Y和Ce对Mg-6Al合金挤压铸造组织和性能的影响

借助光学显微镜、扫描电镜和万能拉伸测试仪,对添加稀土Y和Ce的挤压铸造Mg-6Al合金的显微组织和力学性能进行了分析.结果表明,采用挤压铸造工艺,在复合添加稀土Y和Ce后,晶粒组织明显细化,显微组织由网状变为断网状,室温力学性能得到大幅度提高.添加0.5?和0.5%Y时,挤压铸造Mg-6Al合金的抗拉强度从126 MPa提高到了200 MPa,伸长率从1.0%提高到了8.5%.     

Nd对挤压铸造镁合金组织和力学性能的影响

镁合金经Ca合金化处理和稀土Nd变质处理后,在100MPa压力下挤压铸造成形,研究了Nd对Mg-8Al-1.0Ca合金组织和性能的影响。经XRD扫描及EDS能谱分析发现,通过挤压铸造,使得镁合金晶粒细化,有利于位错形成,析出相变得均匀细小,力学性能明显改善;当Nd添加量为0.4%时,镁抗拉强度达到230MPa,屈服强度为121MPa,伸长率为4.8%,合金性能达到最佳,较未变质时分别提高了28%、61%和78%。     

RE对挤压铸造AlSi7Cu4MgMn合金组织和性能的影响

研究了不同RE(Ce、La混合稀土)含量对挤压铸造AlSi7Cu4MgMn合金组织、力学性能及铸造性能的影响。结果表明,RE可提升合金铸造性能,大幅度提高合金成形的良品率。不含RE时,AlSi7Cu4MgMn合金微观组织由α-Al基体、共晶Si相、块状α-Fe相、小块聚集状Al_2Cu相及其他强化相组成;添加适量RE后,块状Fe相转变为短棒状形态,Al_2Cu相细化并形成Al_xCu_4Mg_5Si_4复杂相;过量RE添加会导致合金中富Fe相聚集长大,恶化合金性能。添加0.25%的RE时合金力学性能最佳,抗拉强度为430MPa,屈服强度为392MPa,伸长率为6.8%。     

Mg对反重力铸造ZL116合金组织和性能的影响

通过OM、XRD以及室温拉伸试验等手段,分析了Mg对反重力铸造ZL116合金显微组织和力学性能的影响。结果表明,随着Mg含量提高,ZL116合金的抗拉强度有所提高,伸长率基本没有变化。反重力铸造方式中差压铸造的ZL116合金力学性能最优,低压铸造次之,调压铸造的力学性能差于重力铸造。随着Mg含量提高,ZL116合金中的强化相Mg2Si含量也随之增加,最终导致ZL116合金抗拉强度提高。     

稀土元素La对Zn-Al2合金组织与性能的影响

采用铁模铸造法制备不同稀土元素La含量的Zn-Al2合金;通过光学显微镜、扫描电镜、万能拉伸试验机,研究添加不同含量镧对Zn-Al2合金显微组织、稀土相形态、力学性能的影响。结果表明,随着稀土镧的加入,合金初生相η相尺寸变小,晶粒细化,力学性能提高。当稀土La含量超过0.03%时,初生相η相变大,稀土化合物尺寸增大,偏聚在晶界附近,割裂基体导致力学性能下降。当稀土La含量为0.03%时力学性能最佳,抗拉强度,屈服强度和伸长率依次为262.73 MPa,246.46 MPa和49.5%。     

混合稀土对ZL301合金组织及力学性能的影响

研究了不同混合稀土添加量对铸态及固溶态ZL301合金显微组织和力学性能的影响。结果表明,混合稀土能细化铸态合金的晶粒,形成Al-RE相,沿晶界不连续分布,起到晶界强化作用,从而提高了合金的抗拉强度和伸长率。当混合稀土添加量为0.5%、固溶处理工艺为435℃×16h时,ZL301合金的综合性能达到最佳。当混合稀土添加量为0.8%时,Al-RE相开始沿晶界连续分布,降低了晶界的结合强度,合金的强度和韧性下降。     

