锌侣合金热型连铸定向凝固的组织和性能

热型连铸锌铝合金线材定向凝固实验研究结果表明：热型连铸锌铝合金线材显微组织为定向生长的平行柱状枝晶。共晶合金ZA5共晶的枝晶都由多层片状β和η两相构成,过共晶合金的组织为先共晶相枝晶和枝晶间共晶,与普通铸造材料相比,抗拉强度和硬度显著提高,但伸长率有所下降。从ZA5到ZA12、ZA22和ZA27,强度依次递升,其中ZA27的综合力学性能最佳。退火可使枝晶偏析减少,虽然强度略有降低,但塑性可得到改善。     

锌铝合金热型连铸定向凝固的组织和性能

热型连铸锌铝合金线材定向凝固实验研究结果表明 :热型连铸锌铝合金线材显微组织为定向生长的平行柱状枝晶。共晶合金ZA5共晶的枝晶都由多层片状β和η两相构成 ,过共晶合金的组织为先共晶相枝晶和枝晶间共晶 ,与普通铸造材料相比 ,抗拉强度和硬度显著提高 ,但伸长率有所下降。从ZA5到ZA12、ZA2 2和ZA2 7,强度依次递升 ,其中ZA2 7的综合力学性能最佳。退火可使枝晶偏析减少 ,虽然强度略有降低 ,但塑性可得到改善     

热型连铸L401铝合金焊丝组织及其堆焊层的耐磨性

利用热型连铸法(OCC),拉铸出4mm表面光滑的铝合金线材.以该线材为焊料,用钨极氩弧焊堆焊ZL117,并进行耐磨性试验.用金相显微镜,XRD衍射仪并结合相图分析线材和焊接接头组织.结果表明,热型连铸L401铝合金线材显微组织由定向生长的近平行柱状枝晶α-Al和枝晶间二元共晶(α-Al Si)和三元共晶(α-Al Si CuAl2)组成.由于堆焊层中含有大量CuAl2和Si相,堆焊层的硬度显著提高,其耐磨性是ZL117的43倍.     

过共晶Cu-Cr合金定向凝固组织中α相的形成机制研究

考察了Cu-1.7%Cr过共晶合金的定向凝固组织,对过共晶组织中出现亚共晶合金的初生α相的生长进行了探讨.研究表明:Cu-1.7%Cr过共晶合金定向凝固组织由初生β相、α相和(α-β)共晶组成;α相和(α+β)共晶的成分较大偏离平衡相图中的各相成分;初生β相分布在α相基体上.Cu-1.7%Cr凝固组织中α相的形成是非平衡凝固过程中枝晶α相和共晶相之间竞争生长的结果.α相是一种非平衡凝固组织,(α+β)共晶是偏离了平衡共晶成分的伪共晶组织.随着冷却速率的增加,α相的形貌尺寸减小,而数量有所增加.     

时效5年的触变成形ZA27合金微观形貌观察

通过OM、SEM和XRD，对触变成形并经5年自然时效的ZA27合金的微观组织进行了观察。结果表明：ZA27合金是由富Al枝晶和枝晶间的共晶组织组成。经触变成形和自然时效后的ZA27合金由球状初生粒子α′相、晶间的二次凝固组织及半固态成形时没有凝固完全的小液池组成。共晶方式主要为离异共晶及其中“蜂窝”状棒状共晶，部分区域出现不规则层片共晶组织。ZA27合金通过随后的冷却和自然时效过程，经过了一系列的相变，β相发生胞状分解，形成规则的共析（α＋η）层片组织或是不规则的复杂形状组织，从一些层片区域逐渐向低铝的α′相区域中心生长为粗大的层片组织，当其生长被α′相中心的连续分解所阻挡时，致使其芯部形成细小的（α＋η）颗粒组织。     

铝含量对热浸镀锌合金耐蚀性的影响

采用光学显微镜、电化学测试、SEM等方法研究了Zn-4Al,Zn-5Al和Zn-6Al热浸镀锌合金的显微组织和耐蚀性。结果表明,Zn-4Al合金由Zn-Al层片状共晶组织和大量的初生β-Zn相枝晶组成,Zn-5Al合金为Zn-Al共晶组织加少量的初生β-Zn相组成,Zn-6Al合金为初生的块状α-Al相和Zn-Al共晶组织组成,块状α-Al相周围的共晶组织多为颗粒状。Zn-5Al合金的自腐蚀电流密度J_corr最小,极化电阻R_p最大,合金表现出最好的耐腐蚀性。Zn-4Al和Zn-5Al合金是由初生的β-Zn相被优先选择腐蚀,Zn-6Al合金是由块状的α-Al相周围的共晶组织被优先选择腐蚀。     

