hardness test, transmission electron microscope and scanning electron microscope. The results show that the addition of 0.3 % （mass fraction） Ag accelerates 2519 aluminum alloy＇s age-hardening, increases its peak hardness and reduces 4 h of peak aged time at 180 ℃. The addition of 0. 3% （mass fraction） Ag increses the tensile strength at room temperature and elevated temperature. This increment at room temperature and 200 ℃ is 24 MPa and 78 MPa, respectively. In contrast, the elongation of 2519 aluminum alloy is decreased with Ag addition. The increase of tensile strength of 2519 aluminum alloy with Ag addition is attributed to the high volume fraction of Ω phase.     

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%.     

热处理对65Mn-Q235爆炸复合钢板性能的影响

研究了热处理对65Mn-Q235爆炸复合钢板的力学性能的影响，结果表明，65Mn-Q235爆炸复合钢板在850℃保温80℃油淬的热处理工艺下，可以获得良好的抗拉强度、弯曲强度、硬度等力学性能．     

退火处理对Ti-Zr-Cu-Be块体非晶合金力学性能的影响

采用铜模铸造法制备了直径为2mm的Ti55-xZr10+xBe27.5Cu7.5(x=0,10,20)块体非晶合金,并对其进行等温退火处理.利用X射线衍射(XRD)、扫描电镜(SEM)、差氏扫描量热仪(DSC)及压缩试验等方法研究了非晶合金的相结构、显微组织和热稳定性,以及退火处理对其力学性能的影响.结果表明:该系列合金在553 K及583 K下保温长达5 h时间内依然表现为非晶态.退火处理后,Ti35Zr30Be27.5Cu7.5合金屈服强度、断裂强度均提到了提高,其中在583 K下保温1 h后屈服强度、断裂强度分别达到了1 921、2 169 MPa;其塑性由处理前的3.47%提高到了6.57%.Ti45Zr20Be27.5Cu7.5合金在退火后其力学性能变化不明显.Ti55Zr10Be27.5Cu7.5合金随着退火温度及保温时间的增加其屈服强度、断裂强度及塑性均明显降低.     

化学成分对锌基合金性能的影响

研究了成分对锌基合金性能的影响,结果表明,ＺＡ－４０合金具有最佳的组织和性能,在锌基合金中起提高耐磨性作用的硬质点为ＣｕＺｎ４。