变质处理对ZL114A合金组织和性能的影响

利用光学显微镜研究了Al-10%Sr变质剂对ZL114A合金组织的影响。采用T6工艺对金属模铸造的ZL114A合金进行了热处理,并对其拉伸性能进行了测试与分析。结果表明,最佳变质处理工艺为Sr元素的加入量为0.03wt%～0.05wt%,保温时间为30min;Sr元素变质能够明显提高ZL114A-T6合金的抗拉强度和伸长率,当添加0.03%Sr时,抗拉强度和伸长率分别从230 MPa和1%上升到最大值305MPa和8%。     

流变挤压铸造制备LPSO结构增强Mg-Zn-Y-Zr合金及其组织性能

采用流变挤压铸造工艺制备了含有LPSO结构的Mg99.9-3xZnxY2xZr0.1(x=0.5、1、2,摩尔分数,%)合金,研究了合金的微观组织特征及力学性能。结果表明,流变挤压铸造能有效细化合金的微观组织。合金的基体组织由尺寸较大的α1-Mg和尺寸较小的α2-Mg晶粒组成,LPSO结构呈细小的网状结构均匀地分布在晶界处,LPSO结构的含量越低,其细化效果越明显。随着挤压压力增大,合金中LPSO结构的厚度越来越小,当压力达到100MPa后,厚度变化趋缓。与常规重力铸造相比,流变挤压铸造能有效提高合金的力学性能,特别是伸长率。在400MPa下的流变挤压铸造Mg96.9Zn1Y2Zr0.1合金的抗拉强度和伸长率较重力铸造下分别提高了19%和170%。     

添加重熔料后ZL205A合金的组织与性能

通过向ZL205A合金铸锭中添加不同比例的重熔料,进行重熔、浇注.对利用ZL205A合金组织遗传性细化合金品粒、提高合金力学性能进行初步研究.结果表明,ZL205A合金添加不同含量重熔料后,合金组织均有所细化;合金性能随着重熔料含量的增加先增大后减小.当重熔料含量为20%时,合金组织最为细小,晶粒尺寸达到33um左右:铸态力学性能达到最优,抗拉强度比原料ZL205A合金抗拉强度提高了11.6%,屈服强度和伸长率均较高,分别为87.6MPa及7.5%.进一步增加重熔料含量,合金组织粗化,力学性能逐渐恶化.     

混合稀土对压铸AZ91D合金的组织及力学性能的影响

研究了不同添加量的混合稀土对压铸AZ91D合金的组织和力学性能的影响。添加混合稀土后,常温力学性能没有明显改善。在100℃时,混合稀土含量为0.4%的压铸AZ91D合金的力学性能与不含混合稀土的试样几乎相等。在170℃时,混合稀土含量为0.4%的压铸AZ91D合金的抗拉强度、屈服强度及伸长率分别为206MPa、142MPa、26%,比不含混合稀土的压铸AZ91D试样的力学性能分别提高15.7%、10%及30%。这是因为添加适量的混合稀土后,形成热稳定性较高的强化相,增加了位错滑移阻力并阻碍裂纹扩展,镁基体中稀土元素起到固溶强化作用,从而提高镁合金的高温抗拉强度。     

Effect of pressure on microstructures and mechanical properties of Al-Cu-based alloy prepared by squeeze casting

A new high-strength aluminum alloy with better fluidity than that of ZL205A was developed. The effect of applied pressure during squeeze casting on microstructures and properties of the alloy was studied. The results show that the fluidity of the alloy is 16% and 21% higher than that of ZL205A at the pouring temperature of 993 K and 1 013 K, respectively. Compared with permanent-mold casting, mechanical properties of the alloy prepared by squeeze casting are much higher. The tensile strength and elongation of the alloy are 520 MPa and 7.9% in squeeze casting under an applied pressure of 75 MPa, followed by solution treatment at 763 K for 1 h and at 773 K for 8 h, quenching in water at normal temperature and aging at 463 K for 5 h. The improvement of mechanical properties is attributed to the remarkable decreasing of the secondary dendrite arm spacing(SDAS) and eliminating of micro-porosity in the alloy caused by applied pressure.     

