Precipitation behaviors, texture and tensile properties of an extruded Mg-7Y-1Nd-0.5Zr (wt%) alloy bar with large cross-section
Precipitation behaviors, texture and tensile properties of an extruded Mg-7Y-1Nd-0.5Zr (wt%) alloy bar with large cross-section
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DOI：
10.1016/j.msea.2016.12.076
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发表时间：
2017-02
期刊：
影响因子：
6.4
通讯作者：
G. Shi;Kui Zhang;Xing-gang Li;Yongjun Li;M. Ma;Jiawei Yuan
中科院分区：
文献类型：
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作者：
G. Shi;Kui Zhang;Xing-gang Li;Yongjun Li;M. Ma;Jiawei Yuan
采用硬度测试、拉伸试验、光学显微镜（OM）、扫描电镜（SEM）、透射电镜（TEM）、电子背散射衍射（EBSD）、X射线衍射（XRD）宏观织构分析等方法，研究了230 mm×140 mm大截面Mg-7 Y-1 Nd-0. 5 Zr（wt%）（WE 71）合金挤压棒材的析出行为、织构和拉伸性能。采用“多向锻造+挤压+在线淬火+T5时效”工艺进行工业化生产。在200 ° C和235 °C的T5时效期间显示出完全不同的时效硬化行为。在前100 h内，235 °C下的T5时效使硬度增加约13%，而200 °C下的T5时效导致硬度增加47%。在200 °C的T5时效过程中，β′析出物在基体中以高数量密度均匀形核;而在235 °C的T5时效过程中，β′析出物在离散和稀疏的位错上不均匀形核，导致β′析出物在基体中呈链状排列，并具有较宽的无析出区。XRD宏观织构测试结果表明，WE 71棒材的织构强度远低于Mg-8Al-0. 5 Zn-0. 15 Mn（wt%）（AZ 80）棒材，其最大织构强度分别为17和14，最大织构强度在外层（O）和中心（C）均在3左右。EBSD显微织构测量表明，C和O的最大织构强度分别为5.3和3.5。O比C具有更高的拉伸性能，这是因为C中存在更多的未动态再结晶晶粒，从而具有更大的平均晶粒尺寸。室温拉伸时，O方向（艾德）的拉伸性能最好，极限拉伸强度（Rm）为368 MPa，伸长率（A）为5%; C方向（ND）的拉伸性能最差，Rm为255 MPa，伸长率（A）为2%。在200 °C拉伸时，强度没有太大下降; O中的艾德仍然具有最好的拉伸性能，即Rm=326 MPa，A= 7%，而C中的ND仍然具有最低的拉伸性能，即Rm=263 MPa，A= 4%。
Precipitation behaviors, texture and tensile properties of an extruded Mg-7Y-1Nd-0.5Zr (wt%) (WE71) alloy bar with large cross-section of 230 mm×140 mm were investigated by hardness test, tensile test, optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD) macro-texture measurement. The bar was manufactured industrially through a procedure of “multi-direction forging (MDF)+extrusion+on-line quenching+T5 aging”. Totally different age-hardening behaviors are shown during T5 aging at 200 and 235 °C. In the first 100 h, T5 aging at 235 °C brings about 13% increases in hardness, while T5 aging at 200 °C results in 47% increase. During T5 aging at 200 °C, β′ precipitates homogeneously nucleate within the matrix with high number density; however, during T5 aging at 235 °C, β′ precipitates heterogeneously nucleate on discrete and sparse dislocations, resulting in chain-like arrangement of β′ precipitates with broad precipitate free zones in matrix. XRD macro-texture measurement illustrates that basal texture intensity of WE71 bar is much weaker than Mg-8Al-0.5Zn-0.15Mn (wt%) (AZ80) bar; the maximum basal texture intensities in the outer (O) and center (C) of WE71 bar are all about 3, while those of AZ80 bar are 17 and 14, respectively. EBSD micro-texture measurement demonstrates that the maximum texture intensities of C and O are 5.3 and 3.5, respectively. O has higher tensile properties than C because there are more un-dynamic-recrystallization (un-DRX) grains and thus larger average grain size in C. While stretching at room temperature (RT), extrusion direction (ED) in O has the best tensile properties, i.e. ultimate tensile strength (Rm)=368 MPa, elongation (A)=5%, and normal direction (ND) in C has the lowest tensile properties, i.e. Rm=255 MPa, A=2%. While stretching at 200 °C, strength does not degrade much; ED in O still has the best tensile properties, i.e. Rm=326 MPa, A=7%, and ND in C still has the lowest tensile properties, i.e. Rm=263 MPa, A=4%.