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采用“多向锻造+挤压+在线水冷”技术制备出截面尺寸为290 mm×230 mm的Mg-8Al-1Zn(AZ80,质量分数,%)合金棒材,沿横截面的230 mm方向(ND)对棒材进行冷压缩,压下量约为20 mm,冷压缩导致横截面心部(C)产生大量变形孪晶,而表层(O)的孪晶较少。研究了形变孪生对力学性能和析出反应的影响。沿挤压方向(ED)、截面的290 mm方向(TD)和ND 3个方向从C和O切取拉伸试样。测试结果表明:棒材的室温力学性能存在显著的各向异性和表里不一致性。挤压材的O沿ED(ED-O)具有最高的强度,其性能为:RP0.2、Rm和A分别为295 MPa、401 MPa和10%,而C沿ND(ND-C)具有最低的强度,其性能为:RP0.2、Rm和A分别为164 MPa、273 MPa和7%。织构是导致各向异性和表里不一致性的主要原因,而变形孪生对织构有重要影响。冷压缩之前,C存在2种取向,即:[0001]_(Mg)∥TD和[0001]_(Mg)∥ND;冷压缩后,O的织构几乎没有变化,而变形孪晶导致C的织构发生重大转变,[0001]_(Mg)∥TD取向被大幅弱化,而[0001]_(Mg)~∥ND取向被大幅加强。合金155℃/7 h时效后,变形孪晶内析出了β连续析出相,这些孪晶内的β析出相比层片状β非连续析出相更加细小弥散。
The Mg-8Al-1Zn (AZ80, mass fraction,%) alloy bar with a cross section of 290 mm × 230 mm was prepared by the technique of “multi-directional forging + extrusion + online water cooling” (ND) to cold compress the bar with a reduction of about 20 mm. Cold compression results in a large amount of deformed twins in the cross-sectional core (C) and less twins in the surface (O). The effect of deformation twin on mechanical properties and precipitation reaction was studied. Tensile specimens were cut from C and O along the direction of extrusion (ED), 290 mm of cross section (TD) and 3 directions of ND. The test results show that there are significant anisotropy and inconsistency of the room temperature mechanical properties of the bar. The O-edge along the ED (ED-O) of the extruded material has the highest strength with the properties of RP0.2, Rm and A of 295 MPa, 401 MPa and 10% respectively, while C has the lowest ND The properties are: RP0.2, Rm and A respectively 164 MPa, 273 MPa and 7%. Texture is the main cause of anisotropy and inconsistency in the surface, while the deformed twin has an important effect on the texture. Before cold compression, there are two orientations of C, namely: [0001] _ (Mg) ∥TD and [0001] _ (Mg) ∥ND; After cold compression, the texture of O shows little change and the deformation twin leads to C (0001) _ (Mg) ∥TD orientation is significantly weakened, and the [0001] _ (Mg) ~ ∥ND orientation is greatly enhanced. After aging at 155 ℃ for 7 h, the β-precipitated phase precipitated in the deformed twin, and the β precipitates in these twin crystals were more finely dispersed than the laminar β non-continuous precipitates.