Effect of rare earth on the microstructure and mechanical properties of as-cast Cu-30Ni alloy

Cu-30Ni-xRE (x = 0–0.213) alloys were prepared by a metal mould casting method. The effect of RE on the microstructure and mechanical properties of the alloys was investigated using optical microscope, scanning electronic microscope with energy-dispersive spectrometer, X-ray diffraction, and mechanical test. The results show that RE has obvious effect on refining dendrite structure and grain size, as well as on purifying the melting of Cu-30Ni alloy. With the increase of RE content, the ultimate tensile strength, yield strength, and elongation increase at first and then decrease after adding RE more than 0.095 wt.%. Cu-30Ni-0.095RE alloy possesses preferable mechanical properties, i.e., the ultimate tensile strength, yield strength, and elongation are 308 MPa, 125 MPa, and 51.2%, respectively. The microstructure and mechanical properties are worsened with increasing RE content more than 0.095 wt.%. The improvement of mechanical properties of Cu-30Ni-0.095RE alloy is attributed to RE refining microstructure and purifying the matrix.     

Al-Ti-C中间合金在ZL205A合金石膏型铸造中的应用

通过对石膏型铸造ZL205A合金添加不同含量的Al-Ti-C中间合金,研究了Al-Ti-C中间合金对ZL205A合金组织和性能的影响。结果表明,当Al-Ti-C中间合金添加量为0.7%时,ZL205A晶粒的细化效果最好,晶粒尺寸达到82μm。经过T5处理,添加0.7%的Al-Ti-C中间合金的ZL205A合金的抗拉强度为456MPa,伸长率达到8.2%,比未处理的ZL205A合金性能有了显著提升。     

7075铝合金传动轴空心轴身的挤压铸造工艺研究

采用挤压铸造工艺制备了7075高强铝合金传动空心轴缩比件,并对其轴身的组织性能进行了研究.结果表明,在浇注温度与模具温度分别为700 ℃与250 ℃条件下,随着挤压压力的增大,可逐渐获得结构致密、晶粒细小、力学性能优异的挤压铸造高强铝合金管坯,当压力为160 MPa时,管坯的微观组织呈树枝状、颗粒状与蔷薇状相混合的结构形态,且其抗拉强度及伸长率均达到最大值,分别为545 MPa与8%;断口分析发现,随着挤压压力的增大,7075铝合金经挤压后的断裂模式由解理断裂逐渐转变为塑性断裂.     

不同铸造方法对7075铝合金热导率及力学性能的影响

采用金属型铸造、液态挤压铸造和半固态挤压铸造方法制备了7075铝合金,研究了不同铸造工艺对7075铝合金热导率与力学性能的影响。结果表明,金属型铸造晶粒粗大,产生枝晶偏析降低塑韧性,抗拉强度及伸长率最小,分别为121 MPa和2.78%,但晶粒粗大使热量传导路径宽,对电子散射几率小,电子的平均自由程较长,热导率相对较高,达到了139.67W/(m·K);液态挤压铸造晶粒细化,抗拉强度和伸长率分别为239MPa和5.75%,但晶粒细小且枝晶臂较多,对电子散射程度大,热导率最低,为120.94W/(m·K);半固态挤压铸造的晶粒致密细小且圆整,抗拉强度及伸长率最高分别达到248MPa和7.46%,且热导率为126.07W/(m·K)。     

Improvement of microstructure,mechanical properties,and corrosion resistance of WE43 alloy by squeeze casting

The WE43 magnesium alloy was prepared by squeeze casting, and the influence of squeeze casting parameters on mechanical properties and corrosion resistance was studied and compared with gravity casting. The gravity cast WE43 alloy shows uneven grain size distribution, and some grains even greater than 90 µm. While, the grain size of the squeeze cast WE43 alloy is mainly distributed in 20–50 µm. The Mg₁₂Nd₂Y phase morphology changes from large lamellar to strips after squeeze casting, whereas Mg₂₄Y₅ phase exhibits no obvious change. The yield strength, tensile strength, and elongation of the gravity cast WE43 alloy are 127 MPa, 157 MPa, and 6%, respectively, and 145 MPa, 193 MPa, and 9.1% for squeeze cast alloy. For the squeeze cast WE43 alloy, the average corrosion rate is 0.6056 mm·year⁻¹ according to immersion test results, and according to electrochemical measurements, the corrosion current density is 78.13 µA·cm⁻², which is better than that of the gravity cast WE43 alloy. Compared with gravity casting, the grains and second phase of the WE43 alloy by squeeze casting are refined, and the mechanical properties and corrosion resistance are improved. This may expand the applications of the WE43 alloy.

