(甘肅工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院, 蘭州 730050)
摘 要: 研究了等溫?zé)崽幚頊囟群捅貢r間等工藝參數(shù)對AZ91D鎂合金半固態(tài)組織演變和成形性的影響。 結(jié)果表明, 半固態(tài)等溫?zé)崽幚砜梢詫⑵胀ń饘傩丸T造的AZ91D鎂合金錠中的枝晶組織轉(zhuǎn)變?yōu)榍蛐尉Я＝M織，其演變過程為：在升溫過程中晶界處部分γ相先發(fā)生溶解, 隨著溫度的升高，剩余的γ相開始熔化，繼而δ相也發(fā)生熔化，并在等溫處理中逐漸演變?yōu)榍驙? 保溫溫度越高，半固態(tài)重熔和δ相演變過程越快，保溫溫度過高或保溫時間過長，試樣易發(fā)生變形， 同時，球狀晶粒也容易趨于長大。 AZ91D鎂合金半固態(tài)成形所需的最佳工藝條件為加熱溫度570℃左右，保溫時間25~35min; 或加熱溫度580℃左右，保溫時間15~20min。
關(guān)鍵字: 鎂合金; 半固態(tài)等溫?zé)崽幚? 組織演變; 半固態(tài)成形
（College of Materials Science and Engineering, Gansu University of Technology,
Lanzhou 730050, China）
Abstract:The effects of isothermal temperature and holding time on microstructure evolution and forming of AZ91D magnesium alloy in semi-solid state were studied. The results show that the semi-solid isothermal heat-treatment can turn the dendritic structure of AZ91D magnesium alloy by permanent mould cast into spheroids. The process is as following: during the increasing of temperature, the partialγphase at grain interface of eutectic structure is dissolved first; then with the further increasing of temperature, the residualγ phase and the δ phase begin to remelt successively and theδ phase gradually evolves into spheroidal shape during the holding. The higher the isothermal temperature, the faster the semi-solid remelting of samples and the δ phase evolution process. When the isothermal temperature is much higher or the holding time is much longer, the samples are susceptible to deformation. And the spheroidal structure is also susceptible to grow up. The best semi-solid structure for semi-solid-forming can be obtained at about 570℃ and the holding time about 30~45min, or about 580℃ and the holding time about 15~25min.
Key words: magnesium alloy; semi-solid isothermal heat-treatment; microstructure evolution; semi-solid forming