热型连铸Mg-Al共晶合金线材的组织研究

利用热型连铸法（OCC）,成功拉制出φ5 mm的Mg-Al共晶合金线材。采用光学显微镜观察了热型连铸线材的微观组织。结果表明：热型连铸线材主要由沿水平拉制方向排列的柱状共晶组织（α-Mg＋β-Mg17Al12）构成。共晶组织形态由大量的层片状与少量的棒状构成。     

过共晶Cu—Cr合金定向凝固特性研究

考察了Cu-1.7%Cr和Cu-5.6%Cr过共晶合金的定向凝固组织.实验表明:Cu-1.7%Cr和Cu-5.6%Cr过共晶合金定向凝固组织是由初生β相、α相和(α+β)共晶组成;α相是基于竞争生长机制的一种非平衡凝固组织.凝固速度和成分对初生β相生长形态产生显著影响.在Cu-1.7%Cr合金中,初生β相生长为等轴颗粒状,且受凝固速度的影响不大.在Cu-5.6%Cr合金中,随着凝固速度的增加,初生β相的生长形态经历了树枝状到等轴颗粒状的演变;α相包裹树枝状的初生β相生长,形成了类似"包晶"结构的微观形貌特征;颗粒状的、均匀分布的初生β相有利于α相的定向生长.降低合金成分和提高凝固速度有助于获得最佳组织形态的复合材料.     

液固两相区等温热处理对ZA101枝晶形貌的影响

本文研究了液固两相区等温热处理对合金ZA101枝晶形貌的影响。试验分析了不同加热温度、保温时间和加热速度对其枝晶组织的影响。结果表明，经等温处理的ZA101合金组织形态将由枝晶向非枝晶转变，并最终生产成本为适合半固态加工的细小近球状初生相组织；加热速度的增加有助于提高其初生相组织的圆整度。     

基于微观测量技术的Cu-10.25%Mg过共晶合金定向凝固过程中的枝晶形貌分析

采用连续切片三维重构技术,以C15结构的Laves相Cu2Mg为研究对象,研究Cu-10.25%Mg过共晶合金定向凝固过程中初生相Cu2Mg的三维枝晶形貌。结果表明,其二次侧枝具有"板条"、"棱面"和"八面体"的形态,三维截面组织能够较好的反映初生相Cu2Mg的枝晶形貌,共晶组织填充了一次枝晶干和侧枝之间存在的空隙。     

MICROSTRUCTURE ANALYSIS AND MECHANICAL PROPERTIES OF Zn—Al ALLOY ROD PRODUCED BY HEATED MOLD CONTINUOUS CASTING

The new technology of continuous casting by heated mold was used to produce directional solidification ZA alloy lines to eliminate the inter defects of these lines and increase their mechanical properties. The results are as follows: (1) The microstruc-ture of the ZA alloy lines is the parallel directional dendritic columnar crystal. Every dendritic crystal of eutectic alloy ZA5 was composed of many layer eutectic β and η phases. The micro structure of hypereutectic ZA alloys is primary dendritic crystal and interdendritic eutectic structure. The primary phase of ZA8 and ZA12 is β, among them, but the primary phase of ZA22 and ZA27 is a. (2) Through the test to the as-cast ZA alloy lines made in continuous casting by heated mold, it is found that the tensile strength and hardness increase greatly, but the elongation decreases. With the increase of aluminum amount from ZA 5 to ZA 12, ZA22 and ZA27, the tensile strength increases gradually. ZA27 has the best comprehensive mechanical properties in these     

高压凝固ZA43合金的非平衡组织

研究了高压凝固条件下ZA43合金凝固组织的变化。高压凝固ZA43合金的组织明显变细，没有形成粗大的树枝晶，分布随机，形状各异，部分横截面类似于胞晶的粒状结构，共晶相呈均匀细小的蠕虫状结构。高压增加了溶质原子在固溶体中的固溶度，减少了枝晶偏析。讨论了高压对凝固组织的影响。     

均匀化处理对ZA35-0.3Zr合金组织及性能的影响

为了探索均匀化处理对ZA35-0.3Zr合金组织和性能的影响规律,通过组织分析、力学性能、电化学性能测试,确定了ZA35-0.3Zr合金均匀化处理的适宜温度和时间。结果表明,ZA35-0.3Zr合金枝晶偏析明显,晶界上Cu富集严重,存在非平衡β相。随着均匀化处理时间增加,ZA35-0.3Zr合金中CuZn5相逐渐消除,β相共析分解程度加大。对合金进行370℃×12h均匀化处理后,晶界处CuZn5相消除,枝晶偏析大大减少,同时非平衡β相基本消除,抗拉强度为306MPa,伸长率为7.35%。在3.5%的NaCl溶液中,开路电位与未均匀化处理合金相比变正,腐蚀电流密度减小了33.1%,耐腐蚀性增强。ZA35-0.3Zr合金适宜的均匀化处理工艺为370℃×12h。     