     

Microstructure and mechanical properties of extruded Mg-6.5Gd-1.3Nd-0.7Y-0.3Zn alloy

The Mg-6.5Gd-1.3Nd-0.7Y-0.3Zn alloy ingot and sheet were prepared by casting and hot extrusion techniques,and the microstructure,age hardening behavior and mechanical properties were investigated.The results show that the as-cast alloy mainly containsα-Mg solid solution and compounds of Mg5RE and Mg24RE5(RE=Gd,Y and Nd)phases.The grain size is refined after hot extrusion,and the Mg5RE and Mg24RE5 compounds are broken during the extrusion process.The extruded alloy exhibits remarkable age hardening response and excellent mechanical properties in the peak-aging state.The ultimate tensile strength,yield strength and elongation are 310 MPa,201 MPa and 5.8%at room temperature,and 173 MPa,133 MPa and 25.0%at 300℃,respectively.     

Influence of Sr on microstructure and mechanical properties of ZL114 cast alloy

In the present work,the effects of trace element Sr on the microstructure,tensile properties,fractography and morphology of the eutectic Si of ZL114A (Al-7Si) cast alloy were investigated.The cast ZL114A aluminum alloy was prepared using a metal mold,and then heat treated with the T6 technique.The test results of mechanical properties show that modification element Sr can improve significantly the ultimate tensile strength,elongation and hardness of the ZL114A-T6 aluminum alloy.By adding 0.04％Sr,the values of the tensile strength Rm,elongation A and hardness HB increase from 230 MPa,1％ and 65 to the maximum of 305 MPa,8％,and 100,respectively.SEM analysis indicates that the near tensile fracture surface on longitudinal section of the ZL114A-T6 alloy reveals a transgranular fracture mode without Sr modification,while the tensile fracture is an intergranular fracture mode after Sr modification.The morphology of the eutectic Si phase is changed from acicular to fine fibrous.     

热处理对半固态A356铝合金挤压铸件组织与性能的影响

将低温浇注制备的半固态A356铝合金坯料加热至半固态浇注、挤压成形。采用正交试验法研究了固溶、时效对半固态A356铝合金挤压铸件组织与力学性能的影响。结果表明,时效时间对抗拉强度、屈服强度、伸长率影响最大,且都是随着时效时间增长先上升后下降;试验6获得较好的综合力学性能,其抗拉强度、屈服强度、伸长率分别为340 MPa、325 MPa、9.56%。     

Effect of heat treatment on microstructure and properties of semi-solid squeeze casting AZ91D

Semi-solid AZ91D magnesium alloy billets were prepared by near-liquidus heat holding. Semi-solid squeeze casting was conducted at 575, 585 and 595 ℃, respectively, with 1 mm·s~(-1) squeeze speed. The semisolid squeeze casting AZ91D samples were heat treated by T4(solution at 415 ℃ for 24 h) and T6(solution at 415 ℃ for 24 h + 220 ℃ for 8 h) processes, respectively. The microstructure and mechanical properties of the alloy in different states were investigated by means of OM, SEM and tensile testing machine. The results show that compared to as-cast alloy, the grain size of the semi-solid squeezed AZ91D decreased significantly, and with the increase of semi-solid squeeze temperature, the grain size of AZ91D increased. The grains of the alloy were refined by T4 treatment, and further refined by T6 treatment. T6 treatment greatly improved the tensile strength, elongation, and hardness, but did not significantly improve yield strength. After 575 ℃ squeeze casting and T6 treatment, the ultimate tensile strength(UTS) reached 285 MPa, the elongation reached 13.36%, and the hardness also reached the maximum(106.8 HV), but the yield strength(YS) was only 180 MPa. During the process of semi-solid squeeze casting and heat treatment, the matrix grain was refined and a large number of precipitated and secondary precipitated phases of Mg_(17)Al_(12) appeared. Both the average size of matrix grain and secondary precipitated phase decreased, while the volume fraction of secondary precipitated phase increased. All these resulted in high tensile strength, elongation and hardness.