Effect of specific pressure on microstructure and mechanical properties of squeeze casting ZA27 alloy

The effect of specific pressure on the microstructure and mechanical properties of ZA27 squeezed castings with high height-to-thickness ratio was studied. The results of DTA and SEM show that at high specific pressure the eutectic reaction of squeeze casting ZA27 alloy is restrained, and the final solidified structure is (η+ε) phases instead of eutectic phase (β+η+ε). At the same time, the primary reaction is promoted in squeeze casting ZA27 alloy solidified at high pressure, and the fine microstructure is obtained with the increase of pressure. Al and Cu elements are homogeneously distributed in matrix of squeeze casting ZA27 alloy. The homogenously distributed high-density fine ε phase can effectively hinder dislocation motion, and then the strength and plasticity of squeeze casting ZA27 alloy are increased.     

Microstructure and mechanical properties of ZA62 based magnesium alloys with calcium addition

As-cast microstructure and mechanical properties of Mg-6Zn-2Al-0.3Mn (ZA62) alloys with calcium addition were investigated.The as-cast microstructure of the base alloy ZA62 consists of the α-Mg matrix and eutectic phase Mg51Zn20.The Mg51Zn20 eutectic was gradually replaced by MgZn phase and Mg32(Al,Zn)49 phase when calcium is added into the base alloy.Further addition of calcium leads to the increase of grain boundary phases and formation of a new quaternary Mg-Zn-Al-Ca eutectic compound.In comparison with the base alloy,the increase of calcium addition to the base alloy results in the reduction of both strength and ductility at ambient temperature,but increase at elevated temperatures due to the thermal stability of Ca-containing phases.At elevated temperatures,the creep resistance of ZA62 based alloys containing calcium is significantly higher than that of AZ91 which is the most commonly used magnesium alloy.     

Effect of rare earths on phase transformation in as-cast ZA27 alloy dur-ing compressive creep

The effect of the mixed rare earths of Ce on the phase transformation in as cast ZA27 alloy during compressive creep was investigated under 37 MPa and at 160℃ by X-ray diffraction technique and SEM. The results showed that the as cast microstructure of ZA27-RE alloy consisted of a dendritic Al-rich a' surrounded by Zn-rich β' phase, interdendritic ε phase and Zn-rich η phase together with a complex Z phase which was a complex constitute compound, (RE,Cu)Al5Zn16, dispersed in crystal interfaces or branch crystal interfaces and stable during compressive creep test at 160'C. The phase transformations of ZA27-RE alloy, decomposition of β' phase and four transformation, were delayed by the addition of rare earths, also the lamellar structure and the spheroidized structure in ZA27-RE alloy were finer than in ZA27 alloy during compressive creep test at 160℃ at the same creep time, and the compressive creep resistance of ZA27-RE alloy was higher than that of ZA27 alloy.     

热处理对挤压铸造ZA43—Mn合金组织和性能的影响

研究了热处理对冲头式挤压铸造ZA43-Mn合金显微组织和力学性能的影响。结果表明：挤压铸造ZA43-Mn合金的时效处理使α和β相分解,枝晶偏析减轻,富锰相碎化与钝化,可提高其塑性（δ5=18%）。固溶处理使富锰相和富铜相分解,基体内二次相弥散析出,晶间组织形态和分布改善,可获得较高强度的铸件（δb=510MPa)。     

Characterization of Microstructure of Permanent Mold Cast Zinc Alloy ZA27

The microstructure of permanent mold cast zinc alloy ZA27 was examined by SEM and TEM after natural aging for 18 months. It was found that the primary α‘ phase, peritectic and eutectic β phases all decomposed into the equilibrium well-formed α η lamellae or irregular α η structure through cellular reaction. The cell colonies nucleated on the interdendritic eutectic η layer and grew into the primary dendrites, thus first making the β phase in the dendrite edges decompose, and then the α‘ phase in the dendrite cores. The products from the α‘ phase appeared in regular lamellae rather than irregular particles. In addition, a fine, dense transitional phase α‘m containing 27.8 mass% AI, with a fcc crystal structure and lattice parameter of about 0.4013nm, formed in α lamellae. Copper was preferentially concentrated in Zn-rich η phase and existed in the form of Cu-rich ε phase (CuZn4) particles, with hcp crystal structure and parameters a=0.274nm,c=0.429nm and c/a=1.567.     

Zr-C过共晶合金的显微组织

采用SEM和XRD对Zr-C过共晶合金的显微组织进行了研究。低倍下Zr-C过共晶合金的显微组织为在α-Zr基体上分布着树枝晶状和颗粒状的ZrC,而不是在共晶组织基体上分布着ZrC先共晶相。在高倍下树枝晶状的ZrC呈层片状结构。背散射电子相表明,ZrC层片间存在α-Zr。